Garlic mustard (Alliaria petiolata) comes from Europe and was introduced into North America as a culinary herb in the 1860s. Unfortunately the insects and fungi that live on garlic mustard in Europe aren't as common in North America so it has become an invasive species in many areas including here. I was amazed to find on a recent trip to the UK that garden centres were still selling garlic mustard seeds
When I hid this cache the forest floor was completely covered with a fresh crop of this biennial plant effectively choking off the growth of native species.