When hiking in the woods in the spring you'll see this plant almost everywhere you go. It has a white flower in the spring. Because of it's anti-viral and anti-fungal properties it alters the soil properties in the forests, making it hard for other native plants to grow such as spring wildflowers and tree seedlings.
A couple of years ago I volunteered at the Credit Valley Conservation Area - International Biodiversity Day. at a "Garlic Mustard Pull". As a group, for several hours we pulled garlic mustard and collected over forty large leaf bags in just a few hours. We learned alot that day about invasive species. If you have garlic mustard in your garden - don't compost it ! The seeds can last several years in the ground.
Garlic mustard can be used in any recipe that calls for mustard greens. Young plants have a mild mustard flavour with hints of garlic. They can be cooked or eaten raw. Older plants become more bitter and stronger flavour. Once the plant is in flower it will be more bitter. Don't use any plants that have been treated with weed killer. Spring is the best time to pick.
Garlic mustard can be used in salads, mixed with more milder greens. You can steam, simmer or sautee. They can be used in soups, stews and sauces. You can find many recipes using garlic mustard in books and on the internet. On our volunteer day at the conservation area some garlic mustard was pureed and made in to a pesto and served on French bread at lunch time. When the plant goes to seed you can make your own mustard or wild mustard seed mayonnaise.
For more info on Garlic Mustard check out this website - Garlic Mustard Festival