Otherwise known as Purple Loosestrife. It’s quite pretty to look at, but is considered an invasive species. Unfortunately it’s growing all around our lake.
According to Wikipedia:
The purple loosestrife has been introduced into temperate New Zealand and North America where it is now widely naturalised and officially listed in some controlling agents. Infestations result in dramatic disruption in water flow in rivers and canals, and a sharp decline in biological diversity as native food and cover plant species, notably cattails, are completely crowded out, and the life cycles of organisms from waterfowl to amphibians to algae are affected. A single plant may produce up to 2.7 million tiny seeds annually. Easily carried by wind and water, the seeds germinate in moist soils after overwintering. The plant can also sprout anew from pieces of root left in the soil or water. Once established, loosestrife stands are difficult and costly to remove by mechanical and chemical means.
Plants marketed under the name “European wand loosestrife” (L. virgatum) are the same species despite the different name. In some cases the plants sold are sterile, which is preferable.
In North America, purple loosestrife may be distinguished from similar native plants (e.g. fireweed Chamerion angustifolium, blue vervain Verbena hastata, Liatris Liatris spp., and spiraea (Spiraea douglasii) by its angular stalks which are square in outline, as well by its leaves, which are in pairs that alternate at right angle and are not serrated.