Radishes: Answers to Frequently Asked Questions About Growing, Storing, and Cooking

Radishes
Radishes, Image Courtesy of Graur Razvan Ionut, FreeDigitalPhotos.net

Radishes are easy to grow, they mature quickly, and they’re available in a variety of pretty colours and shapes, so they’re a great choice for children’s vegetable gardens or adult novice gardeners. Easter Egg is a particularly fun variety for kids, as it produces radishes in a rainbow of purples, pinks, lavenders, reds, and whites.

This article answers questions about spring radishes (also called summer radishes), the more commonly grown type (spring radishes can also be grown in the fall). However, most of the advice for spring radishes is also applicable to the larger winter radishes, though they take longer to grow.

What are the health benefits of radishes?

Radishes provide vitamins C and B6, folate, potassium, magnesium, and calcium, and they’re very low in calories and high in fiber. As a member of the brassica family (which also includes broccoli, brussels sprouts, and cabbage), they contain compounds such as indole-3 and sulforaphane, which have shown anti-cancer action in animal studies.

When should I plant radishes?

Plant radishes in the spring (2-4 weeks before the last frost) and late summer to early fall (8-10 weeks before the first frost). You can start planting a bit earlier in the spring and continue planting a bit later into the fall if you provide some protection, such as a cloche, cold frame, or hoop tunnel (polytunnel).

You can also plant radishes in the mid-summer, but they prefer cooler temperatures (around 55-65 Fahrenheit), though they will tolerate temperatures that are somewhat lower or higher. In hot weather, radishes can develop a very pungent, spicy flavor, more like horseradish, or bolt (put their energy into flower and seed production rather than root production). You’ll have better luck with summer plantings if you choose heat-resistant varieties such as D’Avignon, White Icicle, or French Breakfast and provide partial or light shade.

For a continuous crop, succession sow radishes every couple of weeks. It’s better to plant them regularly than to grow a big batch all at once because they are at peak flavour for a very short time and should be harvested and used during this optimal window.

Where should I plant radishes?

Plant radishes in full sun in cooler climates. In hotter climates, choose a spot that is lightly shaded during the hottest part of the day.

Radishes should be planted directly in the garden rather than started indoors, as they don’t transplant well.

How deep should I plant radish seeds?

Plant radish seeds approximately 1/2 an inch deep.

How far apart should I plant radish seeds?

Plant them 1-2 inches apart, and thin to 2-4 inches when the plants have 2-3 leaves (you can eat the leaves of the thinnings – they’re good in salads).

Can I grow radishes in the shade?

If temperatures are warm to hot, radishes can tolerate light shade.

What type of soil do radishes need?

Radishes prefer loose, well-drained soil (they do poorly in heavy, clay-type soils). Adding a small amount of compost and working it into the top 6 inches of soil will significantly improve growing conditions. You don’t want to add too much compost, however, or the plants will put their energy into the production of lush leaves at the expense of root development.

Can I grow radishes in a container?

Radishes have shallow roots, so they do well in containers. Use a container at least 4 inches deep (and preferably 6), and water regularly, as container soil tends to dry out more quickly than garden soil, and radishes need consistent moisture to produce good roots.

How long will radish seeds take to sprout?

In the right conditions, radish seeds should sprout in 3-10 days, but they can take longer if the temperature isn’t ideal.

Should I fertilize radishes?

Spring radishes don’t typically require fertilization. In fact, high-nitrogen fertilizers can be counterproductive, because they encourage the plant to put its energy into making lush leaves rather than plump roots.

What ongoing care do radishes need?

Weed and water regularly to keep the soil moist. If the soil dries out, radishes can develop a woody texture and harsh flavour. Watering should also be consistent, or the roots may crack. On the other hand, you don’t want to make the soil waterlogged, because the radishes grown in soggy soil will have very little flavour and will be more likely to crack.

How long do radishes take to grow?

Spring radishes mature quickly, in just 3-6 weeks, depending on the variety.

When should I harvest radishes?

Spring radishes are harvested in the spring, early summer, and fall. You can continue growing and harvesting them through the late summer, but heat can reduce their quality. In milder climates, you can continue growing and harvesting radishes into the early winter.

Radishes are at their prime for a very short window of time, so it’s important to harvest them promptly. They usually taste best when they’re 1 inch or less in diameter, so gather them while they’re still small.

Why didn’t my radishes form any roots?

If your radish plants produced only leaves, they didn’t have the right growing conditions. The most common cause is failure to thin the plants to 2-4 inch spacing. When radishes are crowded together, they compete for resources. Insufficient light or water, nutrient deficiency, or overly hot temperatures can also cause this problem.

Why do my radishes have a strong, unpleasant flavour?

Radishes get overly pungent and spicy when temperatures are too hot, they don’t receive enough water, or they’re left in the ground for too long.

Why do my radishes have a woody or pithy texture?

This is caused by high temperatures or insufficient water, or because the radishes weren’t harvested early enough.

Why are there holes in my radishes?

Cabbage root maggots and cutworms bore holes in radishes. You can protect your plants with floating row covers.

If the holes are in the leaves rather than the radish roots, the culprits are usually be flea beetles, which can also kept out with row covers, though slugs and snails may snack on radish leaves as well (see Natural, Non-Toxic Ways to Control Garden Slugs for tips on dealing with these pests).

Why are my radishes flowering early?

Radishes bolt (flower) early due to stressors such as overcrowding, nutrient-deficient soil, insufficient water, and long summer days.

Can I eat radishes after they’ve flowered?

The radish root probably won’t taste good anymore, but you can eat the unripe seed pods.

If your radishes were accidentally left in the ground for too long, you can still get something out of the crop by waiting for seed pods to develop and harvesting them while they’re still young and tender. I haven’t tried them myself, but other gardeners say they’re delicious in salads and stir fries. Some like them so much that they deliberately let some of their radishes bolt to obtain the pods, or they grow a variety called Rat’s Tail specifically for its pods (not the most appetizing name, but apparently they’re very tasty).

How do I store radishes, and how long will they keep?

You can store radishes for a couple of weeks in the fridge in a plastic bag or container (though they taste best when eaten shortly after harvesting). They’ll last longer if you don’t wash them until you’re ready to use them.

How do I save radish seeds?

Just wait for your radishes to flower and produce seed pods, and then for the seed pods to ripen. When the seed pods have dried and turned brown, remove and crush them to release the seeds. Store the seeds in a cool, dry place.

You can also cut the pods off once they’ve turned brown and finish drying them indoors if they aren’t drying sufficiently outside.

Save seeds from the last radish plants to flower, not the first, as you’ll want to grow plants that are slow to bolt.

Different radish varieties will cross-pollinate, so they should be isolated from one another if you plan to save seeds.

When stored properly, radish seeds keep for approximately 5 years.

How do I use radishes?

Radishes are usually sliced or grated and added raw to salads, slaws, dips, and sandwiches, or made into pickles.

For delicious radish recipes, see Real Simple’s 13 Tasty Radish Recipes and Bon Appétite’s Rejoice! More Radish Recipes Than You Know What to Do With.

For more vegetable and herb gardening articles, see the main Gardening page.

References:

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    • Herriot, C. (2010). The Zero-Mile Diet: A year-Round Guide to Growing Organic Food. Madeira Park, BC: Harbour Publishing.
    • Jabbour, N. (2012). The Year-Round Vegetable Gardener. North Adams, MA: Storey Publishing.
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