Canadian thistle
From Wikinfo
Canadian thistle, called creeping thistle in Europe, Cirsium arvense, is a perennial dioecious (there are both male and female varieties) plant which is generally considered a noxious weed. Canadian thistle widely infests southern Canada but is native to northern Africa and southeastern Eurasia. It is characterized by upright growth, spiny foliage, and small pink-purple flowers. Most distinctive is its habit of propagation though an extensive root system which makes weed control difficult.
Canadian thistle grows well in moist rich soil, it tolerates alkali soils, and light frost although plants in adverse sitiuations will be stunted and not grow to the full size of a vigorous plant in good condition of about 4 feet, (a bit over a meter high). Plants in good condition produce large quantities of seeds with little parachutes which can spread some distance in a brisk wind.
The Canadian thistle is edible, even tasty, although only goats can be expected to enjoy any part other than the root. Control by grazing is one option while mowing accomplishing the same goal of retarding plant growth and also preventing flowering. Cultivation may divide the extensive root system and spread the plant which can propagate from a relativly small piece of root. Biological weed control may be possible using several organisms.
