Radish

Light and exposure

In spring and autumn the radish likes full sun, which makes it grow fast and gives it crunch. Keep a well-exposed spot for the sowings from the end of winter to mid-spring, and again from late summer to mid-autumn.

In high summer it is the opposite. Long days and heat make it bolt and turn it hot and hollow: it is day length above about fourteen hours combined with mean temperatures over 25 degrees that triggers flowering. A spot in partial shade, or the light shade of a taller vegetable, suits it better through the hottest weeks of the year.

Watering

Water is the key to a good radish. Regular watering, without swings, gives tender, juicy, mild roots. The soil must never dry out completely during the crop’s short life.

A lack of water or a crop that drags on makes the radish hollow, fibrous and strong in heat. In dry weather, water every day at the end of the day. A sowing well watered and without interruption is ready in a month, that is the whole secret.

Soil and repotting

The radish thrives in a light, loose, cool soil, neither too rich nor too stony. A soil too heavily manured favours the foliage at the expense of the root. A simple pass with the hand fork and a fine raking before sowing are enough.

In heavy or stony ground the roots deform and fork. A little well-rotted compost and some sand to lighten it clearly improve the shape and the regularity of the radishes.

Temperature and humidity

The radish is hardy and stands the cool far better than the heat. It germinates as soon as the soil reaches 5 to 8 degrees and tolerates light frosts, down to about minus two or minus three degrees, which allows very early sowings.

Direct sowing is possible four to six weeks before your last frost, under a cold frame, a tunnel or a simple fleece that warms the soil and protects from cold snaps. A light fleece gains three to five degrees over the open air. In open ground with no cover, wait rather until the soil holds ten degrees. Conversely, the radish bolts when the days pass about fourteen hours of light and mean temperatures rise above 25 degrees, so you then have to sow it in partial shade or take a break until the cool returns.

Pruning and upkeep

The radish is not pruned, but it calls for careful thinning, the most important operation in its cultivation. Sown too thickly, it makes plenty of leaves and no root. As soon as the seedlings have two true leaves, thin them to leave two to three centimetres between each plant.

To avoid having to thin too much, sow thinly from the start, one seed every two centimetres. The young plants pulled out when thinning can in fact be eaten in salad, leaves included, nothing is wasted.

Pests and diseases

The cabbage root fly can lay at the collar of the radishes, and its larvae tunnel galleries into the roots that make them inedible. An insect-proof fleece laid from sowing is the surest defence, and it also keeps the fly away from the other brassicas.

Flea beetles are the other plague, especially in dry, hot weather. These tiny jumping beetles riddle the leaves with small round holes and weaken the young plants. Soil kept moist bothers them a great deal, and a fleece stops them. Slugs, for their part, attack the seedlings in wet weather.

Propagation

The radish is always sown in place, straight in open ground, because it does not like being transplanted. Sow in rows fifteen centimetres apart, or broadcast on a small bed, only one centimetre deep. Cover with fine soil and water.

To harvest continuously, sow a small row every two or three weeks right through the cool season rather than one large sowing all at once. Emergence is very fast, often three to five days, and the harvest follows three to five weeks after sowing depending on the season.

Month-by-month care calendar

Green Hub tips

• Sow little but often, a small row every two or three weeks, rather than one large sowing at once that all comes together.
• Water makes the radish. Regular watering without swings gives tender, mild roots, a lack of water makes them hollow and hot.
• Lay an insect-proof fleece from sowing. It is the simplest defence against the cabbage root fly and against the flea beetles that riddle the leaves.
• In high summer, sow in partial shade or take a break. In sun and heat, the radish bolts before it even forms its root.