are these thistles? any specific type that you can determine?

Asked August 14, 2015, 10:16 AM EDT

or nettles? Species name? Thanks!

Montgomery County Maryland

1 Response

Unfortunately, these are both non-native invasive thistles. The first and third photos are Bull thistle ( Circium vulgare) and the middle photo (with flowers) in Canadian thistle. Here is information on that: http://extension.umd.edu/hgic/canada-thistle

While the Canada thistle is a perennial with rhisomes, the bull thistle is a biennial, and they require different control methods. Here is info from our website (note that you must refer back to a list of control methods): http://extension.umd.edu/hgic/problems/herbaceous-invasives-control

The Canada thistle is by far the more problematic. Never let these go to seed and spread. Both are official "noxious weeds" of Maryland because of their agricultural damage.

ECN