[Wikipedia] Origin, Die Back, Spread: Allium vineale (wild garlic, onion grass, crow garlic or stag's garlic) is a perennial, bulb-forming species of wild onion, native to Europe, northwestern Africa and the Middle East.[2] The species was introduced in Australia and North America, where it has become an Invasive species.
Die back
During summer, just like domesticated garlic (A. sativum), after it forms the flower, the plant dies back over the course of the last summer months and sprouts back in mid autumn when precipitations grow and temperatures drop enough.
This is one of the reasons why the plants can be quite easily spread and become a weed, because during the most intense agricultural soil mechanical interactions, the weeds are almost impossible to identify, and both the bulbs and newly formed bulbils are dormant and less susceptible to die from mechanical damage. (link added by Mary Ann Machi)