Yellow onions are the workhorse of the Zone 2 vegetable garden: the best-storing onion you can grow, the one you will still be cooking with in midwinter. They are hardy, undemanding, and — provided you choose long-day varieties — perfectly matched to northern summers, where days stretch to 14 to 16 hours. If you grow only one onion in Zone 2, make it a yellow storage onion.
This guide covers when to plant yellow onions zone 2 — the sowing and transplanting dates that work in Zone 2, and the soil, spacing, sun, water and care the crop needs. All frost dates below are USDA/NOAA zone averages for Zone 2, not promises for any one garden — check your local extension service, because frost dates vary by microclimate, elevation and year.
Zone 2 at a glance
USDA Zone 2 has average winter lows of −50 to −40°F, an average last spring frost of June 1–15 and an average first autumn frost of August 15–September 1, leaving roughly 60 to 90 frost-free days in an average year. That is one of the shortest growing seasons in the United States, so short-season varieties, indoor starting where the crop allows it, and protection at both ends of the season — a cold frame, cloche or low tunnel — are often the difference between a harvest and an empty bed.
| Detail | Zone 2 guidance |
|---|---|
| Average last spring frost | Jun 1–15 (average/range) |
| Average first autumn frost | Aug 15–Sep 1 (average/range) |
| Frost-free window | Roughly 60–90 days |
| Days to germination | 7–14 days |
| Days to maturity | 90–120 days |
| Sowing | Indoors April 20 to May 18, or direct sow at last frost |
| Transplanting | After last frost (Jun 1–15) |
| Harvest | Around September 6 to October 6 |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 4–6 inches |
| Water needs | moderate |
When to plant yellow onions in Zone 2
You have two routes in Zone 2: start seeds indoors April 20 to May 18 for a head start, or sow directly around the average last frost of June 1–15. Either way, with 90–120 days to maturity the harvest falls around September 6 to October 6, before the average first frost of August 15 to September 1. Frost dates are zone averages — check your local extension service.
The planting calendar hub gives the Zone 2 picture month by month — see June in Zone 2 and July in Zone 2 — and the frost date calculator and seed starting calculator turn your frost averages into sowing dates.
Starting yellow onions in Zone 2
Plant sets in mid to late May, a couple of weeks before the average last frost, with the tip just showing above the soil. From seed, start indoors 8 to 10 weeks before the last frost and transplant the seedlings out in late May, when they are about pencil thick. Keep the bed weed-free — onions compete poorly with weeds — and water evenly while the bulbs are swelling.
In Zone 2, a raised bed warms earlier than flat ground, and black plastic laid over the bed for a week or two before planting warms the soil further. Harden off indoor-started plants for a week to ten days before they go outside, putting them out for a few hours a day in a sheltered spot and bringing them in if frost is forecast.
Soil, spacing, sun and water
Yellow Onions grows best in full sun, in soil with a pH of 6.0–7.0. Test your soil through your local extension service rather than guessing, and dig in well-rotted compost before planting to improve drainage and moisture holding. Space plants 4–6 inches apart — in a short season it is tempting to crowd plants in, but crowded plants stay small and invite disease, so use the plant spacing calculator if you are laying out a bed. Yellow Onions needs moderate water: water deeply and less often rather than lightly every day, water at the base in the morning so leaves dry before night, and mulch to keep the soil evenly moist. Check the soil a finger's depth down and water when it feels dry there.
Companion planting
Good companions for yellow onions include marigolds, basil, onions, lettuce. The companion planting finder can suggest combinations for your whole bed. Avoid planting yellow onions where the same family (Amaryllidaceae) grew last year, and rotate crops each year to reduce soil-borne disease.
Pests and problems
The common pests and problems to watch for with yellow onions are aphids, slugs, cutworms. Inspect plants regularly, especially the undersides of leaves, and act early: hand-pick larger pests, wash aphids off with a strong jet of water, and remove badly affected leaves rather than waiting for the problem to spread. Healthy plants in the right soil and spacing resist pests better than stressed ones.
Harvest and storage
Lift yellow onions when the tops have flopped over and yellowed, usually 90 to 120 days after planting. Stop watering once the tops begin to fall, lift on a dry day, and cure for two to three weeks in a warm, airy, shaded place until the necks are completely dry and papery. Well-cured yellow onions keep for months in a cool, dry, dark place with good air flow — braid them, or store them loose in a mesh bag, and check them every few weeks for soft bulbs.
Related guides in this series: Red Onions in Zone 2 and Onions in Zone 1 — plus the planting calendar hub for the full Zone 2 year.
Frequently asked questions
When to plant yellow onions zone 2?
Start indoors April 20 to May 18 or sow directly around the last frost (June 1–15), for a harvest around September 6 to October 6. These are zone averages — check your local extension service, because frost dates vary by microclimate and year.
Can I grow yellow onions outdoors in Zone 2?
Yes, with the right variety and timing. The frost-free window is roughly 60 to 90 days, so choose short-season varieties and start indoors where the crop allows it. Yellow Onions is hardy, so it handles cool weather, but still needs protection from hard frosts.
How long does yellow onions take to grow in Zone 2?
Seeds germinate in 7–14 days, and the crop takes 90–120 days to maturity. In Zone 2, cool soil and cold nights can slow growth, so allow the longer end of the range.
What soil and spacing does yellow onions need in Zone 2?
Yellow Onions needs full sun and soil pH 6.0–7.0, spaced 4–6 inches apart. Dig in well-rotted compost, water deeply, mulch, and test your soil through your local extension service.
What pests affect yellow onions in Zone 2?
The main ones are aphids, slugs, cutworms. Inspect plants regularly and act early, but remember that in Zone 2, cold and wind are usually as big a threat as pests, so keep frost protection ready and choose a sheltered spot.