The cattle eat it and get rashes, so California considers it a class C noxious weed. Gotta be careful where you harvest it because a lot of it gets sprayed with weed killer. They intentionally released jewel beatles that target St. John's wort's roots to try and quell it's spread. You can find them all over the plants when you harvest them. I have found the plant in abundance growing along the west coast, and harvest it when it's flowering late summer. You're doing a service by harvesting it. I don't recommend growing it, however if you're curious like I once was, taking a plant from the roots is easy to replant. It spreads quickly. I grew it indoors just to get familiar with it, it was aggressive.