Walla Walla Bulb Onion is a long-day cultivar bred for producing large, sweet bulbs that mature in 100 to 125 days. Named after the Walla Walla region of Washington state, this variety thrives in zones 3 through 10 and rewards early starting with genuinely impressive yields of globe-shaped bulbs. The key to success lies in sowing seeds indoors 10 to 12 weeks before your last frost date, then transplanting outdoors as soon as soil reaches 45°F. Starting early matters here: the longer the growing season, the larger your bulbs will become.
Full Sun
Moderate
3-10
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Walla Walla onions are exceptional sweet onions with a mild, approachable flavor that tastes nothing like the sharp bite of storage varieties. Plant them densely at 6 to 8 inches apart initially, then thin as they grow, and you'll harvest substantial bulbs by midsummer. The variety's cold tolerance in zones 3 through 10 means you can garden with confidence across most of North America, while the straightforward care requirements make this a genuinely accessible choice for anyone learning to grow onions from seed.
These bulbs are grown primarily for fresh eating rather than long-term storage. Their mild, sweet character makes them excellent sliced raw in salads, grilled whole or halved, caramelized for soups and sauces, or roasted alongside other vegetables. Because they lack the pungent sulfur compounds of storage onions, they're prized by cooks who want onion flavor without harsh bite.
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Start seeds indoors 10 to 12 weeks before your average last frost date in soil with a temperature of 60 to 85°F. Sow seeds at a depth of 1/4 inch. Transplant outdoors 4 to 6 weeks before your average last frost date when seedlings have developed.
Transplant seedlings outdoors 4 to 6 weeks before your average last frost date when soil can be worked and has reached at least 45°F. Space transplants 6 to 8 inches apart initially (you'll thin them further as they develop), or use a final spacing of 12 inches for maximum bulb size. Earlier transplanting produces bigger bulbs.
You can sow seeds directly outdoors 4 to 6 weeks before your average last frost date, or as soon as soil can be worked when soil temperature reaches at least 45°F. However, starting indoors is recommended to maximize bulb size.
Harvest bulbs 100 to 125 days after planting when the foliage begins to yellow and fall over naturally. Gently dig around each bulb and lift it from the soil, being careful not to bruise the skin. Cure freshly harvested bulbs in a warm, well-ventilated location (around 70°F) for one to two weeks to toughen the outer papery layers before storage or immediate use.
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