Officially, Walla Walla sweet onions are only grown in Washington state's Walla Walla valley. Home gardeners may purchase the seeds or starts for their own vegetable patch, though, and freshly picked sweet onions from Walla Walla seeds or transplants are also found at farmers markets. Walla Walla sweets do not have the longevity of storage onions that are used into the winter months. Ideal for grilling, in sandwiches or salads, the crispy texture and mild, sweet flavor make the onion a favorite summertime menu item.
Cut the green tops off the onion bulb with a pair of kitchen scissors or handheld garden pruners. Leave 1 inch of stem attached to the bulb.
Brush garden soil away from the paperlike outer skin by hand. The Walla Walla sweets may be left sitting outdoors for two to three hours to allow the dirt to dry before cleaning.
Set the onions in a single layer on a shelf in in kitchen pantry, garage or another cool, dry place in the house. Alternately, put the onions in a paper bag and place in the refrigerator.