Invasive Species

By: Punit Chohan

Purple Loosestrife: Is it a beauty or a beast?

  • Lythrum salicaria L.

This plant is an origin from European descent, and has spread to North America rapidly in the wetlands. The plant was introduced both as a contaminant of European ship ballast and as medicinal herb for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores. Purple Loose-strife grows in a wide range of habitats. These plants can reach height of 2m with 30-50 stems forming. One “mature plant” can produce more than 2 million seeds annually. Purple loose strife look very elegant but is an aggressive invader to biodiversity. This is a perennial herb with tall spikes of magenta flowers. During the summer it grows in wet areas such as marshes, swamps, and river banks.

What is the threat to Biodiversity and why is it important for people to be aware of it?

The threat of Purple Loose-strife to Biodiversity affects many of the wetlands in North America. It is the most prevalent invasive species, covering about 400,000 acres of federal land, including marshes, pastures and riparian meadows. Since 1880 infestation of native habitat by purple loosestrife has been occurring at an exponential rate, and it has tripled in area since 1940. . It also remains possible that after several years of minimal impact on species diversity, purple loosestrife may reach a threshold biomass after which it becomes dominant.

What is the cause of the threat?

Purple loosestrife is such a harsh invader, which can rapidly degrade wetlands and destroying their value for wildlife habitat. In North America, wetlands are the most biologically diverse and productive component for our ecosystem. Hundreds of species of plants, birds , mammals, reptiles, insects, fish and amphibians rely on healthy wetland habitat for their survival. Furthermore, purple loosestrife find their place in a habitat where fish and wildlife feed and seek for shelter to reproduce, becomes choked under a sea of beautiful purple flowers making it a harder place to live. Areas where wild rice grows and is harvested are degraded. An estimated 190,000 acres of wetlands, marshes, pastures and riparian meadows are affected in North America each year. As a result this creates a plentiful of economic impacts of millions of dollars.

Invaders in Our Waters - Purple Loosestrife

What are the impacts of the threat to the organisms in the different kingdoms in that region?

Kingdom Plantae – Plants

Subkingdom Tracheobionta – Vascular plants

Superdivision Spermatophyta – Seed plants

Division Magnoliophyta – Flowering plants

Class Magnoliopsida – Dicotyledons

Subclass Rosidae

Order Myrtales

Family Lythraceae – Loosestrife family

Genus Lythrum L. – loosestrife

Species Lythrum salicaria L. – purple loosestrife

What are anatomical or physiological characteristics of each organism that make them vulnerable to this threat?

Plantae- Can choke out potentially rare and endangered species of native plants. Plants holds little food value, cover and nesting material for animals and leads to a reduction in habitat diversity.

Vascular Plants-Gymnosperms, allows vascular plants to evolve to a larger size than non- vascular plants, which lack these specialized conducting tissues and are therefore restricted to relatively small sizes.

Seed Plants- Many seed plants are large. Their seeds mature inside cones. Seeds may be carried away from the parent plant by wind, water, or animals. The seeds make it harmful for wetland and wildlife.

Flowering Plants- Angiospermae or Magnoliophyta, are the most diverse group of land plants. Plant that produces seeds within an enclosure, in other words, a fruiting plant. Estimated to be in the range of 250,000 to 400,000.

Dicotyledons- Leaves grow 'adult' like and again the plant is invasive destroying wetlands

Rosidae- Sub-class same as the flowering plant process

Lythraceae-620 species of mostly herbs, with some shrubs and trees. Petals being crumpled in the bud and the many-layered outer integument of the seed

Lythrum salicaria- Purple Loosestrife

What are actions that humans can take to reduce/prevent the impacts of this threat?

To prevent the crucial control of purple loosestrife, is to start controlling them in the summer season; in June, July and early August. Purple loosestrife can easily spread if improper control methods are used. Pulling, cutting, or digging plants in these manageable infestations will limit the spread of purple loosestrife beyond the area of heavy infestation. Making sure that an individual is aware that their clothes and equipment may transport the small seeds to new areas. Thoroughly brush off your clothes and equipment before leaving the site. Proper disposal is a huge concern, because it is important to put all plant pieces in plastic bags as vegetation can rot quickly in plastic; and bags should be taken to a sanitary landfill site. Composting is not to be done as purple loosestrife seeds may not be destroyed and the thick wood stem and roots take a long time to decompose. By making a difference like this will help avoid purple loosestrife.
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With your help, wetlands like this can remain healthy!

Biological Control of Purple Loosestrife


  1. Purple Loosestrife | Ontario’s Invading Species Awareness Program. Retrieved December 20, 2015, from
  2. What you can do to control purple loosestrife! Retrieved December 22, 2015, from
  3. Purple Loosestrife: What you should know, what you can do | Aquatic Invasive Species | Minnesota Sea Grant. Retrieved December 19, 2015, from