In the spring, the second year growth of the garlic mustard (Alliaria petiolata) really takes off. First a few clusters of basal rosettes appear, meaning a bunch of leaves growing on stems from the ground. Then very soon afterwards, a flower stalk will shoot up. It is topped by a cluster of unopened flowers that look like a small broccoli flowerette, and there are a few triangular leaves growing on the stalk. Before the stalk gets too tall, about 5-8 inches high, we pick them in bunches and cook them as a wonderful green side vegetable with dinner, dressed with butter and salt.
We ordered a great reference book by John Kallas, in Oregon, called Edible Wild Plants: Wild Foods from Dirt to Plate. He has lots of information about leafy greens in the wild, but we disagree with him regarding the bitterness of garlic mustard. In our experiences here in southeast Connecticut, the flower stalks are not bitter at all, and we give them a gentle 3 minute boil to wilt the leaves and stem. The triangular leaves that grow on the flower stalk later in the season, even when the seed pods are present, taste much better to us than the kidney-shaped leaves that grow from the basal rosette all year long. We make a pesto from the tough basal leaves, where the peppery taste is stronger. We even like the green seed pods lightly boiled and served with butter and salt.
We have also managed to make a great mustard condiment from the hard, black seeds. The taste is very fiery, like a horseradish, while the color is a dark brown like dijon. Robert ground them in a coffee mill, and mixed the ground seeds with vinegar, salt, water and honey to make a strong mustard.