The past few weeks I have been hunting. Hunting for a specific invasive plant that blooms mid-summer — purple loosestrife. This plant lures you in with its bright purple flowers and robust form as it grows along the riverbanks and sandbars of the Kankakee River watershed and beyond. I can’t deny its beauty, but at the same time it has the potential to be a scourge.

Purple loosestrife is an invasive wetland plant that began to show up in New England back in the 1830s, as its seed was carried to North America in ship ballasts from Europe, Asia and Africa. Today it can be found across most of the United States and lower part of Canada.

Why has it been so successful? As I mentioned before, it is a striking plant that you might want in your garden and people have spread it that way, but it also can produce a couple million seeds per plant which allows it to colonize flooded wetlands and waterways quickly.

Once a population gets rooted in our other local native species start to get pushed out, and it’s very difficult to completely eliminate with that kind of seed source. Some direct competitors I see along the Kankakee would be swamp milkweed, the halberd leaved rose mallow, native sedge communities, water willow and others that are core to the habitat in our watershed. I value the biodiversity of a native functioning plant community and put my stewardship efforts toward that structure.

For the areas I manage there are only a handful of purple loosestrife plants growing in wetlands and ditches here and there each year, but I’ve seen fields of it in unmanaged areas nearby that cause me to drop what I’m doing to remove any individual plant I find. Like any invasive species, early detection and action is the best.

I dug up the plant in the photo here to show my new crew members what it looks like. It is 3-5 feet tall generally, has a square stem, very bright and abundant flowers, and blooms for us in July and August. If you know where patches from past years are, you might be keen to search for the square stems and find it in the early summer before bloom time. Its weakness however is the flowerhead, as once in bloom it is easy to spot.

Keep an eye out on your hikes along the Kankakee River and adjacent waterways for purple loosestrife and do what you can to stop the spread to keep our river system healthy.