Radishes (Raphanus sativus) are peppery-tasting root-vegetables belonging to the Brassica family.
Red radishes, mainly grown here, originated in Eastern Europe.
They have been cultivated a long time and were popular in Egypt at the time of the Pharaohs.
Radishes are quick and easy to grow, perfect for first-time gardeners.
They tolerate a wide variety of conditions and do well in pots.
Grow in a sunny spot with some afternoon shade. Harsh all-day sun can cause radishes to “bolt”. Radishes grown in shade focus their energy on producing larger leaves.
Radishes like rich, friable, slightly acidic soil (pH 6-7), free from rocks or clods. Lime the soil if the pH is below 5.5. Dig in sand to improve drainage in clay soils. Work in compost or aged manure to boost nutrient levels.
What to plant this weekend
- Butternut squash
- Spring onions
- Sweet potatoes
Fresh manure will burn the root tips and cause the roots to fork. If your soil has a boron deficiency your radishes will be misshapen, split and have roots with brown flecks. Add borax.
Radishes can be grown year-round. Certain varieties thrive at different times.
French radishes are the most common, ideally grow in summer, mature quickly, have round or cylindrical roots, and are mainly eaten raw.
European radishes are larger and longer, prefer winter, take longer to develop, and are cooked like turnips in soups and stews.
Oriental varieties, including daikon, thrive in autumn, take twice as long to mature as the European radishes, and are usually cooked or pickled.
Sow seed 6mm deep. Cover lightly with a sprinkling of compost. Drench with seaweed solution to encourage germination and strong seedlings. Plant every 10 days to extend the harvest.
Herbs to plant this weekend
Radishes grow best from seed and should not be disturbed or moved once planted.
Radishes need space. Sow seeds uniformly. Thin after they sprout to 5cm apart for salad radishes and 10cm apart for daikons. Thinnings can be added to salads. Excessive plant densities will produce irregular sized and misshapen roots.
Soil should be moist and well drained. Water regularly to prevent cracking or bolting to seed, but do not let them sit in wet soil. Drip irrigation is beneficial. Frequent watering supports rapid growth.
Do not overfeed with nitrogen or radishes develop huge leaves and impoverished roots. It can also result in forking. Instead drench weekly with compost tea.
Radishes appreciate mulching to smother weeds and keep the soil moist. Growth slows during cool, cloudy weather. Radishes tolerate light frosts which do not affect mature roots, but heavy frosts damage young leaves.
Tip of the week
- Radish seeds have a long shelf life. Five-year-old properly stored seeds have a 50/50 chance of germinating.
Harvest at four to seven weeks, when the roots are 2.5cm diameter at the surface.
Pull a radish to check before harvesting the crop. Lift while young and tender. Left too long, they become woody and tough.
Greens can be harvested at any stage.
A four-year crop rotation is recommended to prevent build-up of diseases such as clubroot, pythium root-rot and white-rust. Radishes can be affected by downy mildew. Soft rot is a problem with daikon in hot weather. Sudden deluges can cause radishes to split and rot.
Major pests include aphids, cabbage-white butterfly, root-knot nematodes, and vegetable weevils. Pick caterpillars by hand. Slugs and snails demolish seedlings and chew grooves in the roots. Remove by hand.
Rat’s Tail and Dragon’s Tail radishes are grown for their seedpods rather than their roots.
The pods have a tangy, spicy flavour.