Walla Walla Onion Seeds Allium cepa are a traditional bulb variety known for producing large round onions with smooth outer layers This onion variety develops upright green foliage that supports steady bulb formation beneath the soil during cool to mild seasonal conditions The plants produce uniform bulbs that mature gradually as the foliage develops This heirloom onion variety is valued for structured plant growth and consistent bulb development making it a widely recognized onion variety suitable for seasonal cultivation