The purple flower heads may look pretty, but don't let that fool you. Milk thistle (Silybum marianum) can be a pain if it's growing in your yard.
It's non-native and can be an invasive plant, as Keri Wilson, horticulturist and writer for Garden Media Group, points out, noting that it's classified as a noxious weed in several states. It spreads by seed that can remain viable for years, she adds, and 'has the potential to destroy an ecosystem and create a monoculture'.
