Onion Growing Guide
Growing Onion is easier than you think. This guide walks you through everything you need — from planting your first seed to harvesting.
At a Glance
Difficulty
Easy
Category
Vegetable
Sun Exposure
Full Sun
Frost Tolerance
Frost Hardy
Cold Hardiness
Survives to -12°C
Plant Family
Amaryllidaceae
Growing Season
Cool Season
Plant Lifecycle
Biennial
Also grows well as
How to Start It
★ Recommended for beginners
Press sets pointy-end up about 2 cm deep and 10 cm apart in early spring, just the tip showing. Nearly foolproof and quick to bulb.
Sets are easiest and fastest; seed gives more variety and bigger bulbs but needs an early indoor start. Match the variety to your latitude (long-day onions for the north, short-day for the south) or you'll get tiny bulbs.
When To Start
First Chance to Plant
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Last Chance to Plant
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When should you plant Onion?
Your planting dates depend on your local climate. Sign up and add your location to unlock personalized dates.
Your Onion Planting Window
Start planting
May 15, 2026
Last chance
Sep 10, 2026
The Journey Ahead
Onion's Lifecycle
Seedling
Mature Plant
Seed Production
Step 2
Planting & Sprouting
Expect sprouts in 7–14 days
Growing Tips
- 1Onions are shallow-rooted, so keep them weed-free and evenly watered, and stop watering once the tops start to fall.
- 2Don't bury the shoulders — onions like to sit with their tops at the surface.
Seedling Phase
Step 3
Growth & Maturity
~110
Days to Maturity
45 cm
Mature Height
10 cm
Mature Width
Pests to Watch For
Diseases to Watch For
Mature Plant
Step 4
Harvesting
Harvest Window
14 days
When to Pick
Harvest when the tops yellow and flop over in mid–late summer
How to Harvest
- 1When most of the tops have flopped and yellowed, ease the bulbs up and lay them on the soil for a day or two.
- 2Then cure them in a dry, airy, shaded spot for 2–3 weeks before storing.
Step 5
Saving Seeds
How to Save Seeds
Onions are biennial — replant a bulb the next spring, let it flower into a round seed head, and collect the black seed once it dries. Keep one variety to seed at a time to avoid crossing.
Seed Production
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