Photos are representative and may not match your specific variety.

Walla Walla Sweet Onion

Allium

Allium cepa

Overview
Juicy, sweet, regional favorite. In the Northwest, which has normal low winter temperatures above -10°F (-23°C), seed is sown in late August, and a crop of very large, flattened, ultra-mild onions is harvested early the next summer. SPRING PLANTING: Walla Walla may be spring planted using seeds or plants in colder regions where winter survival is hit or miss. It is not as big or sweet as the wintered-over crop, but still milder and juicier than others from spring planting. Nice as a "green top" onion. Not for storage. Adaptation: 35-55° latitude. Also offered organic, and as plants.
Planting
Start seeds indoors 10-12 weeks before last frost. Transplant when soil can be worked in spring. Can also plant sets in early spring.
Growing
Sun: full. Water: high. Soil pH: 6–7. Space plants 4" apart. Germination: 10-15.
Pests & diseases
Common pests: Onion thrips, onion maggots, cutworms. Common diseases: Pink root, fusarium basal rot, downy mildew, purple blotch.