Walla Walla Onion

ABOUT THE PLANT

Description: This long-day Walla Walla onion is a medium to large (2-6") onion with almost translucent, pale flesh that is firm, crunchy, and juicy. The bulbs are squat and globe-shaped with yellow-to-light-brown parchment-like skin.  These onions are prized for their sweet and mild flavor when raw, and their sweet, warm flavor when cooked They grow in the area of Walla Walla, Washington, and in northeastern Oregon.

Origin:

In the 1880s, Peter Pieri from the west coast of Italy, brought sweet onion seeds to Walla Walla, Washington and eventually developed a larger, sweeter, rounder onion that became known as the Walla Walla Sweet.

Usage: Use raw for salads and sandwiches and as a garnish. Use cooked wherever onions are called for.

Interesting facts: Walla Walla onions are sweet due to having half the sulfur content of ordinary onions, which means they are milder and less likely to cause tears.

HOW TO GROW

General requirements: Long-day onions require 14 or more hours of full sun to form bulbs. For this reason, they are best grown in northern climates where the days are longer during the growing season. Optimum soil temperatures are 60-75ºF and optimum pH is 6.0-7.0. Onions need fertile, well-drained sandy loam soil amended with compost. Fertilize with fish emulsion or compost tea every few weeks. Consistent and adequate water is the key to optimum growth. Keep the soil moist, but never soggy.

In the garden: Plant early to mid-spring when the soil temperature reaches at least 55 ºF. Sow 1-3 seeds ¼-½" deep, per every inch. When seedlings are 2-3 inches tall, thin to 2-6” apart. The larger the bulb size the more space they require. Keep soil consistently moist, but not soggy. Onion roots are shallow so a light watering will suffice.

In containers: To raise bulb onions, you'll need a well-draining container wide enough so that each onion has about 3 inches of space around it.  Fill it with good potting soil and place it in an area that will get 14 or more hours of sunlight each day. Plant seeds ½"deep, 1” apart.  Once the seedlings are an inch or so tall, keep the best-looking plants by snipping out the rest and ensuring that each remaining seedling is 4-6" away from its neighbors. Fertilize with fish emulsion or compost tea. Do not feed nitrogen-heavy fertilizer past mid-July.

Transplanting: Start 8-10 weeks before the last frost date in your area. Scatter seeds in flats 1/4-1/2” deep, about 1/4” apart in seed starting mix. Place in a warm, bright spot. You may need to use grow lights to get 14 or more hours of light per day. Liquid fertilize seedlings every 7- 10days. Fish emulsion or compost tea is ideal. Before transplanting, clip the tops down to about 3 inches and harden-off for about a week. Then transplant seedlings out 2-6” apart. Seedling size should be about the thickness of a pencil at transplanting time.

HARVESTING

Bulbs:  Onions are ready to harvest when the green tops turn yellow, dry out, and fall over, but they can also be harvested quite early and used as green onions. Pull by hand or use a garden fork to dig them up. Brush off loose soil and let them sun-cure for a few days. Then move to a protected area for further drying. Refrigeration is your best bet for long-term storage of sweet onions. Cut off tops and roots and wrap separately in newspaper before refrigeration.

Seeds: Onions are biennials which means they flower in their 2nd year. To save seed from onion, select several perfect onions and store them in a cool, dry area until the following spring. Try to replant them at the same depth as when you dug them up. They will begin to send up new growth and eventually a flower stalk. By late summer the flowers, then seed heads will begin to form. As the seed heads dry the seeds will begin to fall out.  Remove the seed heads and place them into a paper bag. Shake the bag to release the remaining seeds, then separate the seeds from other debris.  After assuring that the seeds are dry, store them in a cool, dry place.  

FAST FACTS

Common name: Walla Walla sweet

Latin name: Allium cepa

Growth habit:

Life cycle: biennial, but grown as an annual

USDA Zones: best in zones 3-6

Seeds per ounce: ~8000