I was surprised when confronted with a list of invasive plants to find that I myself had several of them. I had already known about the Shepherd's Crook Lysimachia clethroides. I had to constrain the beast with a barrier to keep it from devouring everything beyond its reach. I keep it as Kay likes to use it for cut flowers. Its other name is Gooseneck Loosestrife. Need I say any more. That other evil, Purple Loosestrife, Lythrum salicariais, is taking over the world. The emphasis for these two is the strife when they get loose. All over the Northeast U.S., where I live, any field or roadside containing a bit of moisture has been invaded with these purple flowered plants. That particular loosestrife is driving out native species. There are fewer cattails when purple becomes predominant.
Some alien plants were purposely introduced as they had beneficial properties that were used by people in their mother country. In their new environment, without the old conditions or predators to keep them in check, they overwhelm native species and are running amok. Other exotics arrived piggyback with other imports. Invasive plants threaten biodiversity and result in great cost to keep them under control. Some have names that identify their undesirable nature such as Koster's curse and mile-a-minute weed, Polygonum perfoliatum, also known as Devil's tail tearthumb. No mistaking these plants as being gentle. Others, as in lily-of-the-valley, seem much more benign. I planted several lily-of-the-valley in a moist, shaded spot. While I was not looking, these plants proliferated to an alarming degree, taking over a most extensive area. An equally aggressive counter attack with a spade was necessary to keep them in check.
This past summer I happened to enjoy a visitor's center in the Adirondack Mountain Park. There, at a butterfly house, were some Common Mullein Verbascum thapsus, planted to attract butterflies. A single plant can have from "100,000 to 180,000 seeds that remain viable for more than 100 years". The Mullein was originally brought from Europe for medicinal purposes. Its spread can be bad medicine.
Japanese Knotweed plants, originally introduced as ornamentals and for landscape screening, are now invasive aliens. The Teasel, Fuller's Dipsacus fullonum, was imported to card wool back in the old days. Today it is used in flower arrangements but Kay does not pick enough to keep it down.
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