NK MehtaSowing radishes under a tunnel in November feels like a clever way to keep the vegetable patch busy. However, many gardeners lift their first plants a month later and find long leaves with a thin, stringy root. In most cases, the tunnel is not to blame. The real culprit is usually the seed packet, because a radish bred for summer simply does not behave the same way in late autumn.
The good news is that a November sowing can still pay off. With the right variety, a well-managed tunnel and a little patience, you can pull crisp, peppery radishes in the middle of winter.
Why Summer Radishes Struggle Under a Tunnel in November
Summer radishes are bred for warm soil and long, bright days. In those conditions, they race from seed to plate in three to four weeks. November turns that formula upside down. Days are short, light is weak and the soil cools quickly at night, even beneath plastic.
As a result, a summer variety tends to put its energy into leaves rather than roots. Here is what usually goes wrong:
- Weak light: seedlings stretch towards the plastic and become leggy, so the root never swells properly.
- Cold soil: radishes can germinate in cool ground, but growth slows sharply once the soil sits below about 10°C.
- Slow growth: a radish that takes too long often turns woody, hollow or unpleasantly hot.
- Damp air: condensation under the tunnel encourages damping-off, mildew and slugs.
Summer, Forcing and Winter Radishes Compared
Not every radish suits a cold tunnel. In fact, the type you choose matters more than the date you sow. The table below shows how the main groups behave.
| Radish type | Bred for | Result under a tunnel in November | Time to harvest in winter | When to sow |
|---|---|---|---|---|
| Summer radish | Warm soil, long days | Leafy tops, small or hollow roots | Unreliable | Late spring to late summer |
| Forcing (early) radish | Low light, cool conditions | Compact leaves, firm round roots | Roughly 6–10 weeks | Autumn to early spring under cover |
| Winter radish (e.g. Black Spanish Round) | Slow growth into autumn | Too late to start in November | 8–10 weeks from a summer sowing | July to early September |
Choosing the Right Radish Variety for November Sowing
Look for “forcing” on the seed packet
The simplest fix is to pick a forcing radish. These varieties were developed for frames, cold greenhouses and tunnels. They keep their leaves short and still form a round root when light is scarce. Well-known examples include ‘Saxa 2’ and ‘Gaudry’. If a packet mentions sowing “under cover” from autumn to early spring, that is a good sign.
How to sow radishes under a tunnel
Once you have the right seed, the method is straightforward. Even so, a few details make a big difference in cold weather:
- Wait for a mild, dry spell so the soil is workable rather than sticky.
- Close the tunnel for a few days beforehand to warm the ground slightly.
- Sow thinly, about 1 cm deep, in rows 10–15 cm apart.
- Thin seedlings to 3–4 cm apart, because crowded radishes rarely form good roots.
- Water lightly in the morning, so the surface dries before nightfall.
Caring for Radishes Under a Tunnel Through Winter
A tunnel protects radishes from wind and heavy rain. At the same time, it traps moisture, so good care is mostly about balance. Open the ends on mild, sunny days to let damp air escape, then close them again before evening. Keep the plastic clean, since every bit of grime cuts the little light available in December. On nights of hard frost, a layer of horticultural fleece over the rows adds extra protection.
Finally, check the roots regularly. Winter radishes from a forcing variety are best pulled at marble to cherry size. Left too long, even a good variety can split or turn spongy.
Frequently Asked Questions
Can I grow radishes under a tunnel in November?
Yes. Choose a forcing variety, sow thinly and ventilate on mild days. Expect a slower harvest than in summer, usually six to ten weeks.
Why are my November radishes all leaves and no root?
This usually means a summer variety met low light and cold soil. Crowded seedlings and overwatering make the problem worse.
Which radish varieties suit winter sowing under cover?
Forcing radishes such as ‘Saxa 2’ and ‘Gaudry’ are reliable choices. They tolerate short days and keep compact foliage.
Do radishes under a tunnel need watering in winter?
Only lightly. The soil should stay just moist, so water in the morning and only when the surface feels dry.
