Walking onions are a hardy perennial, some calls them forever onions because they continue to produce food until covered with snow in the fall. If pulled, the roots and a small piece of bulb may be replanted. They'll grow a new plant. They may be propagated by planting the bulbils that form on top of the flower stalk, or by digging and dividing the mother clump. New bulbs form beside the flower stalk producing tender bulbs later in the season. 
 
Perennial, cut and grow.