Garlic mustard is new to me, and I just discovered I'm overrun with it! Last year was my first summer in my new house, and I did a lot of weeding, but I thought the rosettes were something like violets or overgrown Creeping Charlie, and I did not pay them much attention. Now, I see that I have huge areas under my trees that are garlic mustard from end to end. What do I do? From what I can see, they have flowered, but (assuming the seed pods are easy to spot) they have not yet gone to seed. Do I spray with Roundup? Do I weedwack and then rake them up? Do both?
aack! Completely overrun by garlic mustard!
Unfortunately, weed whacking won't control garlic mustard. If you leave roots in the ground, they will grow. If you have a manageable amount, the best thing to do is pull them up by the roots and dispose of them in plastic bags. If they go in a landfill without being bagged, or if you put them in your compost pile you will just be spreading the nuisance. Don't just leave them on the ground; the seeds will develop and disperse from plants left on the ground. Before you discard them, you might want to harvest the leaves, as they make a tasty pesto.
If you have a really large patch that is too much to pull by hand, Roundup is the way to go.
I have had some luck using a strong mix of Roundup on Creeping Charlie when it is in bloom. Try that?
I pull and pull and pull. For me, they are easier to pull when they are mature, then when they are small. Also, do your best to make sure they don't seed.
Hope all the plants you got from me are doing great.