Purple loosestrife is known by the scientific name Lythrum salicaria. It is a wetland plant and does well near water. Other common names of the invasive plant are spiked loosestrife, beautiful killer, salicare, blooming sally, flowering sally, and purple Lythrum. This plant is a known invasive, and in this article we will talk about how to get rid of purple loosestrife in your yard.
The origin of purple loosestrife is Europe and Asia. It was brought to North America in the 1800s. The plant was most likely transported from Europe through sailing ships as it was carried together with soil which was used to steady the ship.
The plant is noxious and can block water channels. In some instances, it can be found in planting seeds. Therefore, you should buy certified seeds and always verify them. Once established, it can take several years to get rid of purple loosestrife in your yard or farm.
How to Identify Purple Loosestrife
Purple loosestrife grows to an average of 5 feet. The perennial herb blossoms between July and August. It produces purple flowers, thus the name purple loosestrife. The flowers are held by spiky sepals found at the tip of the branches, which contain some spikes.
The leaves are arranged in a whorled or opposite pattern and they are smooth. They are rounded or heart-shaped. The leaves are around 2-3 inches long.
Each plant can produce a batch of up to 50 stems. The stems are square and ridged. The roots are fibrous and extensive making the plant difficult to control. Each plant can produce as many as 2 million seeds in a year. The seeds are held by a small fruit; about 0.2 inch in length. This makes it difficult to get rid of purple loosestrife completely.
Purple loosestrife petals are reddish-purple in color. They have around 5 petals clustered together. Some flowers have 6 petals but they are rare. The flowers are pollinated through cross-pollination or self-pollination.
Some look-alike plants are the fireweed, swamp loosestrife, winged loosestrife, and blue vervain. You should differentiate these plants from the invasive flowering sally.
Purple loosestrife flowers
Natural Habitat
The plant is common in wetlands and along water bodies. It can easily invade water channels causing a blockage. Its extensive roots and stem degrade the habitat for animals and other plants. The plant does well under exposure to the sun but can also grow under the shade. The plant can also withstand dry soil to some extent. Flowering sally is found in most parts of the world: Southern Australia, Asia, North-Western Africa, and North America.
Reports of purple loosestrife in the US
Medicinal and Food Value of Purple Loosestrife
The plant contains useful chemicals that help in the alleviation of inflammation/swellings. The medicinal chemical can also fight intestinal bacteria. Therefore, the plant is used in the treatment of diarrhea and chronic intestinal catarrh. The leaves and shoots are edible in small amounts because they contain high levels of tannin. The plant produces large quantities of nectar and pollen which make very sweet honey. However, it is advisable to seek the assistance of a physician before using the plant for treatment.
Other Uses
Traditionally, the plant was used to make dyes. The dye was used for hair and food coloring. Some people claim that the roots of the plant are also edible.
Why is Purple Loosestrife Invasive?
One blooming sally plant can produce several millions of seeds in a single season. The seeds are carried by water making dispersion vigorous. Apart from that, the seeds can be carried by muddy shoes, pets or contact with animal fur. The seeds are also dispersed by wind, car tires, and boat trailers. Purple loosestrife stems and roots can also sprout after mowing.
Once the plant flowers, the seeds remain viable in the soil for up to 7 years. The seeds can stay dormant until conditions are favorable for germination.
Lythrum can grow in a wide variety of soils and climate. Unlike most plants, purple loosestrife can withstand changes in weather, soil pH, nutrient levels, and sunlight exposure. The plant has few if any predators in diseases and pests helping it outdo natural vegetation.
The plant forms a canopy-like cover that smothers other plants. Purple loosestrife also hinders animals from accessing sunlight. Initially, purple loosestrife plants were sold commercially but due to invasion, it is illegal to sell the plant in most places. It was also used to control soil erosion and as an ornamental plant.
The Problem of Purple Loosestrife
Because the plant can spread over large areas, it degrades the habitat for other organisms like birds, insects, and plants. Purple loosestrife grows in wetlands which are a habitat for fish, reptiles, mammals, amphibians, and birds. When the plant blossoms in these areas, it chokes out life by reduction of space.
Apart from effects on living organisms, when blooming sally grows near or in water bodies, it blocks irrigation channels. The plant also renders the waterways unnavigable. The weed also hinders recreational and economical activities like boat recreation and fishing. In the long run, purple loosestrife can lead to loss of livelihood for farmers and fishermen. This is why many want to get rid of purple loosestrife in their yard.
The purple loosestrife can also invade dry soils like farmland and construction sites. Infestation by the weed leads to reduced yields and increased cost of production. In case it invades a construction site, it reduces the aesthetic value of the environment if it is not controlled. The plant interferes with decomposition and nutrient cycling leading to a reduction in natural vegetation.
Purple Loosestrife Cultivars
It is difficult to differentiate loosestrife from cultivars. Therefore, in most regions, it is difficult to transport or commercialize cultivars. There are claims that some cultivars are sterile and cannot spread to affect the surrounding vegetation. According to Iowa State University, all cultivars of purple loosestrife are fertile.
Some common cultivars of the plant are Morden Pink, Morden Gleam, Rosy Gem, and Terra Nova. All these species are fertile and a threat to the ecosystem. Some of the cultivars produce as many seeds as the blooming sally.
Control Methods of Purple Loosestrife
To maintain the ecological balance, purple loosestrife should be controlled. If no action is taken, the plant will inhibit the growth of other living organisms. The flowering sally leads to the clogging of irrigation channels and reduces marine life. You should maintain the plant within ecological limits in case you want to maintain it for ornamental purposes. It is advisable to control purple loosestrife before flowering- around April, May, and June.
You can still undertake purple loosestrife control after flowering. However, you should cut the flowers and seeds first and put them in plastic bags before cutting or uprooting the plant. You should avoid shaking the plants because they can release the seeds.
The blooming sally is not easily controllable due to its growth habits and numerous seed production. Chemical, biological and physical control methods can eradicate the plant to acceptable limits. The size, stage of growth, and location of the weed determine the most favorable method of control. You can use a combination of the methods to increase the control effectiveness.
It is essential to note that there is little quantitative and experiential data that has information on the ecosystem impact of purple loosestrife. Therefore, control is based on the potential impact of the plant on the ecosystem and other organisms.
How to get rid of Purple Loosestrife?
There are basically 3 methods to use to get rid of purple loosestrife. Either Mechanically, Chemically or Biologically:
Mechanical Removal
There are various physical weed removal methods. You can use uprooting, digging, and cutting. The method is common in areas where there is a small infestations. Mechanical weed removal requires consistency because a single uprooting, digging or cutting cannot eliminate all the weeds.
Physical removal methods are ideal for fewer than 100 plants. You can use uprooting to eradicate young purple loosestrife plants. You can also use the method in loose soils like sand. It is difficult to use this method to remove old plants because of the extensive roots. You should remove the stem and the roots to prevent the sprouting of broken roots.
Cutting is not the most ideal removal method for purple loosestrife. However, you can use it to prevent the spread of the plant. You should do it before flowering to avoid seed dispersal. You can cut the plant to the base several times to prevent sprouting. After cutting the plant, you can burn them after drying up. Else, you can put the plants in plastic bags for fast decomposition and then dispose them in compost fills.
You can use digging for mature and stubborn purple loosestrife. It is the most effective mechanical method to get rid of purple loosestrife. You should dig several times to eliminate all the weeds from your garden.
Physical removal is limited in terms of area coverage. The method is also time-consuming and labor-intensive.
Physical invasive plant removal is labor-intensive
Chemical Removal
Chemical removal is ideal in heavily infested areas where mechanical removal may be infeasible. In most places, chemical removal of purple loosestrife is regulated. You need permits especially when the plant is near water bodies. Apart from the permits, you should take care not to damage other organisms- both plants and animals. In some countries like Canada, there is no approved chemical to spray purple loosestrife near or in water bodies.
You should use selective spraying to eliminate the unwanted weeds only. Widespread spraying can kill crucial organisms in the soil. Also, if all the vegetation is eradicated, it gives the blooming sally seeds from nearby areas space to germinate and infest the area. In most cases, when applying herbicides in wetlands, you need a licensed professional. You should consult your local authorities to know the necessary procedure.
It is advisable to spray in mid-summer when the plants are easily identifiable. At this period, the purple loosestrife is flowering and has not yet produced seeds. You should follow the correct mixing instructions for maximum effectiveness.
It is best to spray in mid-morning when the plants don’t have dew water. For maximum effect, you should avoid rainy and windy days. The herbicide should settle for at least 8 hours but a day is preferred.
You should put on the necessary protective clothing like gumboots, nose masks, and gloves to avoid contact with the chemicals. In case of mild wind while spraying, ensure you are applying the herbicide towards the direction of the wind.
Unfortunately, most chemicals destroy the ecosystem. It is difficult to get rid of purple loosestrife when using chemical control. The chemicals may interfere with marine life, soil micro-organisms, and natural vegetation.
Biological Removal
This is the most environmental-friendly method. However, the technique is limited because purple loosestrife has very few predators. Galerucella spp. is one of the insects you can use to control Lythrum. Galerucella also gets rid of the flowers, inhibiting further spread of the plant. The leaf-eating beetles are ideal in the removal of a few plants- less than 25.
A root-mining weevil known as Hylobius transversovittatus can also be used to destroy the roots of the plant. A combination of the two insects will work well in removing a small infestation of purple loosestrife.
However, this method is limited because of the unavailability of these predators. Also, the technique is limited in terms of the number of plants it can control. Chemical control of other pests makes it difficult to keep the predators for long. The method also takes time, at times up to 5 years which can be a limiting factor especially in farmlands.
Where the land is heavily infested, it is advisable to use chemical removal. Herbicides eradicate the plants faster and also destroy them to the roots.
Conclusion
Purple loosestrife is a highly invasive plant. It causes massive alteration in ecology because of its growth. The large quantity of seeds after flowering also makes it difficult to control the plant. You can get rid of purple loosestrife through chemical, mechanical, or biological methods. Cultivation, propagation, transportation, and commercialization of the plant is prohibited in most regions.
References
- Department of Natural Resources (DNR):Purple loosestrife control; Herbicides- https://www.dnr.state.mn.us/invasives/aquaticplants/purpleloosestrife/control_herbicides.html
- Northern Dakota University: Identification and control of purple loosestrife- https://www.ag.ndsu.edu/publications/crops/identification-and-control-of-purple-loosestrife-lythrum-salicaria-l
- Minnesota Sea Grant: Purple loosestrife: What you should know, what you should do- http://www.seagrant.umn.edu/ais/purpleloosestrife_info
- Wikipedia: Purple loosestrife- https://en.wikipedia.org/wiki/Lythrum_salicaria
- Department of Natural Resources: What you can do to control purple loosestrife- https://www.dnr.state.mn.us/invasives/aquaticplants/purpleloosestrife/control.html
