Onion Planting Zones: Best Times and Tips for UK Gardeners

When you're growing onions, a hardy bulb vegetable that thrives in cool to mild climates and is sensitive to day length. Also known as bulb onions, they're one of the most reliable crops for UK gardens if planted at the right time and in the right spot. Unlike some plants that just need sun and water, onions need the right planting zones—not the USDA kind, but the real-world UK version shaped by frost dates, soil warmth, and daylight hours. In southern England, you can get away with planting in late winter. In Scotland or northern Wales, waiting until early spring makes all the difference. Get this wrong, and your onions might bolt or stay tiny.

Soil type matters just as much as timing. Onions hate waterlogged ground. If your soil stays soggy after rain, you need to raise the bed or mix in sand and compost. They also need good sun—six to eight hours a day—and don’t do well in heavy clay. The soil preparation, the process of loosening, enriching, and draining soil before planting to support root development you do before planting onions can make or break your crop. And while many think onions are low-maintenance, they actually need consistent moisture, especially when bulbs start forming. Too dry? Stunted bulbs. Too wet? Rot sets in. It’s a balance.

Day length is another hidden factor. Onions are either short-day, intermediate-day, or long-day varieties. The UK’s long summer days mean you need long-day types like 'Stuttgarter' or 'Copra'—short-day ones won’t bulb up properly here. If you buy seeds or sets without checking the type, you’re guessing. And don’t forget about weed control, the practice of preventing unwanted plants from competing with crops for nutrients, water, and light. Onions have shallow roots and can’t fight back against weeds. A thick layer of mulch or landscape fabric keeps weeds down without choking the plants.

You’ll find plenty of advice online about planting onions in moon phases or using eggshells for fertilizer—but the real wins come from timing, soil, and variety. The posts below give you no-nonsense, UK-tested tips: when to plant in your region, how to pick the right sets, what to do if your onions start flowering early, and how to store them after harvest. No fluff. Just what works in British soil, British weather, and British gardens.