Onion

Onion

Allium cepa

Plant out 4 weeks before your last spring frost. Space plants 4 in (10 cm) apart.

Photo: Acabashi, CC BY-SA 4.0 · source

When to plant

Timed from your frost dates, so it holds wherever you garden. Give yours and every step below becomes a date.

See the dates for your garden

Enter your average last spring frost and first fall frost. Every timing on this site turns into a calendar date. Not sure of yours? Your local extension service or a search for “last frost date” and your town will tell you; the app finds them from your location.

Last spring frost
First fall frost

Saved in this browser only. Nothing is sent anywhere.

Optimal Transplant - Spring

From bulbsRecommended from bulbs
  1. Plant out4 weeks before your last spring frost
  2. First harvestabout 100 days after planting out

Optimal Fall Planting (Overwinter Sets)

From bulbs
  1. Plant out11 days after your first fall frost
  2. First harvestabout 75 days after next spring's last frost

Optimal Indoor Start

From seedRecommended from seed
  1. Start indoors13 weeks before your last spring frost
  2. Begin hardening off5 weeks before your last spring frost
  3. Plant out4 weeks before your last spring frost
  4. First harvestabout 100 days after planting out

Optimal Transplant

From seed
  1. Plant out4 weeks before your last spring frost
  2. First harvestabout 100 days after planting out

Growing onion

Spacing in the row
4 in (10 cm)
Between rows
12 in (30 cm)
Planting depth
0.5 inches
Sun
Full Sun
Soil
Well-drained, loose, fertile loam
Germination
7-14 days at 50-75°F
Harvest season
Late Summer to Early Fall
Mature height
12-24 inches
Life cycle
Biennial

Sow thinly 0.5 inches deep, firm soil gently.

Watering. Consistent moisture is critical, especially during bulb formation. Avoid overwatering to prevent rot.

Neighbours

The companion chart →

Grows well beside

Keep apart from

Feeding

Seedlings
Apply a dilute balanced liquid fertilizer after true leaves emerge.
Growing
Utilize a balanced liquid or slow-release granular fertilizer during active foliage and early bulb growth.
How often
Every 2-4 weeks during active growth.
Note
Cease high-nitrogen fertilization as bulbs begin to swell to promote bulb rather than foliage growth.

Your onion, planned to the day.

Canopy turns these timings into dates from your own frost data, places every plant at its spacing on your garden map, and tracks it all the way to harvest.

Add onion to your planting calendar →

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