GardenTrack
Join the beta

Biennial Plant · zones 5–10 · 49 varieties

Onion

Allium cepa

Amaryllidaceae — the same plant family as garlic, leek, scallion, shallot and 1 more here. Relatives share pests and diseases, which is why rotation plans group by family.

Onion (Allium cepa) is a biennial plant for USDA zones 5–10. It wants full sun and pH 6–7 soil, with about 1 in of water weekly. It matures in about 85–120 days from sowing. Watch for onion maggot and neck rot. Below: its full sourced profile from 9 extension sources, plus a planting calendar timed to your frost dates.

Zones 5–10 — USDA USDA
Sun Full sun
Water Moderate
Matures 85–120 days — from seed from seed
Mature size 12–18 in
Spacing 3–4 in
Soil pH 6–7
Frost Very hardy
When to plant oniontypical · zone 6b
Your zone
…or your ZIP, for your real frost dates

Establishing
Germinating
Growing
Seedlings
Harvest
Bulbing up
Curing

Typical dates for zone 6b — set your zone or ZIP for yours. This calendar assumes the crop is started indoors. Timing is a guide from the crop's sourced growth stages; confirm with your local frost dates and extension before you sow.

Growing onionevery fact says where it came from

What we will not put a number on

We do not give a feeding rate for this crop, and that is deliberate rather than a gap. The figures published by extension services are pounds of nitrogen per acre for a production field — they do not convert safely to a raised bed or a pot without knowing your soil test and your fertilizer's analysis, and guessing errs toward burning roots. It is also why every chart you find online disagrees with the next one.

We give watering as a depth per week rather than gallons per plant, because that is how it is actually measured and how the published figures are written. A gallons-per-plant number depends on your spacing, your soil and whether the plant is in a pot — so it would look more precise than it is.

Site & soil

Hardiness zones
5–10
Sun
Full sun
Soil pH
6–7
Soil texture
Loam, Sandy, Well drained
Frost tolerance
Very hardy

No published figure for the temperature frost starts to hurt it, the temperature that would kill it and a heat limit. We looked — where a number is missing here it is missing from the research, not skipped. The crop’s frost and heat tolerance above still applies.

The plant

Mature height
12–18 in
Mature spread
6–12 in
Spacing in row
3–4 in
Between rows
12–18 in
Planting depth
1–1.5 in
Support
Self-supportingest
Grown from
Direct sow, Transplant, Sets

There is no line here for a container size and whether it grows fast or slow, because we have no figure to put there. We went looking and wrote down what we read — it is missing on purpose, not because nobody checked.

Water & feeding

Water needs
Moderate
Water per week
1 in/wk
Critical water
Bulbing
Feeding
Heavy

Timing & fruiting

Days to maturity
85–120 days from seed
Start indoors before planting out
8 wk
Harvest cues
Tops falling over, Skin set

There is no line here for how long after the last frost to plant it out and how long before or after the last frost to sow it, because we have no figure to put there. We went looking and wrote down what we read — it is missing on purpose, not because nobody checked.

Planted again for autumn

Sow by
late Jul typical · zone 6b

85 days to maturity from sowing, counted back from the first frost above. Not published for anywhere in particular: it is your own frost date and this crop's own figure, which is why it works wherever you are. A days-to-maturity figure is a catalog number for a good season rather than a promise, and a cold month moves it.

Edible parts per source: bulb, leaf.

What tends to go wrongmost-cited first
PestsOnion maggotThripsBulb mitesAllium leafminer
DiseasesNeck rotFusarium basal rotPink rootBacterial soft rotWhite rot

Compiled from the extensions cited below. Which ones actually show up depends on your region — your extension's local list is the last word.

Companionswhat to plant near onion
✓
CarrotsTrialed

Interplanted onions confused carrot rust fly in some trials and did nothing in others. Worth a try, not a bet.

✓
BeetsTraditional

Chart canon, both directions.

✓
Cabbage familyTraditional

Old chart pairing; both hold cool-season beds.

✓
LettuceTraditional

On the classic charts — lettuce's own row lists onions.

✓
TomatoTraditional

Chart canon says onions and garlic make good tomato neighbors. No trials to point at, no conflict either.

✕
BeansTraditional

The most consistent 'no' in companion planting. Unproven, unanimous.

✕
PeasTraditional

Same flag as beans — every chart agrees.

Companion pairings from university extensions; badge = how strong the evidence is.

⚠ Reported toxicityverbatim from cited sources

Different parts differ — the edible part is the bulb and leaf; the notes below flag other parts or preparations.

PeopleHemolytic anemia

Petsdogs, cats, horses

Recorded exactly as the source states it — not medical or veterinary advice. If a person or animal may have eaten a toxic part, call Poison Control (1-800-222-1222) or your vet / the ASPCA line (888-426-4435).

Featured varieties49 with their own page
Ailsa Craig Long Day · 110d Avalon Intermediate Day · 85–120d Blush Intermediate Day · 85–120d Borettana Cipollini Cipollini · 105d Caliber Long Day · 85–120d Candy Intermediate Day · 110d Clear Dawn Long Day · 104d Cortland Long Day · 110d Crystal White Wax Short Day · 70d Dakota Tears Long Day · 112d Evergreen Hardy White Bunching Bunching · 65d Expression Long Day · 98d Flat of Italy Cipollini Cipollini · 70d Frontier Intermediate Day · 100d Gladstone Intermediate Day · 110d Gold Coin Cipollini Cipollini · 80d Merlin Short Day · 85–120d New York Early Long Day · 98d Patterson Long Day · 104d Purple Haze Long Day · 85–120d Purplette Long Day · 60d Red Amposta Intermediate Day · 115d Red Baron Long Day · 85–120d Red Bull Long Day · 118d Red Burgundy Short Day · 100d Red Creole Short Day · 110d Red Grano Short Day · 100–120d Red Mountain Long Day · 107d Red Rock Short Day · 85–120d Red Wethersfield Long Day · 110d Redwing Long Day · 118d Rossa di Milano Long Day · 114d Rossa Lunga di Tropea Long Day · 110d Ruby Long Day · 90–100d Scout Intermediate Day · 85–120d Sierra Blanca Intermediate Day · 109d Southport Red Globe Long Day · 110d Stuttgarter Long Day · 85–120d Talon Long Day · 110d Tannat Long Day · 110d Texas 1015Y SuperSweet Short Day · 110d Texas Early Grano Short Day · 110d Tokyo Long White Bunching Bunching · 65d Walla Walla Long Day · 100–125d White Sweet Spanish Long Day · 110d White Wing Long Day · 97d Yellow Granex PRR Short Day · 110–160d Yellow Sweet Spanish Long Day · 110–130d Yosemite Intermediate Day · 85–120d

Open one and add it to your garden — it lights up here. The rest of the 49 are in the full list below.

All 49 varietiesthe ones with their own page are linked
Variety Type DaysColorWhat it is known for
Ailsa Craig Heirloom Long Day 110 Yellow
Avalon F1 Intermediate Day 85–120 Yellow
Blush Intermediate Day 85–120 Red
Borettana Cipollini Heirloom Cipollini 105 Yellow Fedco Seeds describes this askeeps a long time after picking
Caliber F1 Long Day 85–120 Yellow Urban Farmer Seeds describes this askeeps a long time after picking
Candy F1 Intermediate Day 110 Yellow
Clear Dawn Long Day 104 Yellow Fedco Seeds describes this askeeps a long time after picking
Cortland F1 Long Day 110 Yellow Territorial Seed describes this askeeps a long time after picking
Crystal White Wax Heirloom Short Day 70 White
Dakota Tears Long Day 112 Yellow Fedco Seeds describes this askeeps a long time after picking
Evergreen Hardy White Bunching Heirloom Bunching 65 White Johnny's Selected Seeds describes this astakes the cold
Expression F1 Long Day 98 Yellow Fedco Seeds describes this askeeps a long time after picking
Flat of Italy Cipollini Heirloom Cipollini 70 Red
Frontier F1 Intermediate Day 100 Yellow Johnny's Selected Seeds describes this askeeps a long time after picking
Gladstone F1 Intermediate Day 110 White
Gold Coin Cipollini Cipollini 80 Yellow
Merlin F1 Short Day 85–120 Yellow
New York Early Long Day 98 Yellow Fedco Seeds describes this askeeps a long time after picking
Patterson F1 Long Day 104 Yellow Fedco Seeds describes this askeeps a long time after picking
Purple Haze F1 Long Day 85–120 Red
Purplette Long Day 60 Purple Johnny's Selected Seeds describes this askeeps a long time after picking
Red Amposta Heirloom Intermediate Day 115 Red
Red Baron Long Day 85–120 Red
Red Bull F1 Long Day 118 Red Fedco Seeds describes this askeeps a long time after picking
Red Burgundy Heirloom Short Day 100 Red
Red Creole Heirloom Short Day 110 Red Dixondale Farms describes this askeeps a long time after picking
Red Grano Short Day 100–120 Red
Red Mountain F1 Long Day 107 Red Fedco Seeds describes this askeeps a long time after picking
Red Rock F1 Short Day 85–120 Red Urban Farmer Seeds describes this askeeps a long time after picking
Red Wethersfield Heirloom Long Day 110 Red Fedco Seeds describes this askeeps a long time after picking
Redwing F1 Long Day 118 Red Johnny's Selected Seeds describes this askeeps a long time after picking
Rossa di Milano Heirloom Long Day 114 Red Fedco Seeds describes this askeeps a long time after picking
Rossa Lunga di Tropea Heirloom Long Day 110 Red
Ruby Heirloom Long Day 90–100 Red
Scout F1 Intermediate Day 85–120 Yellow
Sierra Blanca F1 Intermediate Day 109 White
Southport Red Globe Heirloom Long Day 110 Red Fedco Seeds describes this askeeps a long time after picking
Stuttgarter Heirloom Long Day 85–120 Yellow Urban Farmer Seeds describes this askeeps a long time after picking
Talon F1 Long Day 110 Yellow Fedco Seeds describes this askeeps a long time after picking
Tannat F1 Long Day 110 Red Fedco Seeds describes this askeeps a long time after picking
Texas 1015Y SuperSweet Heirloom Short Day 110 Yellow
Texas Early Grano Heirloom Short Day 110 Yellow
Tokyo Long White Bunching Heirloom Bunching 65 White Botanical Interests describes this astakes the heat
Walla Walla Heirloom Long Day 100–125 Yellow
White Sweet Spanish Heirloom Long Day 110 White Pinetree Garden Seeds describes this askeeps a long time after picking
White Wing F1 Long Day 97 White Fedco Seeds describes this askeeps a long time after picking
Yellow Granex PRR F1 Short Day 110–160 Yellow
Yellow Sweet Spanish Heirloom Long Day 110–130 Yellow
Yosemite Intermediate Day 85–120 Yellow Urban Farmer Seeds describes this askeeps a long time after picking
Sources9 cited · 8 organizations
  • ASPCA Animal Poison Control Center
  • Clemson Cooperative Extension, Home & Garden Information Center
  • NC State Extension
  • Onion ipmPIPE Diagnostic Pocket Series — H. F. Schwartz (Colorado State University) and C. S. Cramer (New Mexico State University), hosted by Washington State University
  • University of Illinois Extension
  • University of Maryland Extension
  • University of Minnesota Extension
  • Utah State University Extension

We compile bare facts from these university-extension and horticultural sources, never copied prose. 18 of the 19 values on this page carry a citation. The rest are marked est; hover one and it says why — either nobody publishes a figure we could point at, or a person set it and attached no source. Figures vary with climate and seed source; confirm with your local extension before you buy.

Growing more than onion? Browse all crops, or grab the spacing calculator and frost date lookup. The GardenTrack app (now in beta) remembers what you planted and where, then tells you what to do and when. Join the beta →