Radishes are one of the quickest vegetables you can grow. For an ordinary crisp salad radish, sow seeds directly into moist soil, leave a little space between seedlings and start checking the roots after about four weeks. Small, repeated sowings are far more useful than emptying a whole packet into one row, because young radishes are at their best before they become oversized or woody.
There is more than one type of radish, however. The little round red roots in supermarket salads are not grown or harvested in exactly the same way as large winter radishes. Choose the right type and you'll avoid much of the confusion about when to sow, how far apart to space them and how long to wait.
Salad radishes or winter radishes?
Most people starting out mean salad radishes: small round or cylindrical roots, often red on the outside and white in the middle. Some are pink, purple, white or multicoloured. These are quick crops suited to spring and other relatively cool periods.
Winter radishes include longer white and darker-skinned varieties grown for larger roots, sometimes for cooking or pickling. They generally need more space and more time than a tiny salad radish.
Read the packet rather than relying only on the photograph. A winter radish sown and picked after four weeks may hardly have started developing its intended root, while a small salad type left in the ground for months is likely to become poor eating.
If this is your first attempt, buy an ordinary salad radish variety. You'll see results quickly and can make adjustments to spacing and watering without waiting an entire season.
Where radishes grow best
Choose an open, reasonably sunny position with fertile, well-drained soil. In particularly warm weather, some light shade in the hottest part of the day can be useful, because salad radishes may bolt—send up a flower stalk—when stressed by heat and drought.
Radishes don't need a deeply dug bed with elaborate feeding. Remove weeds, break up clods and rake the top layer to a relatively fine texture so tiny seeds can establish. Avoid leaving large stones or lumps where the swelling roots need room to expand.
A small raised bed, an allotment row or even a suitably deep patio trough can work. For a short salad crop, you can sow where an earlier vegetable has finished or in a space that will later be needed for a larger summer plant.
Don't crowd radishes beneath an established crop that blocks all the light. They grow quickly, but still need enough sunshine and moisture to form crisp roots.
When to sow radishes in Britain
The Royal Horticultural Society recommends sowing salad radishes during spring, early summer and late summer, avoiding spells of very hot, dry weather. You can start particularly early under suitable protection if the soil has warmed enough for germination.
A spring sowing is often easier than a mid-summer sowing because the weather is cooler and the compost or soil is less likely to dry suddenly. Later in summer, choosing a position with some light shade may give better results.
Instead of sowing a metre-long row every time, work out how many radishes your household actually eats in one or two weeks. Make a small sowing, then another one a week or two later. The aim is to keep young roots coming rather than produce fifty ready-to-eat radishes on the same afternoon.
Winter radishes follow a different pattern. The RHS recommends sowing suitable types in July or August, giving them enough time to produce large roots before the colder season.
How to sow salad radishes
- Prepare a shallow seed drill. Make a small furrow around 1cm deep in fine, moist soil.
- Water the drill first if the ground is dry, allowing the moisture to soak in before scattering the seeds.
- Sow thinly, aiming for seeds roughly 2.5–5cm apart where practical.
- Leave room between rows. The RHS recommends approximately 15cm for salad radishes, enough to weed and harvest without stepping on neighbouring plants.
- Cover the seeds lightly with soil and settle the surface with your hand or the back of a rake.
- Mark the row so it won't be disturbed while seeds germinate.
- Keep the seedbed moist until seedlings establish, particularly after an unusually dry spell.
Young radish seedlings usually develop quickly in suitable conditions. If the row comes up in an almost solid line, thin it promptly; roots cannot swell properly when dozens of plants share the same few centimetres.
You can sow radishes between slower-growing vegetables where there is enough light and water, but make sure you can harvest them without damaging the main crop's roots.
Growing radishes in containers
A patio trough or growing box is ideal for small batches of salad radishes, as long as the container has drainage holes and enough depth for the variety. Use fresh peat-free multi-purpose compost and position it in a bright place.
Fill the container, leave space for watering, then sow directly into the compost. Avoid raising seedlings indoors to transplant later. Radishes make taproots early, and moving them is unnecessary for such a short-season crop.
Container compost can dry much more quickly than an open vegetable bed. Check moisture frequently, especially during warm spells. A tiny trough left in full afternoon sun can go from comfortable to extremely dry faster than you might expect.
Use the same principle of staggered sowing in a container. A narrow strip sown every week or two may supply a more useful stream of fresh radishes than a densely planted box all maturing at once.
How to look after the seedlings
The main tasks are keeping weeds out, preventing the soil from drying hard and giving each root enough space. Radishes are fast, so the period of routine care is shorter than for most vegetables.
Inspect the seedlings once they have formed their first proper leaves. Where you sowed more thickly than intended, thin carefully so neighbouring plants have room to swell. Don't wait until the roots have already distorted one another.
Water when necessary to maintain reasonably even moisture. Radishes that suffer prolonged dryness can become unpleasantly hot or woody, and they may bolt rather than producing the crisp roots you wanted.
Keep the row weeded by hand close to the roots. A hoe can work between rows but is easy to use too aggressively near small radish plants. If flea beetles leave small holes in young foliage, check the scale of damage. The RHS notes that fine mesh can help protect brassica seedlings from insects.
Sowing winter radishes correctly
Winter radishes are a different crop, with larger roots and a longer growing period. The RHS recommends sowing them in July or August, usually around 2cm deep, and spacing plants approximately 15–20cm apart depending on the variety.
This extra spacing is important. A daikon or other large winter root cannot develop into its expected shape if planted at the same tight spacing as a small salad radish.
Use reasonably fertile, stone-free ground and keep the rows free from weeds during establishment. Check the variety's expected mature size and harvest time. Some are eaten raw after slicing or grating; others are particularly useful in cooked dishes and pickles.
Don't assume a large winter radish is spoiled because it has a stronger flavour than a mild spring salad radish. These are different crops intended for different uses.
When and how to harvest salad radishes
Many salad radishes are ready within four to six weeks, depending on variety and weather. Begin checking once the shoulders of the roots have reached a useful size. You can carefully loosen the soil around one root rather than pulling the whole row to inspect it.
Pick young and often. Leaving salad radishes for too long can produce roots that are hollow, fibrous, peppery or unpleasantly woody. Unlike a storage carrot, an ordinary salad radish is usually better harvested promptly once ready.
Lift by holding the leaves near the root and pulling steadily; if the soil is hard, loosen it gently first. Wash away soil before bringing the crop into the kitchen.
Remove the tops for storage if you won't use the radishes immediately, because attached leaves can draw moisture from the root. Use tender, clean leaves in suitable recipes if you enjoy them, and discard any unhealthy foliage.
What can go wrong with radishes?
Plenty of leaves but no proper roots: Excessive crowding, too much shade or unsuitable growing conditions may have prevented swelling. Check spacing and light before blaming the seed.
Hot, woody or hollow roots: The plants may have been left too long or stressed by heat and dryness. Choose a cooler growing period and harvest sooner next time.
Seedlings disappear: Inspect for slugs and snails, particularly in damp weather. Protect the young row and remove shelters where pests are hiding.
Plants flower before producing useful roots: This is called bolting. Hot, dry weather and seasonal stress can encourage it. Try another sowing at a cooler time rather than waiting for the flowering plant to make a normal crisp radish.
Roots crack or split: Abrupt changes in moisture can contribute. Aim for steadier watering, especially in containers where compost dries quickly.
Common questions
Can you grow radishes all summer?
Yes, but not every sowing will perform equally well during very hot weather. The RHS recommends avoiding hot, dry spells and using a cooler site with some midday shade for summer sowings.
Do radishes need fertiliser?
Usually not if they are growing in reasonably fertile garden soil or fresh container compost. Focus on the right sowing time, spacing and watering before adding feed.
Are radish leaves edible?
Young, healthy radish leaves can be used in cooking. Wash them carefully and avoid eating foliage that has been treated with products not intended for edible leaves.
Sources and further reading
- Royal Horticultural Society — How to grow radishes. Salad and winter sowing depths, spacing, harvesting and care.