Onion Types: Storage, Sweet and Spring Varieties – Which to Grow for Your Day-Length and Zone
Walk the produce aisle or flip through a seed catalog and you’ll find a dozen onion types — each with a different shape, flavour profile, storage life, and cultural requirement. The mistake most gardeners make is choosing varieties by appearance alone, then wondering why their sweet onions turned sharp, or why their bulbs stayed golf-ball small. Day length — not soil or fertiliser — is the single biggest factor controlling whether an onion bulbs at all, and matching variety to your latitude is non-negotiable.
This guide breaks down all five onion categories — storage, sweet, red, spring, and specialty — with the mechanism behind each, the best US varieties in each group, and a complete comparison table to help you choose the right type for your garden and kitchen.
For everything from planting depth to soil preparation, see the complete onion growing guide. Here, the focus is entirely on type selection.
The Day-Length Mechanism: Why Variety Choice Starts with Your Latitude
Onions are long-day, short-day, or day-neutral (intermediate) — terms that describe the minimum photoperiod needed to trigger the plant to stop producing leaves and start forming a bulb. Get this wrong and no amount of good soil will save you.
When day length hits the critical threshold, the plant redirects all energy from leaf production into bulb formation. Each green leaf that has already formed corresponds to a concentric ring inside the bulb — more leaves before bulbing equals bigger bulbs. This is why northern gardeners can grow massive storage onions: long summer days allow many more leaves to develop before the bulbing trigger fires.
Long-day varieties (14–16 hours) are bred for USDA zones 3–6 — the northern two-thirds of the US. They form bulbs only when summer days are longest, giving northern gardens ample time to build up leaf mass first. Planted in the Deep South, they will sit green all winter and refuse to bulb before summer heat kills them.
Short-day varieties (10–12 hours) are the right choice for zones 7–10 — the South, Gulf Coast, Southwest, and California Central Valley. Planted in fall, they overwinter as seedlings and bulb in spring as days lengthen to their lower threshold. In the North, they would bulb prematurely in early spring when bulbs are still tiny.
Day-neutral (intermediate) varieties span zones 5–7, bulbing across a wider day-length range (12–14 hours). They are the most forgiving option for mid-latitude gardeners unsure which camp they fall into.
Storage Onions: The Pantry Workhorse
Storage onions are the brown-papery, pungent bulbs most Americans picture when they think of an onion. Their assertive flavour comes from high sulfur compound concentrations — the same chemistry that makes them eye-watering when raw and richly savoury when cooked. Those sulfur compounds also act as a natural preservative, giving cured storage onions a shelf life of 6–12 months under the right conditions.
Yellow Storage Onions
Yellow onions account for roughly 87% of US commercial onion production and are the default choice for roasting, sautéing, soups, and caramelising. High pyruvate content drives their pungency, and the Maillard reaction during cooking converts that sharpness into deep sweetness — the reason French onion soup works as well as it does.
Top varieties for home gardeners:
- Copra — the gold standard for northern long-day storage; cures to a tight, dry skin with a shelf life of 10–12 months. Zones 3–6.
- Patterson — disease-resistant, good yield, stores reliably to 10 months. Zones 4–6.
- Stuttgarter — a classic intermediate; tolerates wider day-length ranges, smaller bulbs, excellent storage. Zones 4–7.
- Candy — day-neutral, mild-to-medium pungency, stores 3–4 months; a practical bridge between storage and sweet. Zones 5–7.
Yellow storage onions are the best first choice if your goal is a kitchen-staple crop that fills a cool pantry shelf through winter.
White Storage Onions
White onions share the same high-sulfur chemistry as yellow, but carry a slightly sharper, cleaner bite with less complex flavour depth. They are the onion of choice for Mexican cuisine, fresh salsas, and ceviche — dishes where you want direct onion punch without the yellow variety’s earthy undertone.
Key varieties include White Lisbon (dual-purpose: storage bulb or scallion), Evergreen Hardy White (cold-tolerant, suited to northern gardens), and White Spanish (large, mild-to-sharp, day-neutral, stores 4–6 months). White onion skins are thinner and less protective than yellow, making them marginally more susceptible to storage rot — a practical consideration when planning a large crop.
Sweet Onions: Mild, Versatile, Short-Lived
Sweet onions are the opposite of storage types in almost every measurable way. They are high in water, low in sulfur, and contain elevated sugar concentrations — characteristics that deliver the famously mild, almost fruity flavour of a Vidalia. They are also the shortest-lived: 1–2 months at most under refrigeration.
The sweetness is as much a soil-chemistry effect as a genetic one. The Vidalia onion is legally defined as a Granex-type onion grown in a specific 20-county region of southern Georgia, where low-sulfur sandy loam soil limits sulfur uptake regardless of the variety. The same seed grown in sulfur-rich soil produces a noticeably sharper onion.
Most sweet onions are short-day varieties originating in the South, developed for fall planting and spring harvest:
You might also find growing forsythia guide helpful here.
- Vidalia / Granex — the definitive Southern sweet; flat-to-round shape, cream-white flesh, short-day. Zones 7–10.
- Walla Walla — a Pacific Northwest exception; the only major commercial long-day sweet onion, adapted to Washington State’s mild maritime climate. Zones 6–8.
- Texas 1015Y SuperSweet — day-neutral, productive, and the most flexible sweet variety for mid-latitude gardeners. Zones 6–9.
- Ailsa Craig — a Scottish heirloom long-day sweet known for enormous size; best eaten fresh. Zones 4–7.
Because sweet onions have high water content and thin skins, they bruise easily and do not cure well. Store them individually wrapped in the refrigerator and use within 6–8 weeks of harvest.
Red Onions: Colour, Crunch, and Moderate Heat
Red onions get their signature deep burgundy-to-purple colour from anthocyanins — the same flavonoid pigments found in red cabbage, blueberries, and cherries. A 2019 University of Guelph study found that the outer layers of red onions are particularly rich in quercetin, a flavonoid with demonstrated antioxidant and anti-inflammatory properties in laboratory studies.
In terms of flavour, red onions sit between storage and sweet: moderate pungency, mild enough to eat raw in salads or pickled in a quick brine, assertive enough to hold up on a grill or in a roasted vegetable tray.
Popular varieties for US gardeners:
- Red Wing — long-day, deep colour, stores 6–8 months. Zones 3–6.
- Cabernet — long-day, intense burgundy, tight-skinned, excellent storage through winter. Zones 4–7.
- Red Candy Apple — day-neutral sweet-red cross; mild flavour, shorter storage at 3–4 months. Zones 5–8.
- Red Torpedo (Tropea) — Italian heirloom, elongated shape, very mild, short-to-intermediate day length. Zones 6–9.
One practical note: anthocyanins are pH-sensitive. Cooking red onions in an acidic environment (tomato sauce, vinegar) can turn them bright pink; alkaline conditions shift them toward blue-grey. This is purely cosmetic but worth knowing if presentation matters in your dish.
Spring Onions, Scallions, and Green Onions
This category often confuses home gardeners because the terminology overlaps significantly. The practical distinction:
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→ View My Garden Calendar- Scallions (green onions) — any onion harvested before it forms a bulb. The entire plant is eaten: white base, green tops, and all. Most bunching varieties are purpose-bred to never form a bulb regardless of day length.
- Spring onions — immature bulbing onions harvested early in the season, when the bulb has begun to swell but is still small (marble to golf-ball size). They have a more pronounced bulb than scallions but remain mild enough to eat raw.
Bunching varieties bred specifically for scallion production include Evergreen Hardy White (cold-tolerant, perennial in zones 6+), Tokyo Long White (fast-maturing, slender, mild), and Red Beard (red-tinged bunching onion, decorative and productive).
Because day length does not trigger bulb formation in most bunching types, they are far more zone-flexible than bulbing onions. Most reach harvest in 60–80 days from transplant. For companion planting strategy, green onions work especially well interplanted with heavy-feeding vegetables — their root chemistry deters certain soil pests. See the companion planting guide for the spatial logic behind onion–vegetable pairings.
Specialty Onions: Shallots, Cipollini, and Pearl Onions
Specialty types are where onion growing becomes most rewarding for the kitchen gardener — each has a distinct chemistry and culinary use case that separates it from the mainstream categories.
Shallots
Shallots (Allium cepa Aggregatum group) grow in clusters of two to eight small, elongated bulbs per set. Their flavour is a refined cross between onion and garlic — milder than either, with a subtle sweetness and none of the harsh bite of a raw storage onion. French cuisine’s insistence on shallots in sauces is not snobbery; the chemistry is meaningfully different. Shallots have a higher ratio of delicate flavour compounds relative to pungency compounds, which is why they do not overwhelm a butter sauce the way a minced yellow onion would.
They are grown like garlic: planted as individual cloves (sets) in fall or early spring, then multiplying underground. French Gray Shallot (Allium oschaninii) is considered the culinary gold standard, with a more complex, garlicky flavour. Dutch Yellow is more productive and easier to source across the US. Both store well — 6–8 months in a cool, dry location.
Cipollini Onions
Cipollini (pronounced chip-oh-LEE-nee) are flat, saucer-shaped Italian heirloom onions with papery golden-tan skin and cream flesh. Small at maturity (1.5–2 inches in diameter), they are intensely sweet and extremely high in natural sugars — which makes them ideal for caramelising whole, roasting in olive oil, or pickling in balsamic vinegar. Unlike many sweet onions, they also retain moderate sulfur content, giving them more flavour complexity than a Vidalia when cooked.
Borettana is the most widely available cipollini variety for US gardeners; it is a short-to-intermediate day type that performs well in zones 5–9.
Pearl Onions
Pearl onions are purpose-bred to form small bulbs at maturity (0.75–1.5 inches in diameter). Available in white, red, and yellow, they hold their shape beautifully in stews, braises, and glazed preparations. Snow Baby (white), Purplette (red), and Gold Pearl (yellow) are popular choices for home gardeners.
Peeling pearl onions raw is genuinely tedious; the accepted technique is blanching in boiling water for 30 seconds, then slipping the skins off. Once peeled, they store 3–5 months and are far easier to work with than trying to peel them while raw and firm.
Onion Type Comparison
| Type | Flavour Profile | Storage Life | Best Use | Day-Length Requirement |
|---|---|---|---|---|
| Yellow storage | Pungent, complex, sweetens when cooked | 6–12 months | Roasting, soups, caramelising | Long-day (zones 3–6) or day-neutral |
| White storage | Sharp, clean bite, less complex | 4–6 months | Salsas, Mexican dishes, raw | Long-day or day-neutral |
| Sweet (Vidalia-type) | Mild, almost fruity, very low pungency | 1–2 months (refrigerated) | Fresh, salads, light sautés | Short-day (zones 7–10) mostly |
| Red | Moderate pungency, slightly sweet, colourful | 4–8 months | Salads, pickling, grilling | Long-day or day-neutral |
| Spring / scallion | Mild, grassy, fresh | 1–2 weeks (refrigerated) | Garnish, Asian dishes, stir-fries | Day-neutral (no bulb trigger) |
| Shallot | Delicate onion-garlic hybrid, refined | 6–8 months | Sauces, dressings, French cuisine | Long-day (planted as sets) |
| Cipollini | Sweet, moderate complexity when cooked | 4–6 months | Roasting whole, pickling, caramelising | Short-to-intermediate |
| Pearl | Mild to moderate, holds shape well | 3–5 months | Stews, braises, glazed preparations | Varies by colour; mostly day-neutral |
Choosing the Right Onion for Your Garden
The decision tree is simple once you know your USDA zone:
Zone 3–6 (northern US): Start with long-day storage types — yellow (Copra, Patterson) or red (Red Wing, Cabernet) — for your main crop. Add Ailsa Craig or Walla Walla for a sweet-onion option. Include a bunching variety such as Tokyo Long White for a continuous scallion supply from spring through fall.
Getting the timing right is half the battle — see growing hepatica guide.
Zone 7–9 (mid-South, Southwest, Pacific Coast): Short-day types such as Granex and Texas 1015Y SuperSweet are the most productive for spring harvest. Intermediate types (Candy, White Spanish) extend the season. Avoid long-day storage varieties — they will not bulb reliably at southern latitudes.
Zone 10 (Deep South, Hawaii, southern California): Stick exclusively to short-day types. The growing window is autumn through spring; summer heat shuts down onion growth entirely. Maui and Granex types thrive here.
Pair onions with low-growing companions that will not compete for light. Onions interplanted near tomatoes can reduce certain soil pests; the volatile sulfur compounds released by onion roots deter some thrips and nematodes. If you are planning a kitchen vegetable bed that combines both crops, the tomato growing guide covers vertical space planning that integrates well with onion beds.
Frequently Asked Questions
What is the difference between a storage onion and a sweet onion?
The core difference is sulfur content. Storage onions are high in sulfur compounds, which drive their pungency and act as a natural preservative — allowing them to cure and store for up to 12 months. Sweet onions have low sulfur content, often the result of growing in low-sulfur soils; they are mild and high in water content, but last only 1–2 months and do not cure properly for long-term storage.
Can I grow Vidalia onions outside Georgia?
The name “Vidalia” is a legally protected regional designation restricted to onions grown in a specific 20-county area of Georgia. You can grow Granex-type onions (the variety used for Vidalias) anywhere with the right climate and low-sulfur soil, and the flavour will be similar, but they cannot be marketed as Vidalia onions outside the designated region.
Why do my onions form small bulbs?
The most common cause is a day-length mismatch — a long-day variety planted in the South, or a short-day variety planted in the North. The bulbing trigger fires before the plant has built enough leaf mass to support a large bulb. Other causes include starting transplants too late, overcrowding reducing each plant’s leaf count, or nitrogen deficiency slowing leaf development during the early growing phase.
Are shallots a type of onion?
Botanically, yes. Shallots are classified within Allium cepa (the Aggregatum group), making them a subspecies rather than a distinct species. In practice, they are grown differently — planted as cloves rather than seeds or transplants, multiplying by division — and their flavour is substantially more delicate than bulbing storage onions.
How long can I store different onion types?
Properly cured yellow storage onions last 6–12 months in a cool (35–50°F), dry, dark location with good airflow. Red storage onions: 4–8 months. White storage: 4–6 months. Sweet onions: 1–2 months refrigerated. Shallots: 6–8 months. Cipollini: 4–6 months. Pearl onions: 3–5 months. Spring onions and scallions: 1–2 weeks refrigerated. Never store any onion type in an airtight container — airflow is essential to prevent rot and mould.
