Allium cepa Seeds | Walla Walla Onion
LATIN NAME: Allium cepa
COMMON NAME: Walla Walla Onion
Plant Profile
This onion is built for fresh eating, where its size and sweetness turn a plain dish into something special. It is the onion of the hamburger stand and the garden salsa.
A thick raw ring of Walla Walla on a burger or a tomato sandwich needs no cooking to be pleasing, because the flesh is crisp and the bite is soft. The wide rings also grill beautifully, caramelising at the edges while staying tender in the middle.
Science & Biotechnology
The mildness of a Walla Walla is measurable: it carries far less of the sulphur precursor that makes other onions fierce, and what it does carry is balanced by a real load of sweet, healthful compounds in the flesh.
Like other alliums, the bulb accumulates quercetin, a flavonoid antioxidant concentrated in the outer scales and prized in nutrition work on the genus. In the Walla Walla the quercetin sits inside a flesh that is already low in pyruvic acid, so the eating experience is gentle and slightly sweet rather than sharp, which is why the cultivar is studied as a model for mild onion breeding.
Breeding records describe the Walla Walla as high in soluble solids and low in the pungency markers, a combination that reads on the tongue as juice and sugar more than heat. The alliinase cascade still runs when the bulb is cut, but the precursor pool is small, so the volatile bite fades almost at once.
Uses & Benefits
The Walla Walla sweet onion traces to a sweet Italian seed, the ‘Fontina’ type, carried to Washington Territory by a French soldier in the 1880s, who found the loose, sandy loam around Walla Walla let the mild bulb swell to jumbo size with almost no bite. That happy accident became a protected regional onion, so sweet that locals eat it raw like an apple, and the cultivar remains the standard for anyone who wants an onion that disappears into a salad instead of dominating it.
The Walla Walla forms a large, flattened-globe bulb with a single centre and a notably thin, pale, papery skin that bruises more easily than a storage onion’s. The flesh is crisp, juicy, and white, with a high water content that keeps the texture succulent and the rings wide. Hollow, blue-green leaves stand in a broad fan, and the neck is looser than a keeper’s because sweetness was bred ahead of storage life.
The long, cool growing season of its home valley lets the bulb build soluble sugars slowly while the pungent precursors stay low, so the balance tips toward sweet rather than hot. That same chemistry means the bulb does not store for months like a Southport globe; it is a fresh-eating onion meant to be enjoyed in the weeks after lifting, not banked for winter.
Minced into a fresh salsa or a cucumber salad, the bulb adds allium depth without the harsh aftertaste that would overwhelm delicate summer produce. Cooks reach for it exactly when a stronger onion would be too much.
Growing from Seed
The sweet bulb wants the loose, sandy, well-drained ground that made its name, with steady moisture and full sun. A medium of two parts sandy loam, one part compost, and one part coarse sand mimics the Walla Walla valley and lets the globe size up.
Sow the fine black seed in a shallow drill as the soil warms in spring, covering with the thinnest layer of fine soil or vermiculite and keeping the surface even. Thin early so each plant has light and air around its leaves.
Begin thinning when the seedlings show their third true leaf, pulling the weakest to leave a hand’s width between plants; reach a final spacing near twelve centimetres once they carry six true leaves and a sturdy stem. Lift the bulbs when the tops fold, and eat them fresh, because this is not a long-keeping type.
Our Take
The Walla Walla is the only onion I eat like fruit, and a fresh slice on a summer tomato is hard to beat. The Onion Allium cepa is the everyday bulb, while the Southport White Globe Allium cepa ‘Southport White Globe’, the Dutch Shallot Allium cepa (Aggregatum), and the Garlic Chives seed Allium tuberosum fill the rest of the allium plot.
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