Alligator weed is a threat to waterways and irrigation systems as well as other places with access to high water levels. It grows in both land and water and can adapt to a wide range of environmental conditions. To make matters worse, it can withstand several control measures, including chemical means. As such, it continues to pose a significant problem in the areas in which it establishes.

One of the most affected regions is Australia, and for most of this article, the emphasis will be on this country. The introduction of this weed took place in the twentieth century. Ever since that time, it has spread, taking over hundreds of acres in both land and water sources. It continues to do so at a fast rate, and it is thus necessary to keep it from spreading by containing the outbreaks. People need to work on controlling the growth of large infestations while removing the small ones.

This article will cover the nature of this plant, how it impacts the environment, and ways to deal with it. It will act as a guide for anyone with an alligator weed infestation. Information provided here will go a long way in raising awareness and thus salvaging affected areas.

What is alligator weed?

This plant is perennial and can grow in water sources as well as land. It is thus highly adaptable to the prevalent conditions and can easily take over irrigation systems, wetlands, and other water sources. As of now, it has negatively affected areas in which it has been introduced. A key example of this would be Australia, where authorities are grappling with this growing issue. Worldwide, it continues to spread, and so do its negative impacts.

This article will focus on Australia, where this weed has proven to be a menace. This plant is native to South America, and it found its way to Australia back in the ‘40s. Theories point to an introduction as a result of the transportation of cargo from ships. This spread is likely to have taken place during the Second World War. Initially, studies pointed at an introduction resulting from ship ballast. With the last reported ballast dumping taking place thirty years to the reporting, this introduction is not likely.

The alligator weed is a perennial herb that grows in aquatic, terrestrial and semi-aquatic habitats. It adapts to a wide range of climatic conditions, including but not limited to tropical and temperate regions.

Identification of alligator weed

Given its adverse effects on places in which it establishes, you should know how to identify this weed:


The stems which branch out or grow singly can either grow vertically or horizontally. They turn hollow when mature. Vertical stems have dark green hues, and they can reach heights of over two meters. They can grow longer when they have the support of other species. Horizontal stems have light green to reddish hues, and their nodes can thicken while buried in the sediment. On each node, a pair of leaves emerge.


Dark green leaves in spear shapes and acute tips emerge on opposite sides of the stem in pairs. They are waxy and sessile, and their shapes and sizes vary based on the growing conditions. They can reach lengths of between two and twelve centimeters and are half to four centimeters wide.


The underground filamentous roots are quite extensive, and they develop from nodes on the stems. Their texture and length highly depend on the conditions in which they grow. In water, they are fine and short, whereas, in the soil, they become starchy and thick. The taproot systems can get to depths of half a meter in the soil in most cases. However, where the conditions prove to be ideal, the roots can reach depths of more than a meter. As such, removing alligator weed once established can be quite a difficult process.

When the plants grow in semi-aquatic and terrestrial conditions, they store food reserves in the roots. In this way, the weed can survive even when the conditions are dry for an extended period. Some people state that these plants have underground rhizomes. However, it is not clear if these are rhizomes or thickened roots or stolons. They could also be old stems that have been in the ground for long or emerging shoots yet to reach the surface.


The alligator weed is a flowering plant that produces whitish flowers that exist on long stalks. Each flower has a ball shape and has numerous other flowers in it. The flowering takes place towards the end of summer, where the plants grow in water. In soil, the flowering can take place at the start of mid or summer. In native regions, seed production is possible, leading to the development of new plants. That is not the case in introduced areas such as Australia.

The features of this plant are quite distinctive, and this aids a great deal in telling it apart from other species. Key features include mature hollow stems, white ball-like flowers, and opposite leaves, among others.

Alligator weed Look-Alikes

More often than not, people will not realize that they have a weed problem until it is too late. This situation is quite common where a weed bears a striking resemblance to other plants. With the alligator weed, there are tens of species that are similar to it, some of which are native. Here are some of the key look-alikes:

Native Alternanthera species

These plants are native to Australia, and they do not harm the environment in their isolated or widespread distributions. They also have opposite leaves, as you would find in the alligator weed. However, their sessile flowers do not exist on stalks, as is the case with this invasive weed. They include Alternanthera denticulate, Alternanthera nana, Alternanthera nodiflora, and Alternanthera Angustifolia.

Similar Species

These are species that are native to Australia as well as other countries and have established in Australia. They include water primrose that is native to South America. It has alternate leaves and produces single yellow flowers. The blue water speedwell with finely toothed leaf margins is native to Eurasia, and it produces pale blue flowers.

The buffalo spinach has serrated leaf margins, and its flower heads exist on leaf axils. Slender knotweeds have alternating leaves with flowers available in a wide range of hues, including purple, pink, and white. Gomphrena weed is native to South America, and it features greenish-white flowers that occur at the end of branches.

The Hygrophila, which is native to the Americas, also has opposite leaves. It differs from the alligator weed in that its white flowers exist in inconspicuous whorls at the leaf-stem junctions. The Senegal tea plant features ribbed stems and toothed margins along its leaves. Sessile joyweed is a noxious weed in the United States, and it features flowers in clusters that are devoid of stalks.

With these distinguishing features in place, you can easily tell the alligator weed apart from other plants.

Alligator weed growth

The growth pattern of the alligator weed largely depends on where it grows and the conditions in play. What you see growing in water will be quite different from what you would come across on land. Not only will the sizes differ, but the plants will also have dissimilarities in their shapes and appearances. However, there are some similarities.

A good example would be in the active growing seasons. Generally, the plants will be erect during the summer before falling back when the weather gets cold. Also, the stands mainly comprise younger stems leaning on older ones for support.

Where does alligator weed grow?

The alligator weed can grow in aquatic, semi-aquatic, and terrestrial conditions as follows:

On land

When alligator weed grows on land, it creates dense stands with roots reaching deep into the soil. The plants form mats as they increase in density and can thus have roots and stems that are up to ten centimeters thick. As they do this, they create unfair competition and are, therefore, able to displace the native communities. These plants grow under conditions of harsh temperatures, minimal nutrients, and stiff competition. As such, they cannot grow at the same rate as those in the water, and this affects their appearance.

They have small leaves and grow more compactly than the plants in water. Compared to aquatic alligator weeds, terrestrial plants have leaves that are four times smaller. They also produce fewer flowers, resulting in a rate of 0.8 flowers on each stem, while aquatic plants average 1.0. The biomass of these plants is also quite low when compared to that of the plants in water.

However, they more than make up for this reduced biomass by developing extensive root systems. The roots can have biomass that is ten times more than what is above the ground — as such, pulling out these plants by hand may not be a viable control method. Compared to plants in water, the terrestrial root systems can be as much as seven times heavier.

Where this plant grows in the presence of water and nutrients, the growth rate determinants are temperature and growth rate. For plants on land, access to water might be a limiting factor. Also, the temperatures can be harsh, affecting the growth rate of the plant. For this reason, plants on water grow at a much faster rate compared to those on land. Where the weeds grow devoid of control measures, they can increase their density by as much as twenty percent each year.

In Water

The alligator weed depends on substrates or soils near the water to root. Once established, it forms an extensive system comprising stems, roots and leaves and spans over the water surface. In so doing, the plant creates a mat that can be more than a meter thick. In some cases, the mat can break away and exist far from where the plant established.

Where the conditions are ideal, the drifting mat can root in the substrate again or release fragments that develop into new shoots. The drifting and breaking away aid in the development of new plants away from the parent plant.

Plants growing in water have adequate access to moisture, and they face less competition. Also, the temperatures are not extreme, and the substrates provide sufficient nutrients for the plants. These plants will thus do better than those on land such that they can double in size within one growing season. It helps to note that they can also grow during the cold months.

In both cases

You are likely to come across this weed in waterways, floodplains, and waterway banks, as these environments provide the ideal conditions. Though it is not common, this plant can also grow in dry conditions. It has a preference for cool and warm climates and will mostly grow in areas with high rainfall in the warm months. Thanks to its food reserves, it can grow in areas with long dry periods.

It will also withstand a wide range of soils and saline conditions, enabling it to compete with most species. On land, it does so by creating dense mats that starve other plants of light and space. In water, the creation of blankets over the water surfaces ensures that other species lack light and nutrients. Alligator weed cannot, however, compete with water hyacinth, which is also a highly invasive aquatic weed.

When does alligator weed grow?

Alligator weed thrives in the presence of warmth and will thus do well when the conditions prove to be favorable. The growing season will depend on the area in which the plant establishes. In Australia, the warm months are between September and May. As the months get colder, the growth rates reduce and sometimes come to a stop. While the cold may kill what is above the ground, growth will continue as the underground system will remain in place.

Once a growing season passes, the plants lose their leaves and form a mat that encourages the growth of new shoots. The new stems arise from axillary and terminal buds in spring, and the process continues. In summer, the stems increase in density and thus develop new nodes. During this period, the growth rate peaks, and biomass increases at a fast rate.

How does alligator weed reproduce?

Outside its native range, studies show that it is highly unlikely that the alligator weed would produce viable seeds. As such, the growth results from vegetative propagation. In this way, if an alligator weed was to establish in a region, the chances are high that all other weeds would result from this parent plant. New shoots and roots develop from nodes on the stems or underground stems. Buds on the stems remain dormant until they have exposure to sunlight, then they grow into new plants.

A root fragment can lead to the development of a new plant. However, the rate of regeneration is still under investigation. As such, there is no telling what size of a fragment can lead to a new infestation. However, you should note that root fragments are resistant to drying out. You could leave them out to dry and dispose of them, only for the fragments to root. Also, they can withstand damage to a given extent, such as that from trampling. Disposing fragments is thus a tricky task, and there is a need for caution when undertaking the same.

Alligator weed threats

The weed reared its ugly head in the 70s by spreading at a fast rate and resisting control measures in place. It reproduced from fragments with ease, and this raised concerns as to its aggressiveness. As such, authorities had no choice but to label it as an invasive plant. At present, this weed is present in both land and water. Its effects are felt in recreational, commercial, and agricultural activities owing to its invasion of water channels.


Both the stems and root fragments of this plant can give rise to new plants. It is thus capable of reproducing and spreading at a fast rate, giving it the upper hand over native species. The spread can either be intentional, natural, or accidental as follows:


This spread occurs in the habitat, and it follows nature’s course.

A good example would be where plants experience a current or another form of disturbance. In this case, some fragments would break off from the parent plant. They would then float to another place where they could develop into new plants if the conditions proved to be ideal. On land, these weeds compete with other species for nutrients and light, and in doing so, they grow at a fast rate. Eventually, they become the dominant species and push other plants out of the habitat.


Accidental spread is also a common means of dispersal, and it is thus important that people exercise caution when handling this weed. Suppose a waterway has an alligator weed infestation, and people access the habitat by boat. They are likely to pick up fragments which they would spread over the water source, aiding the plant’s spread. Also, where you do not wash the boat after use and take it to another water source, the spread of this weed is possible. Other activities include the mowing of plants, using plant materials like mulch, and improper disposal.

Animals, too, play a part in the accidental spread of this weed. Where the animals have access to an infested water source, they are likely to pick up fragments on their body parts. They can then spread these parts over land or water. Animals such as cattle could also graze on the plants and spread the parts to other places. Note that the grazing of animals on this weed could be detrimental to their health.


How do people willfully spread the alligator weed? It comes about in several ways. For one, some people will cultivate the plant having mistaken it for other vegetables. They could thus offer the same to their friends who would plant the weed in their vegetable gardens.

Another means is through horticultural trade. People love the aesthetic value of this weed and will thus seek to use it in their aquariums and small ponds. While this trade may be illegal in some countries such as Australia, such may not be the case in other regions. This spread is thus likely.

Distribution of alligator weed

In Australia, which is the main focus of this article, this weed occupies more than four thousand hectares. Looking at this, one might think that this weed is not much of a problem. However, it has the likelihood of spreading through the region where control measures are not in place. The best way to describe the distribution of this weed would be regarding the level of the infestation. The infestation can either be widespread or isolated as follows:

In widespread outbreaks, this weed has been in existence for a long while, and it thus covers large tracts of land. The weed exists in dense stands and can spread with ease. A widespread infestation can cover tens of hectares, most if not all of which comprise the weed. In such places, eradication may not be an answer, and the best way to approach the infestation would be containment. In this way, people can reduce the spread of the weed and thus minimize its impacts before reducing the dense stands. The emphasis here should lie in containing the likely spread of the masses.

On the other hand, there are small and isolated infestations. These are newly introduced weeds that are yet to establish and start spreading at a fast rate. In this case, you can think of eradicating the weed and restoring the habitat to its previous state.

Have you heard of backyard infestations? These occur when people grow alligator weed in their homes without the knowledge of its impacts. Domestic cultivation has contributed significantly to the spread of this weed over the years. Such was the case in 1995 when an entomologist came upon this weed in a vegetable garden. The owner thought that the plant was mukunuwenna, which is a popular vegetable in the region. The similarity of this weed to palatable vegetables does not help matters, and it only encourages its spread.

Many studies took place after this discovery, and it became apparent that many people had planted this weed in their homes. People would give this weed to others who would plant it in their homes. They could also fragment the plant when cutting their lawns, aiding its spread. It thus became necessary to eradicate these backyard infestations, which posed a risk to farmlands and waterways. If you come across such an outbreak, prioritize containing it before moving on to eradication.

Authorities in Australia have worked hard to raise awareness as to the effects of this weed. They have also advocated for the growth of native species, which are as palatable and which have no severe environmental impacts. An excellent example of such a species is lesser joyweed that is native to the region. People in Asia can also grow this vegetable as it is native to the area.

Is it likely that the plant will spread further? Yes, alligator weed is a highly adaptable plant that can grow in varying conditions. Studies show that most non-arid areas are suitable for its growth in Australia, Asia, and the USA. Once the weed establishes in inland waters, it can move across vast distances, thus occupying many hectares in no time. For this reason, management practices have to come into play to contain and eradicate current infestations. And the way to do this is to spread awareness and deal with outbreaks as they occur.

Does the law play a part? Where authorities state that a plant is invasive, they put in measures to prevent its spread. It could be through the enactment of laws, prohibition of distribution, and bans, among other activities. In Australia, the sale and distribution of this weed are illegal. People have to work towards containing and eradicating infestations, and this aids in controlling its spread. Find out what laws are applicable in your area regarding the alligator weed and other invasive species.


It negatively impacts aquatic systems by blocking water channels and thus restricting water uses. It also affects the water properties and competes with native plants, threatening the ecological balance. Additionally, it alters the growing conditions in its favor to the detriment of the native species. The desirable plants thus reduce in numbers, and aquatic animals have to fend for food elsewhere.

The plants obstruct the flow of water, and people farming in the affected areas have to put up with little or no yields. This obstruction also serves as a threat to the neighboring communities as flooding is likely to take place. The destruction of property and loss of lives is a possibility with the establishment of this weed. It also causes sedimentation, which further increases the likelihood of flooding.

Communities living nearby have to come up with measures to deal with parasites as the weeds create breeding grounds for mosquitoes. They also have to put up with the eyesore, which results from the dense floating masses on the water.

On land, this weed lowers the value of agricultural and pasture lands. The productivity of these lands reduces, and farmers end up with minimal returns. The fragments released by this weed could get into crops and hay, thus contaminating them and reducing their value. Here are more effects as follows:


In Water

The alligator weed grows as a floating mat on the water surface. In this way, it has adequate access to light while shading out the native plants. The mats reduce light penetration into the water, and this creates anaerobic conditions that are unsuitable to desirable plants. Over time, the native species die off, leaving a monoculture of alligator weeds that continue to spread over the water source.

This weed has a fast growth rate and will thus spread over an area fast. As it does so, it increases the sedimentation in place and puts an area at risk of flooding. The barriers in place collect debris over time, further heightening the risk. These mats can also grow against structures, and where this happens, they keep water from flowing as it should. They also hinder people and animals from using the waterway, thus impeding economic activities.

Where this weed grows in an irrigated area, fragments can make their way to the farmlands. These fragments grow into new plants that take up nutrients intended for the farm crops. The weeds shade out the desirable plants and end up reducing the yield available to farmers. On top of all these, the fragments also contaminate the yield. Thus, they reduce the value fetched in an open market.

On Land

This weed is quite destructive on land. For one, if it grows in pasturelands, it will compete with the native species present for light and nutrients. Given its aggressive growth, it will displace the native communities, leaving the land full of weeds.

The palatability of this weed has been a cause for concern. While some people may try reducing an infestation by grazing animals on the weed, this is not advisable. This weed contains compounds that not only cause liver damage and skin lesions but also death in animals. It is thus best to keep cattle, sheep, and other animals away from the infested lands.

This weed infests desirable crops such as vegetables and rice, among others. When this happens, it displaces the crops while contaminating them and reducing their market value.


It costs a lot of money to deal with alligator weed once it has established in a habitat. A good example would be the Barren Box Swamp, where this plant occupied an irrigated area. The farming community stood at risk of losing hundreds of millions of dollars per year owing to reduced plant yields. It was thus necessary that they come up with means to deal with the infestation. In six years since the invasion became a problem, the community spent at least three million dollars in control measures.

This plant displaces native plants when it establishes. As such, farmers end up getting little out of their efforts, with yields decreasing over time. This problem is not only prevalent in Australia but other countries as well. Examples include China, the United States, Indonesia, and Thailand.

Rice-growing countries are significantly affected by the wide distribution of this plant. It reduces the yield by as much as 45% in China. That means that farmers get half or even less of their expected yields, thus affecting their livelihoods. Wheat, lettuce, and sweet potato farms are also at risk, as are others.

In 1999, North Carolina reported an invasion of more than four thousand hectares dedicated to crop farming. Not only did this affect the yields from the farms, but it also threatened the livelihoods of farmers.

Another problem comes in when this weed occupies waterways, thus impeding access to water sources. Such was the case in Liverpool city before 2000 where the council spent thousands of dollars per year in maintaining pest-free rivers. Through the removal of this weed, people were able to navigate the waters while having a clear view of what lay ahead.

The Mississippi River has also had its share of infestations. The government has thus spent a lot of money in controlling this weed. It gets worse when the weed affects hydroelectric plants as this limits power output while putting people’s lives at risk. An excellent example of such an affected region would be China.

Fishers have had to bear with reduced fish numbers in habitats, owing to the unsuitable conditions. What’s more, they cannot access the water sources due to the dense impenetrable masses that block the waterways. Casting nets in such infested waters is not practical as they could get entangled and destroyed in the masses.

Management of alligator weed

The growth and spread of alligator weed is a significant concern in introduced regions. For this reason, people have to ensure that they contain and eradicate this weed in the most effective means possible. In this regard, there are three approaches. In the first one, you rely on immediate eradication, which is possible in new infestations.

The second is suppression that leads to eradication. This technique works for slightly larger infestations that require containing before eradication is possible. The last approach is ongoing suppression, which works for dense stands where eradication may not be possible.

When choosing an approach, you should consider how big the infestation is and how far the plants extend into the ground. In this way, you can tell what works and what does not. An example would be where the infestation is large, and the control costs are over your budget.

In this case, it would be best to suppress the outbreak as you seek means to eradicate it. Here, you would work on reducing the biomass, which would help you reduce the costs of the operation while containing the infestation. While this approach could take years, it might be the only option available to you, based on the site conditions.

The most important thing is to contain the infestation and keep it from spreading. You can then work on dealing with the plants. Failure to contain the outbreak will lead to further spread, and this will escalate the costs and time taken to deal with the weeds. It could also make it impossible for you to manage the infestation.


Prevention is an integral part of managing the spread of alligator weed. Here are some of the critical measures that you can take in this regard:

Reporting new infestations

When you come across an outbreak, the first thing you should do is to alert the relevant local authority. In this way, they can guide you on what you should do about it. In some areas, you may find that dealing with the weed by yourself is against the law. Start by consulting whoever is in charge; else, you could do something that would only fuel the infestation.

From here, you can map out the infested area. That means you should have a sketch of what areas have dense infestations and where there are isolated plants in play. As you map the area, put some markers on the land to show the extent of the infestation. You can spray the land, use pegs, add coordinates, or any other means you deem to be the most effective.

You must contain the area to ensure that activities do not spread the weeds further. That includes putting up signs on the same, informing land users of the infestation, and moving activities away from the area. If you have animals grazing in the area, you have to keep them from the outbreak. Do not attempt to cut or mow the weeds or other plants in the segmented areas as this could spread fragments.

Fences also help in keeping people and animals away from the area by denying them access. It helps to survey the outlying areas to figure out what could have caused the infestation. It could be that your neighbor is growing alligator weed on their farm. If this is the case, nothing you do on your land will keep the infestation at bay, as the source is very much alive.

Assessing outbreaks

It is always best to get a clear idea of how big an infestation is, as this will help you suppress or eradicate it as soon as possible. Start by getting a picture of how many plants are on the land and how far their root systems extend. You can do this by digging along a plant’s roots to see how far it goes.

In some cases, you may find that you can eradicate all the existing plants. For example, if the plants are few and scattered, you can get rid of them by digging them out. That applies to areas that are no more than five square meters. For infestations that are up to ten square meters, you can use mechanical excavation to remove the plants. Note that the root systems should not exceed thirty centimeters in depth for this to be practical.

For scattered plants growing in water, you can work on removing the infestation by starting at the top and heading downstream. This method will work for new outbreaks. Where the roots are more than a meter deep, you should work on suppressing the plants as you move towards eradication. This approach is also applicable for infestations that are bigger than ten square meters, or the roots are more in-depth than thirty centimeters.

Eradication approaches work as follows:

Immediate eradication

This approach works best when the infestations are new, small, and yet to establish in the habitat. It also works on isolated outbreaks. Here, you can use chemicals to kill what exists above the ground or water surface coupled with the manual pulling of the underground masses. This approach takes up a lot of time and labor, as caution is necessary when pulling out the weeds. However, failure to carry it out in the early stages brings about added costs in the future. It is thus the best means to deal with small outbreaks.

You should note that this weed’s roots remain viable in suitable conditions. As such, if you pull out the weeds and leave some fragments in the ground, you will encourage new growths. Many methods can work for immediate eradication, and the choice largely depends on the site characteristics. In most cases, people rely on physical removal for small weeds. Excavation can work, but the best way to go about this would be to dig out the plants.

Using physical control methods on their own will not give you the best results. As such, having chemical control means as part of the integration is of the essence. Re-growths are likely to occur after initial treatments, and you will need to keep monitoring the site for the same. You can consider the site free of this weed if five years go by without any outbreaks. Even after this, it is still necessary that you keep an eye on the previously infested site and restore it to its intended use. There have been cases where re-growths have occurred after a decade since the last sighting.

Suppression followed by eradication

In some cases, eradication cannot take place immediately owing to site characteristics, the cost of the project, and other such factors. Here, it would be best to reduce the extent of the infestation, both on the ground and below. In this way, you can attack the plant’s food reserves, leaving the plant starved of nutrients. The masses thus reduce their growth rate and eventually start to die off over time.

It would help if you were consistent with the control measures. If you take a break, the weeds will bounce back and can even be more aggressive than they were in the beginning. Keeping up with the depletion for at least six years will reduce the infestation to a level where immediate eradication is a possibility. You can then work on removing what exists above and below the ground or water surface.

Continuous Suppression

The above approaches work for small to slightly large infestations. In places where the dense masses have established over a wide area, eradication might not be possible. In this case, it would be best to work on depleting the plant’s food reserves over a long time. You can also use bio-control agents which can feed on the plants, keeping them at a given level. Here, the main aim is to keep the weeds at manageable levels and to prevent them from spreading to other places.

Containing infestations

You may have noticed that a lot of emphasis lies on containing outbreaks such that they cannot spread to other areas. In this regard, you need to use physical measures, hygiene practices as well as quarantines to keep the weeds in one place. Here’s how:


Suppose someone has a bad case of the flu, and the doctors cannot quite figure out what is the cause of the strain. What do they do? Do they let this patient walk out of the hospital and pass on this disease? No, they keep the patient under observation where they are sure that other people cannot catch the flu. That is the case with invasive species. The fewer control measures you have in place, the more likely it is that they will spread to other lands. As such, the moment you come across an outbreak, you should start thinking of containing it.

Why is quarantining necessary? Activities taking place near or in an infestation could lead to the spread of fragments over a wider area. An excellent example of this would be the use of boats in infested waters. The boat can pick up fragments which it can pass to other parts of the water body. These fragments could also get to other water sources if the boat enters these waters without getting washed.

Grazing is another common means of fragment dispersal, as is mowing and slashing. Any activity that takes place in the infestation can spread the fragments, including control measures. As such, quarantines are necessary before, during, and after the application of any control method.

Start by mapping the infested areas and putting up marks indicating the extent of the infestation. Having signage on the same will significantly aid in spreading the word. Suppose you are not the only one using the land, ensure that other users are aware of the outbreak and keep them at bay. Animals and humans should remain out of the confined area, and in some cases, fences may be necessary. Always consult the relevant local authority when undertaking such a measure. They can provide you with guidelines on how to go about this to ensure that you do it right.

Hygiene Practices

Now that you have barriers in place, you have to pay attention to the hygiene practices in play. For example, if you use a boat to access the infested area to apply chemicals, you have to clean it. Doing this ensures that the boat will not pass fragments to other areas. All machinery used in the infested area has to undergo cleaning and inspection before and after use.

You might think that prior cleaning is not necessary, but this could not be further from the truth. The machinery could have fragments from other invasive species that you would introduce to your land during control measures.

You can consult the local relevant authority as to which hygiene measures you need to have in place to prevent accidental spread. In this way, you can have some protocols on how to go about containing the infestation. Where such measures are not available, you can use the following:

Suitable Practices

Whoever is in charge of undertaking the control work must consult the relevant local authority. In this way, your work will be in line with the law, and you can avoid complications down the road. Everyone on the site must have a clear understanding of their role in the matter. Those not involved should stay away as their presence only adds to the risk of further spread. Signposts should be in place, displaying the presence of the weed and warning people to keep away from the site.

In some cases, it may be best to start by treating the infestation with chemicals before you begin any control measures. However, it is best to check with the relevant authority in charge before commencing such work. Clean and move any vehicles and machinery on-site to ensure that they do not contribute to the further spread of the weed. Leave the number of machines and vehicles that you will need for the entirety of the project.

Any soil that you extract from the site must undergo inspection to ascertain that no fragments remain in it. Where there is contamination, you should move the soil to a secure disposal site. Discuss with the relevant local authority as to which disposal site would be best for this purpose.

Moving the soil can be a danger to un-infested areas, and you must thus do so with caution. For one, you should cover the trucks moving the soil to ensure that winds do not blow it off the vehicles. Also, it would help if you did not overfill the trucks as this could lead to spilling of contents on the way to the disposal site. As the vehicles leave the site, you must inspect and clean them.

Once you have completed the control work, you should wash all the equipment and cars involved in the process. Where you come across any fragments, ensure that you move these to the designated disposal site. You should have people from the local authority present to oversee this work to ensure that you follow through with the guidelines. It will also ensure that people in your team do not breach the terms of the protocols.

Note that you cannot start working on a weed removal project before obtaining permits from the local authority. To do this, you will need a plan where you will outline the measures you have in place to ensure that you do not spread the alligator weed.


There have been many mentions touching on the need for cleaning vehicles and machinery used on the site. You should thus set up a cleaning station on a hard and well-drained surface with adequate screening. Have measures in place to ensure that this site remains screened to avoid spreading the fragments. Also, it would help if you mapped out this area in your sketch as it could be a possible source for future outbreaks.

You can use a spray unit or water tanker to clean the machinery and vehicles at high pressure. Note that you will need a lot of water volume to wash the cars and machines adequately.

How should you go about washing everything down? This weed often sticks to mud that is present in the underside of machinery and vehicles. It would help if you thus focused the water pressure on this part. Where guidelines on the same are not available in your locality, you can use the following:

Start by stabilizing the machine or car such that it will not move on account of the high water pressure. Ensure that the engine is off and that the brakes are in place before securing all implements that need cleaning. The cleaning site should be free of obstructions as these could lead to accidents in the workplace. Also, remove any guards on the machines and clean under them. Failure to do this could impede the thorough cleaning of the car.

Work on the storage compartments, too, as well as other places that you could miss during the washdown procedure. Direct the water pressure onto the underside and other parts of the machine and replace all the implements. You can now inspect the area in search of any plant fragments which you should dispose of as needed.

Washing down of machines should take place before and after control measures. You may feel tempted to use a machine as it is, but you should not. For one, it could have fragments of other invasive species that you could introduce to your land. Secondly, if the machine is dirty, the mud will get hard, and this will make the cleaning process later on quite hard.

Also, you should inspect a machine before using it. This process will give you an idea of how intensive the cleaning process needs to be. The machine may have openings that allow fragments to get into parts not mentioned in the cleaning process. You can thus use this knowledge in determining how you will clean the machine.

Using Barriers

Where can you use barriers? On land, fences act as a means to keep animals and humans away from the infested site. You might have to use an electric fence to give animals a shock each time they attempt to access the area. In aquatic and semi-aquatic environments, you can use fences, booms, and screens as follows:


These barriers work in catching fragments that could spread to other parts of the water body. In so doing, they prevent new growths of this weed downstream. You can rely on these barriers where control measures are in place, as the latter will lead to fragmentation. Also, even when no control methods are present, alligator weeds often fragment to pave the way for new plants. As such, having barriers in place will contain their growth in one area.

You can use booms in two ways. They can be in place as you employ control measures such as chemical applications. You can also rely on them where you are working on suppression. The material of choice has to be strong to withstand waves and other forces in the water. Note that a boom cannot be in place devoid of control measures. Alligator weeds have strong stems that can move over the boom and spread to other parts of the habitat. There are numerous types of booms in the market, and you should thus choose what works best for your site characteristics.

Fences and screens

These work in keeping alligator weed from spreading in semi-aquatic environments. Such habitats include irrigation drains, road culverts, and other such places where this weed can establish with ease. Where water is likely to flow near an infested area, having a fence is of the essence as this will reduce the likelihood of the spread. You can use gauge mesh, bird wire, cloth, and other materials for this purpose.

Note that alligator weeds caught by fences can root and thus climb over the barriers. You, therefore, have to keep checking the fences for such new growths. The barriers can also move in the presence of heavy rains, and you should often maintain them to keep them in place.

Control alligator weed

Preventative measures will only aid in containing the weeds, but they cannot eradicate them. To get rid of the weeds, you need to use control measures, as shown below:

Physical Means

You can rely on physical control when dealing with small or emerging infestations. You could also use them when working on isolated stands that are away from dense masses. Note that these means will only work when the detection of the weeds takes place at an early stage. You must remove all materials above and below the ground or water surface. When doing so, you are likely to break the plants apart, and you thus need barriers to prevent the spread of the same. Ensure that you pick up all the plant materials and dispose of them in a recommended manner.

Excavation is one such means upon which you can rely as it is quite effective on small stands. However, its invasive and aggressive nature calls for strict monitoring and subsequent treatments. It helps to note that manual and mechanical means should only come into play for small stands where complete eradication is possible.

What are the risks involved? As you pull or excavate the plant materials, you will fragment the plants. Machinery can pick up these pieces and move them to other places where they can establish. It is thus essential that you wash all machinery involved in the handling of alligator weeds. Where you intend to dispose of the contaminated soil, you must follow the recommended disposal procedures.

Before you work on any infestation, you must treat the herbs with herbicide. Not only does this reduce the bulk of the stands, but it also reduces the viability of the fragments. Herbicides also give you better access to the stands, enabling you to deal with the plants devoid of obstructions. You should use the chemicals around the quarantined area to create a buffer area.

How should you remove the weeds? In this regard, you have two options. You can manually dig out the weeds or rely on mechanical excavation as follows:

Manual Digging

This technique works for terrestrial and semi-aquatic stands that measure five square meters or less. It can also work for aquatic habitats where you have the necessary expertise on precautions while working in water. Where the infestation is more established, you can start by excavating the plants. You can later use physical removal to work on the now dislodged plants. This process also works on stands that have been under suppression for a while. It targets the entire plant from the roots to the shoots, ensuring that nothing remains behind where precautions are in place.

physical invasive plant removal

Physical invasive plant removal is labor-intensive

You can achieve eradication with this method if you follow the guidelines given and follow up with monitoring. Here is how you can attack weeds in different habitats:

On Land

The soil conditions greatly influence how successful the eradication process will be. Where the soils are hard, dry, and compact, you will face difficulty in digging out the plants. Luckily, most weeds grow in moist and soft soils. Start by spraying the area with herbicide and waiting for the recommended time. You can then remove the dead plants to pave the way for manual means. Ensure that you properly dispose of these plant materials. You can now mark the areas where you will commence the digging to make following up an easy task.

You can use several tools to dig out the plants, including but not limited to garden forks and crowbars. Avoid any device that can cut the roots as this will make accessing the underground systems hard. Such devices include spades and shovels. Dig into the soil and loosen the ground under the plant before lifting the plant and soil out of the ground.

Place the dug-up materials on a tarp and break up the soil clogs by hand as you feel for the root fragments. Break up the clogs such that you can tell the alligator weeds apart from other fragments. You can recognize them based on their white centers and brownish skins. If you cannot tell them apart from other fragments, dispose of everything to be on the safe side.

Follow the root system until you get to the end. Then dig a few more centimeters downward to ensure there are no more alligator weed roots present in the ground. Leave the soil on the tarp where it will not experience any disturbance. Alternatively, you can bag the soil and the plants and dispose of them immediately. Fill the empty hole with sand, as this will make it easier for you to deal with any new growths.

As you leave the site, ensure that you inspect your clothes, shoes, and tools for the presence of any root fragments. You can then return to the site after two weeks to sweep the surface over with a broom. However, you should only conduct the sweeping if the ground is dry. This sweeping enables you to catch any new growths before they can establish. Monitoring will be necessary every four weeks or so. If you left the soil on the tarp, you should sieve it to check for any new fragments. Where none are present, you can return it to the site and keep checking for any new plants.

When the conditions are dry, new growths may not occur, and you may think that you have entirely eradicated the weeds. The best approach is to water the sieved soil and the hole and to check back in a month. In this way, you will catch any spots that you missed in the initial treatment.

In Water

You can remove plants by hand when the infestations are new and yet to develop extensive root systems in the substrates. If this is the case, you can start by hand removal before using chemicals on the infestation. Start by erecting barriers to catch any plant fragments that result from the process. You can then roll up the mats, taking care such that you do not break up the plants. It is a much better approach as compared to cutting up the plants as the latter encourages fragmentation.

Get rid of the rolled-up mat and proceed to apply chemicals to the stems in the water. Wait the recommended time then follow through with pulling out the plants from the substrates. You can do this by feeling for the stems and roots in the substrates. As you do this, break up the mud slowly until you get a good hold of the roots. You can then pull out the plants.

Where the water is shallow, you can start by using a pitchfork which will work on pulling out the stems. You can then reach into the hard substrate and pull the plants out by the roots. Work to get as many root systems out of the water and keep checking the site for any new plants.

Is it worth it? Manual digging is quite labor-intensive, and it takes time to get the hang of it. However, after a while, inspecting the root fragments and removing them in one piece becomes second nature. Plus, it is the best way to deal with an infestation before it becomes too dense to eradicate. Also, you can make the work easier by letting the stems float to the top by loosening the substrate. As long as you have a barrier in place, the stems will not get away.


Excavation aids in the removal of plant materials above and below the ground. In some cases, this method is effective in the removal of root fragments to the point of eradication. It works on both land and water and is best for isolated cases as well as for chemically treated plants. Also, it comes in handy where people wish to create means of access to an infestation.

For this method, you can use excavators and backhoes as well as other such means. These devices aid in shallow excavation, paving the way for eradication or suppression. All machines used on the land should undergo inspection and cleaning before their use. Also, you must consult the relevant authorities as to the need for excavation, and obtain permits on the same. This method is quite intensive, and it is thus essential to have people on the ground to guide the machine operators.

Start by applying chemicals on the infestation as this will reduce the viability of the fragments. Wait for the recommended period before carrying out any work. Dig to a depth of ten centimeters and gauge how far the roots go and how extensive they are. Where the roots are extensive, you can dig further to a depth of twenty centimeters.

Digging further than this is not recommended. You would have to deal with a lot of contaminated soil, which would require treatment and disposal. It would also cause the disturbance to spread over a wide area, which could encourage new growths. If you go about the excavation right, you should end up with a clean area.

Following up on the site conditions will be necessary, and you can do this three weeks after the procedure. It will help you catch any new plants as well as assess the root systems of the deeply-rooted weeds. You can then decide if you will pull them out by hand or use chemicals to control their growth.

All excavated materials should get put in lined trucks and taken to the disposal site. Ensure that you exercise caution during this process, such that you do not end up spilling soil during transportation.

Chemical Means

Using chemicals near or in water requires that you get a permit from the local authority. It would help if you had a plan in which you outline what measures you will take to ensure that you protect the habitat and its users. Extreme caution is of the essence in this case.

All regions have guidelines as to the use of herbicides near and in water. Checking with the local authority for requirements on the same will thus aid you in abiding by the law. When selecting chemicals, ensure that you get those which work for aquatic habitats.

Also, read the label as it will serve as the law regarding the application and protective measures you should have in place. Each time you use a chemical on the land or water, take note of this and keep records on the same. Anyone using the chemicals should have the necessary know-how, else they pose a risk to themselves and other people.

Do herbicides work? For a long time, alligator weed has proven to be resistant to the effects of herbicides. It does so by limiting the translocation of chemicals to the plant parts in the underground. As such, the chemicals do not get to the root systems, and the plants keep thriving. However, some herbicides have proven to be effective in reducing weed infestations. They are metsulfuron-methyl, glyphosate, and dichlobenil.

Metsulfuron-methyl is selective, and it works for plants on land, but you can use it in the water where the local regulations allow for the same. It leads to a slow death of above-ground plant parts and should take about one to two months to show results. It shows a lower re-growth rate when compared to glyphosate. It’s suitable for ongoing suppression as well as suppression in the hope of eradication.

Glyphosate is non-selective, and it works on both land and water. It results in the fast dying back of the above-ground plant parts, but the translocation rate of the compounds is slow. It works for high use public areas as well as aquatic habitats where metsulfuron-methyl is not suitable.

Dichlobenil is a non-selective chemical that works on aquatic weeds. It suppresses shoots in the upper soil layers and delivers results for up to six months. However, after this period, the plants can continue growing, and it thus works best for suppression.

This article will not delve into specific products but will instead act as a guide on chemical means available to you. The best approach is to engage the local authority and follow the chemical control measures in place.

Biological Means

Biological agents will not eradicate an infestation, but rather, they will suppress the growth of weeds. They are best for areas where chemical means will not work owing to the inaccessibility of the weeds or the density of the stands. Find out what biological agents are available in your region and how they could work for the infestation in play. At present, the following options work in Australia as well as other introduced regions across the globe:

The Flea Beetle

Adults and larvae feed on leaves and stems of this weed and pupate in the mature hollows. In so doing, the new adults bore through the stems, thus damaging them. These entry points allow for rot-causing organisms to enter the plants and destroy them. The plants collapse and rot, breaking up in the process. In water, the dense stands sink to the bottom where they continue rotting.

Alligator weeds can grow from the root systems in the bank of the water source. For this reason, you cannot achieve eradication with this species, and it cannot work on terrestrial plants. Also, it will not work in climates that are not warm temperate or subtropical. However, you can rely on it to reduce the size of an infestation as well as suppress it.

Alligator weed moth

This moth works for aquatic habitats where it controls the growth of alligator weeds. It, however, does not work for terrestrial plants. When introduced in a water source, it establishes at a slow rate but can show results in as little as a year. Its larvae form tunnels inside stems, and in so doing, they damage the plant tissues. You can use this moth together with the beetle for the most effective results.

Disposal of alligator weed

You must dispose of the plant materials as well as the contaminated soil in the prescribed manner. Failure to do this increases the chances of new growths, and it puts the habitat at risk of more outbreaks. You must treat the soil and plant materials to kill the viable fragments and dispose of them as recommended. Guidelines for the same are as follows:

Plant Materials


Note that if you need to move the fragments to another site for disposal, you must adhere to hygiene practices as outlined under preventative measures. You should also obtain permits to enable you to move these plants from one place to the other.

Where you hand pull or excavate fragments that are devoid of contaminated soil, you can proceed with drying and incineration. For this, you can use an oven or other such devices with a hard surface. Ensure that you turn the materials to the point that they are dehydrated. If you attempt to burn the plants when wet, you will not succeed in destroying the fleshy parts of the roots and stems.

This method works best when dealing with small infestations where the plant materials are few. You will not need any special equipment for this process save for a hard-surfaced oven. Once you burn the plant materials, you can rest assured that you have properly disposed of the fragments.


Here, you can either boil the plant materials for half an hour or put them in a microwave for at least five minutes. For the latter option, ensure that you use the highest heat. You can then proceed to dry and burn the materials as outlined under incineration. This technique also works for small infestations.


When dealing with large amounts of plant materials, using drying may not be the most practical solution. However, you must be careful when composting; else you might encourage the growth of new plants. Thus, you must adhere to composting guidelines as provided by the local relevant authority.

For one, you must expose the plant materials to temperatures above 55 degrees Celsius. Secondly, the plants should be in the compost pit for at least three days under these temperatures. Where you cannot meet these conditions, the resultant compost should not get reused, and you should dispose of it as recommended.

The composting pit should have impenetrable surfaces to ensure that fragments do not root. Also, you must keep turning the plant materials all the while, as lack of this can encourage new growths.


When using mechanical means, you will contaminate the soil with fragments, and you thus have to figure out a way to treat and dispose of the dirt. In this way, you can reduce the likelihood of an outbreak. Here’s how to go about this:


In this process, you will kill the fragments present in the soil. The method you use will depend on the amount of soil as well as the budget you have set out for this process. Note that all treatment methods carry the risk that the fragments could survive and thus root when re-introduced to the land.


Here, you spread out the contaminated soil and dry it in an open environment. Ensure that you do this on a hard surface to avoid contaminating un-infested sites. Also, you should turn the soil often to ensure that it dries completely. As you do this, feel for fragments and dry and incinerate them before disposing of the soil. It is better to dry the soil in ovens and other such devices where the temperatures are high enough to kill the fragments. Break it up to expose a wider surface area.

This method works for small to moderate amounts of soil, and you can achieve this without using specialized equipment. Ensure that you completely dry out the soil; else, any present moisture will encourage the viability of the fragments.


This method works when dealing with small amounts of soil. You can use pasteurization units or other such devices for this process. Note that this technique might be hard to use owing to the specialization of equipment needed for this.


Where you have carried out excavation, you can use this method to deal with the contaminated soil. However, you should note that for this process to be effective, the soil should comprise a fifth or less of the total plant materials.

Disposal tips

Given that treatment methods do not guarantee the death of fragments, it is best to dispose of the soil. That means that you cannot use the soil in compost or fills, else you risk spreading the weed. Move the treated soil to a burial site. Where you can seal the burial site, the chances of the weed spreading will be minimal. Ensure that you regularly inspect the site to check for any new growths.

Alternatively, you could move the soil to a secure disposal site, such as in a warehouse. You should engage the local relevant authority as they can guide you on the designated places for this. The site should have clear signs, minimized access, and should not be near a water source. It is also best if the site is isolated, as this will reduce the chances of disturbance in the future.

Burial sites work in the disposal of both treated and un-treated plant materials. Ensure that the pit is at least three meters deep to reduce the likelihood of new growths. You should note, though, that these weeds can grow through several meters of soil, more so when the soil is loose. It is thus better to bury treated soil where the chances of new infestations are low. You should also hardpack the soil to make the conditions unsuitable for new growths.

Also, the burial site should not be lower than the water table as this will give the plants access to moisture. Where water is present, any viable fragments are likely to root.


Dealing with alligator weed requires a lot of resources, and it is best to engage local authorities and all land users in this process. It is only this way that you can prevent this weed from spreading and achieve control over time. Remember that the faster you act, the higher your chances of immediate eradication. All the best in your endeavors!