"Walla Walla" onions (Allium cepa “Walla Walla”) produce sweet mild-flavored bulbs reaching 2 to 4 inches in diameter with stalks growing up to 36 inches high. They are considered a long day onion variety, which means they need 14 to 15 hours of daylight to form bulbs. "Walla Walla" onions are suitable for container growing, which allows the plants to be moved in and out of shelter. Onions in containers grow well in areas that are not normally used for gardening.
Sterilize a used 12-inch deep container by washing it in soapy water and rinsing it with a mixture of one part bleach to nine parts water. Air-dry the container so the soil does not form mud around the edges. Mix together equal parts of potting soil and well-rotted compost. Fill the containers to within 3 inches of the rim.
Place the "Walla Walla" bulb sets on the soil 3 to 6 inches apart, depending on the desired size of the bulbs. Place the sets 1 inch apart if some of the onions are planned for green onions. Sprinkle enough soil on top of the onion sets to cover the bulbs. Leave the tips showing above the soil.
Move the onion container into an area with at least six hours of direct sunlight. If temperatures soar during a summer heat wave, move the container to a shaded spot in late afternoon.
Water whenever to top of the soil begins to dry out. Onions have shallow roots, so do not let the soil dry out, because the lack of water creates smaller bulbs. Pour water into the top of the container until it runs out the bottom. Keep watering the onions throughout the season until the leaves begin to yellow and droop.
Feed the "Walla Walla" onions fish emulsion or a half-strength solution of water-soluble 5-10-10 fertilizer each month. If white salt buildup appears on the top of the soil, flush the plant pot with clear water until the salt disappears.
Check each week for aphids, thrips and spider mites. Spray the onion tops with a strong stream of water to knock off small garden pests off the leaves. Slugs also like to eat the tops off onions. Surround the rim of the container with a thick copper wire to repel the slugs or sprinkle slug bait around the plant pot.
Thin the onions as they grow if they are planted close enough for green onions. Grasp the young onion close to the ground and pull up. To obtain full growth of the "Walla Walla" bulbs, thin them to 5 to 6 inches apart. The tops can be snipped off throughout the growing season to use in cooking. Once the leaves fall over and dry out, dig the bulbs with a hand trowel. Brush the soil off the bulbs. Do not get them wet or they may split.
Things You Will Need
- Large container
- Potting soil
- Well-rotted compost
- "Walla Walla" onion sets
- Fish emulsion
- Copper wire
- Hand trowel
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