The Tree of Heaven also goes by the name copal tree, varnish tree, China Sumac, and paradise tree, among other names. The naming also depends on the region where it is. For example, in China, people refer to it as the bai chun while in France, it goes by the name faux vernis du Japon.
It has gained a reputation of being highly adaptable to infertile soils and establishing at a fast rate. What’s more, it has a prolific fruiting capacity and germinates with ease, making it a noxious weed in many countries. An excellent example of a region it has invaded is the United States, most notably Hawaii. It has also invaded many states in the South, many of which are under monitoring.
Australia is also dealing with high levels of invasion, and there are measures to curb this plant’s growth. The same goes for South Africa, where it falls under the classification of a category 3 weed. Under this classification, it is up to the farmers to ensure that they contain the infestation to keep it from reaching water sources and other gardens.
Tree of heaven identification
The Tree of Heaven belongs to the genus Ailanthus, which has ten species under its name. Most of its species occur in north Oceania and Asia. In these natural habitats, the plants are not invasive. However, when introduced to other areas, the Altissima has proven to be problematic. Other than the Altissima, people also need to be wary of the tanakai and sutchuensis.
Physical Characteristics
Stem
The Altissima is easy to identify owing to its curving branches, which adorn its stem. The branches are grey with a smooth and glossy finish, punctuated by dots. In old age, the branches have some fissures. Twigs resulting from the same appear velvety, and they bear a striking reddish-brown shade.
In most instances, it grows to heights of 20 to 30 feet. But where the conditions prove to be ideal, the varnish tree could be as tall as 100 feet. The crown can be as wide as eighty feet, with a three-foot diameter trunk to boot.
Its bark is smooth with pale white stripes adding to its beauty. The bark physically changes as the tree ages. At an early stage, the bark features a light brown to a grey hue. As it matures, the bark becomes rough, spotting fissures along the trunk.
The wood from this tree is soft and weak and comes in a light brown tone. It breaks with ease and would therefore not be suitable for hardy furniture.
Leaves
This tree has compound leaves that can measure anything from one to four feet, depending on the prevailing conditions. Each leaf will have ten to forty leaflets, which range from two to seven inches in length. The leaves have dark-green hues with teeth lining the margins. At the bases, you will find lobes, and underneath the leaves are red dots lining their whitish-green undersides.
Flowers and fruits
The flowers are many, unisexual, and small with yellowish-green hues. The male flowers have unpleasant smells. The flowers result in clustered fruits measuring a few inches. For every kilo of fruits, studies show that the varnish tree gives rise to seven thousand seeds on average.
Longevity
This deciduous tree is perennial, but one with a short life. It can live for thirty to fifty years.
If you come across a broad-leaved, woody tree matching these characteristics, you could be dealing with the tree of Heaven.
History of the tree of heaven
This tree is native to some parts of Asia, such as China. It spread to Europe in the eighteenth century, where it established over a large area, raising concerns. At around the same time, it spread to the United States where it naturalized in North America. Some affected areas include Kansas, Texas, Florida, and Massachusetts. In some of these invaded regions, the varnish tree has established so much that it looks like a part of the natural vegetation. Its introduction owed to its ornamental benefits.
Though it is native to Asia, it got introduced to other parts such as India, where active cultivation of the tree took place. Thanks to its ability to withstand harsh growing conditions, it is common along roadsides, plains, and hills. Indians have used it as a means to restore forest cover in deforested regions.
And India is not alone in this, as Iranians have relied on the use of this varnish tree in a bid to increase forest cover. It has been especially the case in dry regions where other trees would not easily establish.
This tree does well in temperate regions and has, therefore, spread to other areas such as Indonesia, Malaysia, and Australia.
The tree of Heaven serves many purposes, among them aesthetic value, soil erosion control, and provision of shelter. It is due to these benefits that the spread of the tree could take place to unaffected regions over time.
Where does tree of heaven grow?
This tree has a preference for warm climates. However, that does not mean that it would not establish in cool temperatures. A good example would be South Africa, where this species has established along roadsides, riverbanks, and forest edges. The climate in this region is cool, yet the tree has not had trouble thriving.
Europe is another region where the varnish tree has spread fast, even though the climatic conditions are not ideal. Here, it is common in disturbed areas such as roads, old fields, and riparian forests.
In the United States, this tree is common in wooded areas, as long as there is a presence of moisture.
How does tree of heaven grow?
This tree gives rise to unisexual flowers that occur on different trees. Flowering starts as from May to August, leading to the formation of fruits, which form clusters as from September. As of October, the fruits are mature, and seed dispersal begins and continues through to the next spring. One varnish tree can release as many as one million seeds into the environment through wind dispersal.
Vegetative propagation also takes place, and where this is the case, early flowering is common. This tree has a high tolerance of high temperatures as it can control transpiration rates. As such, it can establish even in drought-stricken areas. Plus, it has porous wood, which allows for a fast transfer of water from the root system to the leaves. In this way, it can survive harsh weather conditions.
Varnish tree germination
This tree does best in temperate to sub-tropical weather conditions. But where there is heavy rainfall, seedlings are likely not to survive. It will thrive in regions where the annual precipitation ranges from 400-1400 millimeters per annum. It can withstand a few dry months in a year, with a maximum of eight.
Temperatures should range from seven to eighteen degrees Celsius in a year. Studies show that the varnish tree can survive temperatures below zero up to -35 degrees Celsius. Also, frost will not kill the tree.
As for altitudes, the tree of Heaven will grow in regions ranging from 650-8.000 feet above the sea level. An excellent example, in this case, would be in the Himalayas region where the trees grow in the 5.000-6.000 ft zone.
The distribution of the tree of Heaven will largely depend on climate and the soil conditions. For example, in central Europe, weather conditions play a vital role in the establishment or lack thereof of the tree. But in Mediterranean regions, soil fertility takes the day. This tree does best in loose and porous soils, but it can adapt to other soil types, including clay soils. It can even grow on barren rocks where the rainfall received per annum proves to be sufficient.
Can you use tree of heaven?
This tree has been in use for a long time, owing to its many benefits. For one, it provides shade in an area. Two, it aids in preventing soil erosion, thus protecting the upper layers of the soil. Three, it adds to forest cover and thus improves the state of the atmosphere. For this reason, it comes in handy when people are working to reclaim land.
The tree of Heaven is also a source of wood which works for making furniture, fibers, packaging, and paper pulp. It is light and easy to dry. It helps that the wood is resistant to decay as this adds to its longevity. In some countries, this varnish tree is a source of fuel.
The leaves are also essential as they have proven to be a source of food for silkworms. The roots work for medicinal uses as they alleviate the symptoms of epilepsy and asthma. The seeds are rich in fatty oils and proteins.
The beauty of the tree has earned it the status of being ornamental. Some people grow it for its aesthetic value.
Tree of heaven threats
How does this plant spread, and how can you stop it from doing so? Also, does it have any effect on the environment? Here is what you need to know:
Dispersal
The tree of Heaven has three primary means of dispersal as shown:
Natural
The seeds are small, and this aids in dispersal by wind. For trees growing along water sources, dispersal by water channels also takes place. Where this species establishes in an area with human traffic, dispersal by animals and humans is possible.
Intentional
The introduction of the varnish tree in many regions outside Asia took place through deliberate cultivation. People lauded the tree for its beauty and ability to control soil erosion. Thus, they actively planted it and still do. Some people also look to it as a source of shade and timber.
Accidental
Where the seeds make their way to pasture fields or other such areas, movement by animals and humans could lead to their spread. Using infested manure could also aid in the distribution of this species. Escapes of the seeds from gardens and confined areas are also possible, leading to their spread. There have also been instances where disturbance of infested areas led to new growths.
Impact
What effect has this tree had on areas which it has invaded?
Environmental
Where the varnish tree establishes, it forms a monoculture, more so along water sources. As this happens, it pushes out native vegetation that cannot compete with the trees. Seedlings grow quite fast at a rate of up to fifteen feet per year. And they compete with native species for light, space, and nutrients.
As they grow, their leaves and barks release toxins into the soil, which get in the way of native species’ growth. When these toxins accumulate in the ground, other native species cannot take root. The biodiversity of an area thus changes over time.
Economic
This tree can establish along sewer lines as well as buildings. When this happens, the roots of the tree can damage infrastructure by affecting the foundations. It can thus lead to considerable economic losses.
Additionally, where this tree releases toxins into the ground, it can inhibit the growth of crops. Farmers would thus face a reduction in land productivity.
Controlling this tree is quite complicated, and it calls for a lot of capital investment, which negatively impacts the economy.
Managing the tree of heaven
Under management, we will cover both prevention and control. Prevention works to stop the spread of seeds and thus keeps healthy sites safe from this species. Control works in dealing with the tree where it has established. The methods work as follows:
Prevention
With the tree of Heaven, it is best to keep this species from establishing as prevention is easier and less costly than control. If an infestation occurs in one area, people should direct their efforts to ensure that seeds do not spread to neighboring regions.
Where the infestation is on a small scale, treatments should take place to ensure that no more trees can grow. Where the trees have matured and have not caused ecological changes, measures should be in place to prevent the spread of seeds. In this way, new species will not grow from the female trees. But if the trees have caused changes in the biodiversity in an area, there should be efforts to remove or control the trees.
Given that this varnish tree is quite big, control measures work best when they frustrate the root system. When the roots are under threat, the tree cannot produce as many seeds as it would under different conditions. An excellent way to deal with an infestation would be to attack the tree during summer when food reserves are low.
At this point, the tree is quite weak and can thus not produce seeds at an optimum. It would be necessary to keep attacking the tree and the root system to ensure that it does not regain productivity.
Once you have controlled the tree, you can work on introducing other species to the vacant land. It would be best to bring in tall native species that would shade out the tree of Heaven. The latter is intolerant to shaded conditions, but to an extent. It would, therefore, be necessary to bring in other control measures.
Controlling this tree will not only set you back regarding capital, but it also calls for an investment in time. Depending on how extensive the invasion is, you could spend anything between one and five years dealing with the infestation. During this time, you would be planning and implementing management strategies. It helps to have the support of a relevant local authority. Other than that, here are some considerations you would need to take:
Points to Note
Having a healthy plant community on-site reduces the chances of an infestation. The tree of Heaven is likely to establish in open ground, before spreading to occupied regions. It is thus essential to cover bare soil with desirable species. Also, where an infestation was once present, it is best to avoid disturbance in the area as this could encourage regeneration of the species.
Monitoring is of the essence when it comes to fighting this tree’s spread. You should thus get involved in the community where you can get regular updates as to the sightings of the varnish tree. Where you come across an infestation in your land, map out the area, and keep a record of this. The same goes for any infestations in your neighborhood.
Having this information will keep you in the know if the species starts to spread. You can always refer to your records and see how fast the spread is taking place and if the preventative measures in place are working.
Integrating different methods of control is the easiest way to deal with this tree. Though some people have reported success by using one approach, the best results come from those who have used two or more. There is power in numbers, and having more methods on your side guarantees you a high success rate.
Dealing with the tree takes time. After conducting initial treatments on infestations, you will need to conduct a follow-up. It will help you gauge how well the treatments have worked, and if there is a need to use more treatments on the land. It is essential to have records on the same as you go about monitoring previously invaded lands.
Tree of heaven control
Before choosing what control measure you will implement in your land, there are some factors you need to consider. One, how big is the infestation? Two, how do you use the land at present? Do you plan to change the use, and if so, how will the control measure affect this purpose? Three, is the site accessible? Are there native species in the land which could get affected by the method of choice? Four, how soon do you wish to get this over and done with? Five, how much will the process cost? And the most crucial factor is six, will the method work?
In most cases, especially where the degree of infestation is high, using more than one control method will be ideal. Below are the current control methods:
Physical control
Using physical means to control this species is possible if you wish to suppress the growth of the varnish tree. However, you should note that manual methods, on their own, are not highly effective. When cut, the trees re-sprout with ease and their root systems spread over a wide area, leading to the growth of new stems. Thus, in the past, where you had a few seedlings and trees in an area, the number grows. As such, you end up requiring more cutting and more follow-ups, which adds to the work cut out for you.
Physical means will vary based on the growth stage of the trees. When the trees are young, you can cut them down before they shade out native species. Also, you could wait till summer when the root reserves are low before cutting the trees. They would have a hard time re-sprouting as they would lack the resources to do so. However, they would grow again over time and fast.
The other option would be to cut the varnish tree and wait for re-sprouts, which you can then treat with herbicides. This process has proven to work as the chemicals work in inhibiting further growth. And when you have succeeded in eliminating the trees, you can work on restoring native species which can shade out any re-sprouts. Do any of these ideas appeal to you? Well, here is more information on the same:
Hand Pulling
When the seedlings are young, their root systems are not extensive, and pulling the plants out of the ground is thus easy. However, you should note that this will depend on the state of the soil. You have a higher chance of success if you pull them out when the soil is moist. In this way, you can get the entire root and avoid leaving any fragments in the ground. If the soil feels dry, irrigation could ease this task.
You can tell the seedlings apart from root sprouts based on their appearance. Seedlings have slender stems with trifoliate leaflets. If you pull them out when young, they should have their cotyledons intact.
Extraction
If the trees are past the seedling stage and now fall under the classification of young trees, more force is necessary. Here, you can rely on the mechanical extraction of the root systems. Note, though, that you cannot use this method for mature trees as it would be hard to get the whole root system. It would also not be a practical way to deal with mature, established trees. Can you imagine how much effort and time you would need to deal with a dense infestation of mature trees?
Physical invasive plant removal is labor-intensive
Cutting
Let us suppose you have large trees growing in your outdoors, and you can, therefore, not get a good hold of the root systems. What do you do in this circumstance? Well, all you need to do is to attack the trees at the ground level. That means you can mow them down or cut them using another means. After a while, the varnish tree will re-sprout, but the emerging wood will be soft and easy to cut down. In this way, you can keep attacking the re-sprouts each time they establish as this will diminish the root reserves.
The root system will thus not spread as it would, and over time, you should notice a reduction in the re-sprouts. You should note that this method only works if you are consistent with the timings. If you let the re-sprouts grow too tall, you will have a hard time containing their spread as the root system will establish further. Also, the wood will get harder to cut over time.
An excellent way to attack the tree of heaven would be to cut it at the ground level and wait for re-sprouts. At this time, you can use chemical treatments on the stem as this would inhibit the growth of more sprouts. After a few follow-up treatments, you would be in a position to start reclaiming your land.
Can you use fire?
Using fire as a means to control this varnish tree is not advisable as it would trigger root and stump sprouts. The tree of heaven would work to spread in response to the fire, which would get in the way of your control efforts. However, you can rely on scorching the plants one by one. But this would also require that you treat the emerging sprouts and conduct periodic follow-ups on the site. It is a lot of work with few or no returns. It is thus advisable to avoid using fire as a control measure.
Physical controls as per habitat
Along roads, fences, and forests
In this case, it would be best to start by cutting off the larger part of the tree of heaven to the ground level. You can use power saws, machetes, and loppers for this, depending on the extent of the infestation. Where possible, the cutting should take place towards the end of spring or the start of summer. Follow up with regular cutting to deal with the re-sprouts. You can achieve better results faster if you couple the mowing with chemical treatments.
Pasturelands, croplands, and rangelands
Here, you need to get rid of the trees to create space for other uses such as cattle farming and crop cultivation. Therefore, it is best to nip the trees in the bud at a young stage. You can achieve this by pulling out seedlings as well as extracting young trees. Using a recommended chemical for treatments is necessary to deal with the sprouts. Hand pulling alone will not cut it if you intend to use the space for farming.
These techniques also work for riparian lands where there is a need to protect water sources.
Fields and Openings
In this case, the infestation is likely to be dense, and where left alone, it can spread even further. For this reason, you cannot solely rely on physical means, and there is a need for integration.
Natural Areas
Here, you need to hand pull the weeds while avoiding disturbance on the site. Water the soil where the conditions are dry, as this will help you get hold of the entire root. Where the trees are older, you will need to follow up with chemical treatments as hand pulling will not suffice.
It is clear that the success of the methods heavily relies on the extent of the infestation. Where the trees are large and established, you will need to follow up with subsequent chemical applications. For small invasions, you can rely on hand pulling. The method of choice should also be in line with the regulations in the area.
Cultural control
Cultural means are all about detecting infestations before they spread and preventing the establishment of the same. The success of these methods heavily relies on the involvement of the community and relevant authorities. It covers the identification of the tree of heaven, containment of infestations, and disseminating information on the same. The aim is to prevent the dispersal of seeds as this would lead to more outbreaks in an area. Here is how it works as per the habitat:
Along roads, fences, and forests
People working around these areas need to know how to identify the tree of Heaven. In this way, they can report to the relevant authorities in case of any sightings. Controlling infestations and reducing disturbance would, therefore, be an easy task.
Pasturelands, croplands, and rangelands
Local authorities should work with farmers to help them understand the best control measures in line with the use of the land. Any infestations should get dealt with immediately, and subsequent monitoring procedures should follow. Disposal of the trees is of the essence, and this should take place through burning or bagging in landfills.
Where there are infestations, there should be signs showing the same as this would prevent people from accessing the areas. There should also be adequate information on how to identify the tree of heaven along these corridors.
Fields and Openings
In these areas, there is likely to be construction or logging activities taking place. Before any of these can commence, monitoring of the site should take place to identify any trees. Where there is an infestation, control measures should come in to eradicate the trees. Failure to do this will expose other areas to outbreaks resulting from activities in the site.
Natural Areas
There should be signs indicating the presence of an infestation in natural areas so that people can be cautious as to their activities. The signs should get into how one can identify and report any sightings of the tree of heaven. Hikers, bikers, and other outdoor enthusiasts would thus have the tools necessary in fighting the spread of the tree of Heaven.
Biological control
Biological means often have the least impact on the environment and are thus the most preferred. When dealing with the tree of Heaven, you will not have much luck with biological control. It owes to the lack of approved biological control agents as they are still under research. The release of these agents will go a long way in eradicating this tree, more so in organic farms.
However, you can rely on grazing animals on the seedlings and young trees. Most grazers will avoid the foliage on this tree as it is unpalatable. But during some seasons, they will feed on it owing to the lack of choices, especially where there is a change in the eco-system. The good thing is that the foliage does not have any adverse effects on animals.
Goats can feed on the bark as well as the leaves of the varnish tree. Deer can feed on foliage in the hot months. Cattle and sheep will also occasionally feed on the leaves.
Where the animals have no alternative and have consumed all the leaves within reach, they will feed on suckers and sprouts. Grazing, in itself, will not eliminate the trees. However, it will suppress their growth, and if you couple it with herbicide applications, it will prove to be effective.
Management as per habitat
For all habitats, the trick lies in allowing goats to graze in the infested area to suppress the trees heavily. You can then follow up with applying chemicals to inhibit the growth of sprouts.
Chemical control
All through the control methods, there has been an emphasis on integrating other measures with chemical treatments. And there is a reason for this – chemical control is the most effective means of dealing with this tree. Not only will it kill the root of the tree of heaven, but it will also inhibit the growth of root suckers and sprouts.
The good thing with herbicides is that they provide you with a wide array of means to attack the tree of heaven. You can apply the chemical on the leaves, cut stems and stumps, the base, or inject it into the trunk. Whatever method you choose should work on controlling the root system to kill the varnish tree completely. Sure, attacking the plant from the leaves will suppress and inhibit growth. But with the root system intact, new suckers will form, and so will sprouts. And you will start all over again.
Thus, as you choose a herbicide, ensure that it can work on the root system. You can also choose to attack the plant from more than one surface. All chemicals that you use should be safe for use near native species, where any are available. You should also consider the long-term effects of the chemicals, especially for arable land. The time taken to see the impact of the application is also essential, as is the total time used in treatments.
One last thing to note is that you should get a chemical permitted for use in your locality. Where you are unsure of the legality of a product, refer to the relevant authority. And always use the chemical as stated by the manufacturer, for best results, and safety.
Let us now delve into the various chemical control methods in place at present and how they work:
Foliar Application
This method works best for young trees as well as trees that are yet to reach great heights. It would be difficult to access the leaves of full-grown trees. For this application, you will need a backpack sprayer for small infestations. Where you are dealing with a significant infestation, you can rely on a truck-mounted sprayer as this will ease the work cut out for you.
You need to get all the shoots and green leaves wet, without missing any patches. The herbicide of your choice should be one that can get absorbed through the leaves, and you should thus check for this. Also, avoid using the chemicals on native species as this can kill desirable vegetation.
Basal Bark Application
In this method, you do not need to cut the trees, and it thus does away with the need for physical means. This application is most effective when conducted when the leaves are full and yet to change their color in fall. Note that this method is labor-intensive, and it would thus be best for small infestations with tree diameters between four and eight inches.
For tree diameters that are less than six inches, you should cover the base of the tree with a twelve-inch band. Anything bigger than this will require a twenty-four-inch band. Having some dye in the solution will be useful in determining the coverage of the chemical. However, the coverage and the application instructions will depend on the label.
A backpack sprayer would be helpful in this quest. It is important to note, though, that you should wet the trunk and not allow runoff, as this could affect the soil. Follow-up treatments are necessary to deal with any new sprouts.
IPT Cut Stump Application
It could be that mechanical methods will not work, for one reason or the other. You could also find that foliar application poses a threat to native species in the land. In this case, the cut stump treatment would be the best option. Here, you cut a tree as close to the ground as you can before applying a chemical on the cut stump. You need to be careful during the application such that the herbicide does not come into contact with non-target species.
Note that plants seal cut areas fast and you should be fast with the chemical application. Else, the herbicide will not get absorbed. Ideally, you should follow up with chemical application within five minutes of cutting the tree of heaven.
Follow-up treatments may be necessary in the future, depending on the effectiveness of the application.
Girdling
Where the trees have large diameters, this would be an ideal option. That is, anything above eight inches, as the bark will be thick. Make two horizontal cuts on the trees around the trunk, with a distance of two to four inches between the grooves. Within five minutes of the cutting, apply a herbicide to the grooves. Failure to do this will lead to the production of stem and root sprouts.
This method works best in summer as the trees will be in active growth. After application, you can leave the varnish tree in place as working on it can lead to sprouts.
Conclusion
There are many means which you can use to control the growth of the tree of Heaven. Your choice will depend on the site conditions as well as the level of infestation, among other factors. Where possible, it would be best to integrate the methods as this has proven to be the most effective control method.
Once the trees are out of the way, you can work on restoring the land by using desirable vegetation in once infested areas. Monitoring will also be essential in dealing with sprouts as they occur.
