Radish
Raphanus sativus
From its origins, possibly in Southeast Asia, radishes now grow worldwide in many forms.
Introduction
From its origins, possibly in Southeast Asia, radishes now grow worldwide in many forms. They have been bred into long white daikon in Japan, red globe radish in Europe and radish for salad leaves in the UK. There are also winter radish grown as a fodder crop for farm animals.
Radish are in the Brassicaceae family, worth remembering for the shared pest issues.
Harvest period
- Days from seed to first harvest: 35–40
- Best climate is temperate and moist, not too hot, definitely not arid.
Why grow them
It’s a personal call, as not everybody likes radish. My dictaphone calls them rubbish! Actually I love them in very early spring, when the cool conditions mean they are juicy and not too pungent. Their harvest is the first root vegetable of every year.
You can eat radish leaves, and their speed of growth on first sowings of red globe radish makes them a welcome early green. The reason they are not commonly eaten is the spiky leaf-hairs, which are not comfortable on the tongue.
- There are varieties of ‘leaf radish’, which have been bred to grow smooth leaves with a fine radish flavour, without spiky hairs.
Furthermore, there is an incredible range of radish for sowing in late summer, to harvest through the cooler months. They have amazing colours and a decent flavour, plus you can cook them a little. All radish, even globe types which are normally eaten raw, are tasty when lightly fried or sauteed, even roasted. Treat them like turnips, their close relations.
Pattern of growth
Radish are biennials grown as annuals. They flower in spring, but a rapid rate of growth means that you have time to grow a harvest in early spring before they flower. Therefore the harvest of early spring needs taking quickly, before the radish grow woody as they start to make a flower stem.
Autumn harvests just keep growing, and radish resist a certain amount of frost. In cold climates they can be stored as you would a carrot or beetroot – unwashed and in boxes, cool and moist.
Suitable for containers/shade?
They are ideal for containers, thanks to a high speed of growth and not needing a large root run. In 2013, I set up a comparison of three composts in the same sized boxes and noticed little difference. One was old cow manure, and the radish grew as well in this as those in two different batches of homemade compost. One of the composts was from a heap that I had found here in December 2012.
Radish also grow well in shade; in fact, they like more temperate conditions, so shade is good if your climate is hot and dry. Best containers for radish are wide and flat, to give maximum surface area for many leaves to grow, resulting in worthwhile harvests.
Varieties
There are so many! One troubling thing though, which I have noticed recently, is the lack of maintenance given to traditional varieties such as French Breakfast. Also, in 2020 I grew some F1 hybrid radish that were disappointing, compared to traditional carefully selected radish from Bingenheimer Saatgut in Germany.
French Breakfast is a pretty, long radish with a distinctive white tip; it needs eating young and small, often goes hollow when larger and has a mild taste.
Rudi is a firm and dark red, round radish; it stands well without going soft.
Black Spanish is a large winter radish, with white flesh under a dark skin.
Mooli Minnowase grows a long, white mooli radish – a good variety if well maintained, also called Daikon.
Shawo Fruit is a bright green ‘fruit’ radish, semi-long and cylindrical – sow just after midsummer.
Green Luobo has green streaks inside a white exterior, is firm and crisp and good for pickling – sow as for Shawo.
Candela di Fuoco can be sown early or late, grows long and red, as in the photo below, and stays reasonably firm.
Video
Sow and propagate
Even though it is a root vegetable, radish transplants really well. As with beetroot and turnips, the root part that we eat is actually a stem swelling just above root level.
- Seeds germinate in two to four days, perhaps the fastest vegetable.
Sowing time
For red globe radish, sow under cover in late winter to early spring – early spring is good for direct sowing outside. The summer sowing is in early autumn, either under cover or outside direct.
For larger, winter radish, sow mid to late summer.
Sowing method
Using module trays, sow five seeds per cell, and thin to four seedlings if need be. Four in a clump gives a lovely sized radish, and plenty of them!
For sowing outside, draw a drill about 5 cm/2 in deep from the top to the bottom of the drill, and make the drills as close as you can, as little as 15 cm/6 in apart. Seed at a spacing of approximately 1 cm, or three per inch.
You can also sow radish in the same drills as your carrots and parsnips – see Lesson 8, Course 3A, and Lesson 22.
Transplant, interplant
Transplant size and time
Seedlings grow rapidly under cover, but for first sowings it’s still early in the year and quite cold, so they are often about four weeks old when you transplant them. Later, when it’s less cold, they can be as little as two weeks old, and it works really well to transplant smaller rather than larger seedlings.
Transplant method
Radish seedlings make long stems, therefore your planting holes want to be on the deep side. Push in the module cells firmly so that all stems will have soil or compost around them.
You don’t need to fill the holes after transplanting because watering will do that for you. It’s good to water in straight after planting.
- Early plantings benefit from a fleece or row cover, both for weather protection and against flea beetles, birds and rabbits.
- You can keep a cover on until harvest time, resting on the leaves – they easily push it up.
Spacing
For red globe radish, very little space is needed, just 15 cm/6 in between multisown clumps. Your direct-sown seedlings may need thinning to 1 cm/two or three radish per inch.
Winter radish need 5–10 cm/2–4 in of space, in 20 cm/8 in rows, or 30 cm/12 in between clumps.
Water
Radish are watery, so keep soil moist most of the time. Nonetheless, it is still possible to give too much water, as with any plant. Remember that excess water means a reduction in soil air. In dry weather, a good dose of water twice a week should be sufficient.
Transplant size and time
Seedlings grow rapidly under cover, but for first sowings it’s still early in the year and quite cold, so they are often about four weeks old when you transplant them. Later, when it’s less cold, they can be as little as two weeks old, and it works really well to transplant smaller rather than larger seedlings.
Transplant method
Radish seedlings make long stems, therefore your planting holes want to be on the deep side. Push in the module cells firmly so that all stems will have soil or compost around them.
You don’t need to fill the holes after transplanting because watering will do that for you. It’s good to water in straight after planting.
- Early plantings benefit from a fleece or row cover, both for weather protection and against flea beetles, birds and rabbits.
- You can keep a cover on until harvest time, resting on the leaves – they easily push it up.
Spacing
For red globe radish, very little space is needed, just 15 cm/6 in between multisown clumps. Your direct-sown seedlings may need thinning to 1 cm/two or three radish per inch.
Winter radish need 5–10 cm/2–4 in of space, in 20 cm/8 in rows, or 30 cm/12 in between clumps.
Water
Radish are watery, so keep soil moist most of the time. Nonetheless, it is still possible to give too much water, as with any plant. Remember that excess water means a reduction in soil air. In dry weather, a good dose of water twice a week should be sufficient.
Harvest times and methods
How to judge readiness
You can pull red globe radish as soon as they are visible and identifiable. The first small radish are sweeter and milder than later ones, so it’s good to begin early.
You will probably have a fair amount to eat from one sowing, and starting to harvest early gives more time to eat it all. As it warms up in spring, you suddenly have an abundance, and mature radish develop a pungent flavour, especially in hot weather.
- Once you see any flower stem, best harvest all radish because they are now becoming tough in texture.
- Winter radish stand for a long time without losing quality. Harvest once they look close to the size you want – they can remain in the soil for a long time.
How to pick
With multisown clumps, you can twist out individual radish and leave the rest to grow some more. Or, if you have a lot coming ready, simply twist out whole clumps.
For intersown radish between carrot and parsnip, easing them up carefully does not disturb the surrounding seedlings, as shown in the photos above. The carrots and parsnips look a little straggly for a while, then grow strongly.
When to pick and how often
Red globe radish lose moisture rapidly after harvest, so you may be harvesting every day or two, for the juiciest roots.
Winter radish are more solid in texture and keep well after picking, like turnips, so you can harvest them ahead of eating.
Storing
Root vegetables lose moisture through the leaves immediately after harvest, so twist off leaves as soon as you have picked the radish, give them a rinse in cold water and they are good to eat for two or three days, just kept in a bowl.
For winter radish, keep them cool – they can stand a little freezing. In a box in the shed, they can store for two to three months.
Saving seed
As long as there are no other flowering brassicas nearby, this is not too difficult. Flowering is in early summer. Seed pods are also edible when green, sometimes called ‘rats’ tails’.
Have six or up to ten of the best quality radish, growing quite close to each other; put a stake in the ground nearby and tie their flowering stems to the stick. Once seed pods are mostly dry, pull all plants and hang them upside down in a ventilated place, under cover. Later you can rub out the seeds at your leisure.
Potential problems
Pests
Spring radish leaves are manna from heaven for flea beetles, which feast on small and tender leaves. Hence my recommendation to cover, using fleece on early plantings to also increase warmth. Then use mesh covers on later plantings.
Another common pest is cabbage root fly, especially by late spring – it can ruin whole sowings. The little maggots tunnel into radish roots and quickly cause enough rotting to spoil your chances of a decent meal. Once again, covers are the answer, and sowing early helps so that harvests happen before the flies are too common. More flies hatch in early autumn, when mesh covers may also be needed.
Slugs chomp into radish roots. As usual, I recommend having minimum slug habitat nearby, no old and rotting wood for example. Plus no dig reduces slug population through better soil structure and the presence of more slug predators.
