Onion
cool-season crop
At a glance
| Suitable zone groups | All four zone groups (3-4, 5-6, 7-8, 9-10), as a cool-season annual |
|---|---|
| Planting window | See the guide text below, in general terms relative to your last spring frost |
| Sun | Full sun |
| Soil | Loose, well-draining soil free of heavy clay |
| Watering | Consistent, regular watering |
About this plant
Onions are a reliable staple crop suited for gardens in all zones when grown as an annual. Plant sets or young transplants in early spring as soon as the ground is workable, taking advantage of their cool-season frost tolerance. Onions require full sun and loose, well-draining soil free of heavy clay or rocks.
Because onions have shallow root systems, they require consistent, regular moisture and diligent weeding so they do not face competition. Stop watering when the top foliage begins to turn yellow and flop over to allow the bulbs to mature and cure properly.
Common beginner failures and fixes
- Small or stunted bulbs: Weed frequently to eliminate root competition and keep soil loose.
- Premature bolting: Avoid planting too early in extreme cold and keep watering consistent.
- Rotted bulbs: Plant in raised beds or sandy, well-draining soil to prevent waterlogging.
- Foliage yellowing early: Ensure uniform watering and avoid underwatering during dry spells.
Beginner checklist
- Select a sunny garden bed with loose, well-draining soil.
- Clear the planting area of all weeds and large rocks.
- Plant sets or transplants in early spring.
- Keep the shallow root zone consistently moist with regular watering.
- Allow foliage to fall over and dry before harvesting mature bulbs.
Zone groups and planting windows here are general guidance. Confirm your own zone and last frost date locally before planting.