How to Grow Radishes: The Complete Guide

Because of their size and speed, radishes may be grown just about anywhere. But ready to enjoy in as little as four weeks and taking up minimal space, perhaps their best use is as a fill-in crop, either between or within rows of slow-to-germinate vegetables such as parsnip, or as a quick, in-and-out crop right at the start or end of the growing season.

Radishes prefer full sun but grow well in partial shade, too, and in hot climates, will prefer full shade in the height of summer. Choose a sunny spot that gets at least six hours of sun a day. If radishes are planted in too much shade, or even where neighboring vegetable plants shade them, they will put all their energy into producing larger leaves. 

Keep the soil moist, and you’ll be rewarded with clusters of mildly peppery roots in next to no time.

Till the soil (roots do not grow well in compacted soil) and remove any rocks. If the soil is clay, mix in some organic matter to loosen and improve drainage. If you’re planting longer varieties (such as ‘White Icicle”), till to a depth of 8 inches.

When to Plant Radishes

• For a spring planting, sow seeds 4 to 6 weeks before the last spring frost.
• For a fall crop, sow seeds 4 to 6 weeks before the first fall frost.

 See local frost dates here.

Sowing Radishes Early in Plug Trays

Begin sowing under cover from late winter, either directly into containers of potting soil, into greenhouse borders, or into plug trays of general-purpose potting mix.

Fill plug trays with potting mix, firm down, then sow a pinch of three to five seeds per module. Cover with a little more of the potting mix, then water. If it’s especially cold, you’ll need to germinate them indoors and then move them back into a greenhouse or cold frame as soon as the seedlings appear. After a couple of weeks of sheltered growth, and once the seedlings have filled out their modules, they’ll be ready to plant out under row covers or hoop houses.

Plant into soil earlier enriched with well-rotted compost or manure and raked to a fine tilth. Remove the clusters of seedlings from their modules, then dibber a hole for each plug. Drop in the plug and firm it into position so each cluster’s about 6in or 15cm apart in both directions. Cover the seedlings with row cover or horticultural fleece, properly held down at the edges, until the weather warms up.

How to Plant Radishes

Of course, sowing radishes directly where they are to grow is the easiest way to start them off. As cool-season crops, some radishes can germinate at temperatures as low as 41 Fahrenheit or five degrees Celsius. Sow from very early spring, initially under row covers or hoop houses, spacing rows about 8in or 20cm apart. Sow thinly along the row—ideally, so seeds end up spaced around half an inch or one centimeter apart. Water if it’s dry, and then, about a week after germination, thin the seedlings to leave them an inch or 2cm apart within the row.

• Add organic matter before sowing, but also avoid fresh manure or fertilizers high in nitrogen; overly rich soil will encourage lush foliage at the expense of radish roots.
• Radish seeds have a fairly long shelf life. Don’t be afraid to plant radish seeds that are up to 5 years old. All may not germinate, but you’ll have plenty that will.
• Direct-sow seeds outdoors about 1/2-inch deep and cover loosely with soil. Space 1 inch apart in rows 12 inches apart. Water seeds thoroughly, down to 6 inches deep.
• Sow another round of seeds every 10 days or so while the weather is still cool for a continuous harvest of radishes in the late spring and early summer.

Grow Some Radishes for Winter

Many hardy radishes can be sown towards the end of summer to give an autumn or early winter harvest of roots. Sowing regular red, round or white-tipped radishes into containers is a great way to extend the season—by simply bringing pots under cover when the weather turns cold.

Another option is to grow bigger winter or Asian varieties of radish, which naturally prefer cooler temperatures. The most popular is the daikon or Japanese mooli radish. Look out for Chinese and Korean varieties, too—all with a mild flavor that is ideal for salads but also great in soups and stews. Then there’s the stunning watermelon radish or the chunky, spicy Spanish Black radish, whose peppery tang holds up well in stir-fries.

Winter radishes are leafier than their summer cousins. The spicy leaves may be used like spinach, wilted into hot dishes, or even whizzed up in a pesto.

Sow winter radishes a little further apart, so rows are at least a foot or 30cm distant, then thin the seedlings to leave at least a couple of inches or 5cm between each plant.

Check out this video to learn how to plant radishes: