White onions are the mild, crisp onions for fresh eating — sliced raw into salads and salsas, grilled, or pickled whole. They are sweeter and less pungent than yellow onions, which is exactly why they do not store as long, so the plan in Zone 8 is to grow them well, harvest in early summer, and enjoy them fresh. This guide covers when to plant white onions in Zone 8, how to get full-sized bulbs, and how to handle the harvest.
Zone 8 at a glance
Zone 8 covers parts of the southern United States, the Pacific Northwest coast and parts of California, where average winter lows run 10 to 20°F. The average last spring frost falls Mar 1–15 and the average first autumn frost Nov 15–Dec 1. Those are USDA zone averages drawn from NOAA frost records, not exact dates for any one garden — frost dates vary by microclimate, elevation and year, so always check your local extension service and the forecast before planting. Use the frost date calculator for your own averages, and browse the planting calendar hub for the full Zone 8 year.
When to plant white onions in Zone 8
| Step | Timing in Zone 8 |
|---|---|
| Start indoors | January, 8 to 10 weeks before transplanting |
| Transplant outdoors | February to March, once soil can be worked |
| Plant sets outdoors | February to March |
| Autumn sowing (mild spots) | October to November, for overwintering |
| Harvest | June to July, when tops fall over |
White onions are hardy and can go out before the average last frost of Mar 1–15, but they still need to be in early: onions form bulbs in response to lengthening days, and a plant that is still small when the days get long will never catch up. February to March planting, as shown in the Zone 8 February guide, is the window that gives full-sized bulbs. Use the seed starting calculator to work out dates for your own garden.
How to start white onions
Start seed indoors in January in trays, sowing thinly and keeping the compost damp until germination in 7–14 days. Seedlings grown under strong light stay stocky; if they stretch, trim the tops to about 4 inches. Harden off for a week before moving them out in February to March. Sets are the quick route: push them into the soil so the tip just shows, and they will be growing within days in Zone 8's mild late winter.
Soil, spacing and sun
White onions want full sun and a loose, fertile, free-draining bed — on heavy clay, use a raised bed forked through with compost, because wet soil rots bulbs. Soil pH of 6.0–7.0 suits them. Plant shallowly, with the bulb at the surface, and space plants 4–6 inches apart in rows a foot apart. Weed little and often: onions have shallow roots and lose badly to competition, so a clean bed is half the battle.
| Fact | Range |
|---|---|
| Sun | full sun |
| Days to germination | 7–14 |
| Days to maturity | 90–120 |
| Spacing | 4–6 in |
| Soil pH | 6.0–7.0 |
| Sowing method | both |
| Cold tolerance | hardy |
All figures are broad published ranges from standard horticultural references, and they vary by variety, soil and weather. Check your local extension service for advice on your own garden.
Watering and feeding
Water needs are moderate. Keep the bed evenly moist through spring while bulbs are swelling — deep watering once or twice a week beats a daily sprinkle. Stop watering once the tops yellow and flop, so the bulbs dry and cure properly. Mulch with straw in spring to hold moisture, then pull it back from the necks before harvest.
Companion planting
Marigolds, basil and lettuce make good neighbours, fitting around onions without shading them or fighting for the same root space. Onions also help their neighbours: their scent confuses carrot rust fly, so plant a row alongside carrots. Keep onions away from peas and beans, which grow poorly next to alliums. The companions listed for white onions in standard references are marigolds, basil, onions, lettuce.
Pests and problems
Watch for aphids on the foliage, slugs in damp weather and cutworms cutting young plants at ground level. Wash small aphid colonies off with water, fit card collars around transplants against cutworms, and keep the bed tidy to deny slugs hiding places. White rot is the serious soil disease of onions — if it has appeared before, grow onions in fresh ground or containers. The pests most often listed for white onions are aphids, slugs, cutworms. Inspect plants weekly, act early while numbers are small, and encourage natural predators such as ladybirds and hoverflies.
Harvest and storage
Lift when the tops have yellowed and fallen over, usually June to July. Use a fork on a dry day and lay the bulbs in the sun for a week or two to cure, turning once, until the necks feel dry and papery. Trim tops to about an inch and store in a cool, dry, airy place in a mesh bag. White onions are best eaten fresh and keep for a shorter time than yellow onions, so plan to use them through summer and early autumn.
Frequently asked questions
When should I plant white onions in Zone 8?
Plant sets or transplant seedlings in February to March, before the average last frost of Mar 1–15. In the mildest areas, an October to November sowing can overwinter. Planting early is what gives you full-sized bulbs.
Do white onions store well?
Not as well as yellow onions — their mild, juicy flesh is made for fresh eating. Cure them properly and keep them cool, dry and airy, and expect a few months at most. Eat damaged or thick-necked bulbs first.
Why did my white onions bolt?
Bolting — sending up a flower stalk — usually follows a cold snap after warm growth, or stress. Plant at the right time, keep plants watered in spring, and pull any bolted onions promptly to eat, since they will not store.
Can I grow white onions in containers?
Yes, in a deep pot or trough of free-draining compost, spaced 4–6 inches apart. Containers dry out faster, so water more often, and choose a sunny spot. It is a good option if your soil has had onion white rot.
For the full year, browse the planting calendar hub. Compare with White Onions in Zone 7, and see also Yellow Onions in Zone 8.