This week is National Invasive Weed Awareness Week. In honor of this, I have decided to highlight some invasive weeds.
As humans have increased in mobility, we have carried with us, either intentionally or unintentionally, species from our homes. Some never become "established" as the individuals that are moved to a new place do form viable populations. Others do become established, but remain in small numbers. Then there are those that become invasive. Free from the pests, competitors, and diseases the plague them in their home range, their populations grow unchecked, often to the determent of other species. In agroecosystems (such as farms and pastures), this can mean a reduction in production. In native ecosystems, this can mean a disruption of ecosystem processes and the decline of native species. In fact, invasive species are considered by some (like the Nature Conservancy) to be the number two threat to biodiversity, second only to habitat destruction.
Purple loosestrife (Lythrum salicaria) is a beautiful plant, with its spikes of purple-pink flowers. Here is a link to more pictures from the Nature Conservancy. It is a perennial plant native to Eurasia. It loves moist soils and, in the past, has been valued as a garden plant. In fact, a few years ago, I bought a book entitled "A Dyer's Garden", published in that listed purple loosestrife as a good plant to grow for dye. I couldn't find the book this morning, but I am fairly certain there was not a warning about the invasiveness of this species.
But, in the United States, this beautiful plant is a destroyer of native wetlands. It can grow unchecked, forming solid stands. This not only crowds out the native wetland species, but can completely block water ways. The native wetland species that are lost are often food and habitat for animals.