Como cultivar rabanetes a partir de semente (Raphanus sativus)

Radishes are the crop everyone recommends to beginners and almost nobody grows well. Four weeks from packet to plate sounds foolproof, and yet the usual result is a handsome rosette of leaves sitting on top of a thin, woody, fiery little root. The seed is almost never at fault. Radishes are simply so fast that every mistake is compressed into three weeks and ends up written in the root — sow them in the wrong month, too deep, too thickly or too dry and there is no time for the plant to recover. Get four things right and Raphanus sativus really is the easiest vegetable in the garden. This guide covers both radish crops, why late summer is the kindest sowing window of the year, and how to read a bad root when you pull one.

• Botanical name Raphanus sativus — fast annual root crop, Brassicaceae (cabbage family)
• Sow salad radish March–late September outdoors, easiest of all from late August; winter radish July–mid August
• Harvest salad radish 20–30 days; winter radish 8–10 weeks
• Position open sun, stone-free soil that never dries out — light shade is fine in high summer

Why grow radishes

Speed comes first. Twenty to thirty days from sowing to pulling is quicker than any other outdoor root crop, which makes radish the obvious filler for ground just cleared of beans, garlic or early potatoes, and the one vegetable reliable enough to keep an impatient child interested in a garden. It asks for almost no room either: a window box 15 cm deep will give you a respectable picking.

The second reason is range. A single species covers the crisp scarlet globes of Cherry Belle, the blunt red-and-white cylinders of French Breakfast, and — at the far end — mooli, China Rose and Black Spanish winter radishes the size of a forearm that keep in a box of sand until March. Browse the whole family under radish, or by botanical name at Raphanus sativus. New to vegetables from seed? Our beginner's guide to growing vegetables from seed covers the groundwork, and the vegetable sowing calendar sets radish alongside everything else in the plot.

When to sow radishes — and why late summer is the easy window

Radish is a long-day plant, and that single fact explains most disappointing crops. Once day length passes roughly fifteen hours the plant stops investing in its root and starts building a flower spike; heat above about 25 °C flips the same switch faster. A packet sown in mid-June is therefore fighting the plant's own biology — you are asking it to swell at precisely the moment it has decided to bolt.

Sow from late August and every signal runs your way instead. Days are shortening rather than lengthening, nights are cooling, the soil is still warm enough for germination in three or four days, and flea beetle numbers are well past their peak. The roots swell slowly and evenly, which is exactly what makes them sweet and solid rather than hot and pithy. Salad radish can go in outdoors until about the third week of September, and later still under a cloche or cold frame — see our guide to extending the growing season. Winter radish is the exception: it needs a long run, so sow it in July or the first half of August. For everything else that can still go in now, see what to sow in September.

How to sow radishes, step by step

1. Sow direct — never in modules The part you eat is mostly swollen hypocotyl sitting on one straight taproot, and that taproot has to run down without interruption. Lift a radish seedling and replant it and you get a fork, a kink, or nothing worth eating. Sow where the crop will grow, using the method in our direct sowing guide.
2. Rake a fine tilth — and skip the manure Radish wants a light, crumbly, stone-free seedbed with no fresh manure and no high-nitrogen feed; rich ground gives magnificent leaves and a miserable root. Follow our soil preparation guide, and if your ground is heavy or stony, a topping of sieved leaf mould is the cheapest way to get the fine texture roots need.
3. Sow shallowly and space the seed Cover with 1–1.5 cm of soil, rows 15 cm apart, seed dropped about 2.5 cm apart along the drill. Sown deeper than 2 cm the root sits sunken and misshapen. Water the bottom of the drill before sowing rather than sprinkling afterwards — it puts moisture where the taproot is heading and stops the seed washing into clumps.
4. Thin within a week — the step everyone skips As soon as the first true leaf appears, thin salad radish to 2.5–5 cm apart and winter radish to 10–15 cm. Crowded radishes shade each other, compete for light and answer by making leaf instead of root. A fortnight late is already too late.
5. Sow a short row every ten to fourteen days A metre of row at a time is far more useful than a whole packet at once, because radishes stay in good condition for only a few days. This is textbook succession sowing. Nothing coming up at all? Work through our germination troubleshooting guide.

Salad radish or winter radish?

Two quite different vegetables share the name and the botanical name. Choosing the wrong one for the season is the second most common reason a radish crop disappoints, so decide before you open the packet.

Caring for radishes: water, light and flea beetle

Steady moisture is almost the whole job. A radish that dries out and is then watered heavily splits, because the core resumes growing faster than the skin can stretch; a radish kept dry throughout turns pithy and viciously hot, since the pungent mustard oils concentrate under stress. Aim for evenly damp soil rather than a weekly soaking — the principles in our watering guide apply, but err towards little and often. A thin mulch between the rows holds that moisture in place.

Light is the other half. Radishes sown in the shadow of taller crops make leaf and no root at all, which is why a bed emptied of beans in late summer suits them so well. Flea beetle is the main pest: the adults pepper young brassica leaves with tiny round holes and are worst in warm, dry weather from May to early August. Cover the row with fine insect mesh from the day you sow, or simply sow after the middle of August when numbers are falling. Slugs take the seedlings in wet autumns, and cabbage root fly can tunnel the roots — our guide to common garden pests covers all three, and radish earns its keep as a sacrificial decoy for flea beetle near more precious brassicas, one of the tactics in our guide to companion planting. Remember that radish is a brassica: it shares clubroot with cabbage and kale, so give it its own slot in the rotation rather than following cabbage or mustard greens. Our guide to crop rotation shows where it fits. Pots and raised beds work beautifully because you control the compost and the watering: see growing from seed in containers and raised bed gardening.

Harvesting radishes — and the pods nobody expects

Pull salad radishes the moment they reach size, usually 2–3 cm across. There is no grace period: two or three days past their best and the flesh turns spongy and the heat climbs. Test-pull one at the end of the row rather than guessing, and if a batch is racing ahead of your appetite, pull them anyway and keep them in the fridge with the leaves twisted off. Winter radish is lifted from October before hard frost, its leaves twisted off, and stored in damp sand at 1–4 °C, exactly as described in our guide to harvesting and storing produce.

And if a row bolts before you get to it, do not pull it up. The seed pods that follow the little white and lilac flowers are edible, crunchy and gently peppery — the rat-tail radishes grown deliberately in parts of Asia — and they are excellent raw or pickled while still green and snapping. Left longer, those pods ripen into next year's seed, though radish crosses freely with its neighbours and with wild radish in the hedgerow, so isolate a single variety if you want seed that comes true; our guide to seed saving explains how, and how long seeds last covers testing an older packet before you commit a row to it.

Common radish mistakes

• Sowing in midsummer and blaming the variety — long days and heat tell the plant to flower. The same packet sown in September behaves like a different vegetable.
• Not thinning — the single biggest cause of all-leaf-no-root. Thin at the first true leaf, without exception.
• Feeding the bed first — nitrogen builds foliage. Radish wants soil that was manured for a previous crop, not this one.
• Letting the bed dry out, then drenching it — that swing is what splits roots and hollows them out.
• Sowing too deep — 1–1.5 cm is plenty; deeper and the root sits buried and misshapen.
• Sowing the whole packet at once — radishes hold for days, not weeks. A short row every fortnight is the answer.
• Following cabbage or kale in the same bed — radish is a brassica and shares their soil-borne diseases.

Frequently asked questions

Why are my radishes all leaves and no root?
Three causes, in order of likelihood: the seedlings were never thinned, the bed was too rich in nitrogen, or the row was too shaded. Heat and long days make it worse by pushing the plant towards flowering. Thin hard, choose an open spot, and sow into ground that was fed for a previous crop.

Why are my radishes hollow or spongy inside?
That is a growth check followed by a growth spurt — usually a dry spell ended by heavy watering or rain — or simply a root left in the ground too long. Keep the soil evenly damp and pull promptly; hollow radishes are still edible, just unpleasant raw.

Can I grow radishes in a pot?
Yes, and they are one of the best container crops. Salad radish needs only 15 cm of depth, so a window box or trough works; winter radish and mooli need at least 30 cm. Use fresh peat-free compost, thin as ruthlessly as you would in the ground, and never let the pot dry out.

How late can I sow radishes?
Outdoors, until about the third week of September in most of northern Europe — the crop simply slows as light levels fall, taking six weeks rather than four. Under a cloche, cold frame or in an unheated greenhouse you can keep sowing into October and pull small, sweet roots through late autumn.

No other vegetable gives back so much for so little attention, and none is a better teacher: pull a radish and the soil tells you what it thought of your watering, your spacing and your timing. Sow a row this week alongside lettuce, spinach, corn salad, rocket, turnip, carrot, chard and kale — and read winter lettuce and how to grow spinach from seed for the crops that will still be feeding you in February. Browse our organic seeds or compare types in heirloom vs F1 vs organic, see everything ready to go in at sow in September, and dig into all our vegetable seeds, our full seed range or the rest of our growing guides.