Plant Winter Radishes in December and Harvest Them in February!

Key Takeaways: Winter Radish Essentials

• ✅ Timing is Everything: Sow in December for a crisp, spicy February harvest.
• ✅ The Right Variety: Choose dedicated winter types like 'Black Spanish' or 'Mooli'—summer radishes won't thrive now.
• ✅ Protection is Key: You must use a cold frame or greenhouse to keep the soil workable.
• ✅ Water Sparingly: Winter damp kills more plants than the cold; keep ventilation high.
• ✅ Gear Up: A cold frame is the most cost-effective tool for this specific crop.

If you think the vegetable patch goes to sleep in December, think again. In my 12+ years helping UK gardeners at Greenhouse Stores, the biggest myth I encounter is that you have to hang up your trowel once the frost bites.

The truth? You can absolutely plant winter radishes in December. In fact, doing so now sets you up for a brilliant "hungry gap" harvest in February when fresh crunch is hard to find. While summer varieties are quick and mild, winter radishes are the heavyweights of the root world—peppery, robust, and perfectly suited to the UK's cooler climate, provided you give them a little help.

Here is exactly how we do it, ensuring you get a crop rather than just a patch of frozen mud.

Why Grow Winter Radishes Now?

Most gardeners are familiar with the small, red salad radishes (like 'French Breakfast') that take four weeks to grow in spring. Winter radishes are a different beast entirely.

Botanically, they are bred to mature more slowly and withstand lower light levels. They produce much larger roots—sometimes the size of turnips or long carrots—and have a denser texture that stores incredibly well.

The Flavour Profile

The flavour is the real winner here. Winter varieties tend to be punchier and earthier. They are superb in winter stir-frys, roasted alongside Sunday joints, or sliced paper-thin into winter salads for a serious kick.

By planting in December, you are utilising "dead time" in your garden. It’s a fantastic way to keep your soil active and ensures you have fresh produce right when supermarket prices for fresh veg start to climb in late winter.

Essential Equipment: Protecting Your Crop

I'll be honest with you—you cannot simply scatter seeds into soggy, frozen lawn in December and expect a miracle. To succeed with a December sowing, you need to create a microclimate.

The Cold Frame Advantage

For winter radishes, a cold frame is arguably your best friend. These low structures sit close to the ground, warming the soil significantly and protecting seedlings from wind and snow. Because radishes don't grow very tall, a cold frame provides ample height.

Glass or polycarbonate glazing traps the weak winter sun's heat, raising the internal temperature just enough to trigger germination. In our tests, soil inside a cold frame can be 3-5°C warmer than the ground outside—that is the difference between life and death for a seed in December.

Small Greenhouses

If you don't have a cold frame, a small greenhouse is the gold standard. It gives you more control over ventilation (crucial for stopping damp) and allows you to work comfortably out of the rain. If you are growing in a larger greenhouse, you can even use cloches inside the greenhouse for a "double-glazing" effect during particularly harsh freezes in January.

Choosing the Right Variety

This is where most beginners fail. Do not sow 'Cherry Belle' or standard salad radishes now. They will likely bolt or turn woody. You need specific winter cultivars.

Top Picks for UK Winter Growing:

1. Black Spanish (Round or Long): These have a tough, charcoal-coloured skin (which you peel) and snow-white flesh. They are incredibly hardy and have a sharp, horseradish-like kick.
2. China Rose: A beautiful pink-skinned variety. It's slightly milder than the Black Spanish and adds great colour to winter plates.
3. Mooli (Daikon): These long white roots are popular in Asian cooking. They need deep soil (so dig well!), but they are surprisingly resilient to UK winters if kept frost-free.

Step-by-Step: Planting Your December Radishes

We generally tackle this job during the first dry weekend of the month. It fits in perfectly alongside other December gardening jobs like cleaning tools or pruning fruit trees.

1. Prepare the Soil

Winter radishes hate compacted soil. If the ground is hard, the roots will fork or stunt.

• Dig Deep: Fork over the soil to a depth of at least 15cm (6 inches).
• Drainage is King: In winter, wet soil is the enemy. Incorporate some horticultural grit or sharp sand to improve drainage.
• No Fresh Manure: Avoid fresh manure, as the excess nitrogen encourages leaf growth at the expense of the root—and causes forking.

2. Sowing the Seeds

• Spacing: Sow seeds thinly in drills about 1cm deep. Space rows about 15-20cm apart.
• Cover: Cover lightly with soil.
• The Container Option: If your ground is frozen solid, you can grow these in deep containers or planting bags inside your potting shed or greenhouse. Just ensure the pot is at least 20cm deep.

3. Immediate Protection

As soon as seeds are in, close the lid of your cold frame or greenhouse door. If a severe frost is forecast immediately after planting, throw a layer of horticultural fleece over the soil surface for a few days to aid germination.

Winter Care: The "Less is More" Approach

Gardening in winter is less labour-intensive than summer, but it requires more observation.

Watering

You will hardly need to water. In December and January, evaporation rates are low. Check the soil once a week. If it feels dry an inch down, give it a light drink. Overwatering now leads to damping-off disease or rot.

Ventilation

This is critical. On those crisp, sunny winter days where the temperature creeps up, open the vent of your greenhouse or prop open the cold frame lid. Stagnant, damp air encourages grey mould (Botrytis). Fresh air keeps the plants healthy.

Thinning Out

Once seedlings appear (which may take 2-3 weeks in December cold), thin them out. Aim for a spacing of about 10-15cm between plants. Crowded radishes won't bulb up nicely.

The Container Method: No Garden Required

Not everyone has open ground. The beauty of winter radishes is that they thrive in pots, making them perfect for patio gardeners or those with paved courtyards.

Grab a deep container (a recycled florist bucket with holes drilled in the bottom works wonders). Fill it with a mix of general-purpose compost and 20% grit. Place the pot against the wall of your house—bricks release heat absorbed during the day, keeping the pots slightly warmer at night.

If you have a lean-to greenhouse, growing in pots on the shelving is an excellent use of vertical space. For more on maximising small spaces, check out our greenhouse growing guide.

Harvesting: The February Reward

Depending on how cold the winter is, your radishes should be ready to lift from mid-February onwards.

How to Tell They Are Ready

Brush away a little soil from the base of the leaves. You should see the "shoulder" of the root. It should look substantial—roughly golf-ball size for round varieties, or 2-3cm diameter for long varieties.

Lifting

Don't pull them by the leaves; the foliage can snap off in winter. Use a hand fork to gently lever them out of the ground.

Storing

If you can't eat them all at once, lift them anyway before they turn woody. Twist off the foliage (don't cut it, twisting prevents bleeding) and store the roots in a box of damp sand in a cool, dark place (like a shed or garage). They will keep for weeks this way.

Summary

Planting winter radishes in December might seem against the grain, but with the right protection, it's a rewarding project that bridges the gap between seasons. It keeps your green fingers active and rewards you with flavours you simply cannot buy in the average supermarket.

Whether you are using a dedicated cold frame or a small patio greenhouse, the key is protection from the wet and the wind. Give them shelter, and they will give you a harvest.

Happy Growing!