There are certainly some striking thistles that have use in the garden, but Bull Thistle (Cirsium vulgaris, pictured above) and Canada Thistle (C. arvense) are not included. These thorny invaders usually behave as biennials, forming a rather large (and rather prickly) rosette the first year, then launching a pink to purple flowerhead several feet skyward the following summer.
C. vulgaris can be controlled by hoeing or pulling, but I recommend thick leather gloves before laying hands on the plant! C. arvense is more problematic, and may require several repeat performances - even small parts of the rootstock are able to generate a new plant. There's another reason these are good candidates for the trash: Once they have begun to flower, they often can set seed even if completely uprooted.
It's easy to control this weed by hand pulling, but it's hard to bring yourself to do it! A very aggressive biennial, it seeds prolifically; but the goldfinches love it! The "Canadian" version is an even more serious pest.
Family: Asteraceae (Compositae)
Common Name: Thistle
All contents © Travis Saling
This page was last updated November 18, 2013