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:

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):

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.