Radishes are an easy-to-grow root crop that is suited to both a spring and fall harvest. They are quick to mature, which makes them ideal for succession planting. If you want to grow radishes in your garden, here is everything you need to know.
You can also download my How Do I Grow Radishes? one-sheet and keep the free resource handy for your reference.
Most radish varieties are a shade of red or purple, but there are also white varieties known as daikon radishes. Then there are watermelon radishes, which are white and green outside and pink inside surrounded by a white ring. Growing a mix of radish varieties will help to stagger harvest times so you will have fresh radishes at the ready for weeks on end.
Raw radishes are crisp with a peppery flavor. Sliced thin, they go on salads or can be served with butter and salt. Raw radishes can also be julienned into “matchsticks” then sprinkled on tacos or grated into a sauce. Pickled radishes can be used in a variety of ways. Whole or cubed radishes can be roasted, and pureed radishes can be the basis for soup. Young and tender radish greens can be eaten as well.
Where, When & How to Plant Radishes
As a root crop, radishes do not transplant well and are best direct sown in the garden. Because radishes are so quick to grow, there really is no reason to try to get a head start by starting the seeds indoors.
Radish seeds will germinate in soil that is as cool as 40° but the optimal soil temperature for germination is between 65° and 85°. In that range, germination will occur in three to six days.
A spring crop of radishes can be planted very early: Start sowing seeds three to six weeks before the average last frost date for your area. For a continuous harvest, sow additional rows each week until the air temperature reaches 65°.
Radishes require full sun, which is between 6 and 8 hours of direct sunlight daily. The soil should have a pH of 6.0 to 7.0, which is slightly acidic to neutral. A soil test will tell you the pH level and inform you of any nutrient deficiencies. The soil should be fertile, light and well-drained to allow radishes to grow to their full potential. Heavy clay soil must be amended with a generous amount of compost in order to grow radishes successfully. Work the soil down 6 inches or more to account for the length of the radish taproot.
To sow seeds, use your finger, a stick or a pencil to create a row of holes that are a half inch to 1 inch deep. Place one seed in each hole and backfill. Leave 12 inches between rows. When seedlings emerge, thin them to approximately 5 inches apart.
For a fall harvest, start sowing seeds four to six weeks before the average first frost date. You can continue weekly sowings for about a month.
All cultivated radishes are of the species Raphanus sativus. You have many options of size, shape and color to choose from, and some varieties are faster to mature than others.
Alpine is a white Korean hybrid radish with green shoulders. The radishes grow to be 5 to 8 inches long and more than 2 inches wide with a flavor that is sweeter than Japanese types. Alpine matures in 55 days.
Bacchus is a deep purple hybrid variety. The radishes are small and globe-shaped, maturing in just 24 days.
French Breakfast is an open-pollinated long red variety with a white tip. The radishes as 3 to 4 inches long and close to an inch wide. French Breakfast matures in just 21 days.
Dragon is a red Chinese hybrid variety. The radishes are crisp with a mild flavor and are next harvest once they reach 4 to 5 inches long. Dragon matures in 40 days.
KN-Bravo is a hybrid purple radish that is purple and white inside. The radishes grow 4 to 6 inches tall and up to 3 inches wide. This variety matures in 49 days.
Miyashige is an open-pollinated Japanese daikon radish that looks like a large white carrot. The radishes grow to be 16 to 18 inches long and up to 3 inches wide. This variety is intended for fall harvest. Miyashige matures in 50 days.
Nero Tondo is an open-pollinated Spanish variety that is black on the outside and white on the inside. The plants are resistant to bolting and the radishes are round, 2-to-4-inch globes. It matures in 50 days.
Red Head is a hybrid variety with white globes that are bright red on top. Red Head matures in 35 days at 1 inch.
Red Meat is an open-pollinated variety of watermelon radish that grows to be 2 to 4 inches wide, white at the bottom, green in the middle, and dark toward the top. The insides of the round radishes are shades of pink. Red Meat matures in 50 days.
Sora is a heat-tolerant open-pollinated variety. The radishes are small red globes that mature in 22 days.
Starburst is a hybrid watermelon radish that matures in 60 days. The radishes are light purple inside with pink streaks that give them their name.
Radishes require rather consistent moisture to avoid becoming tough and unpalatable. An inch of water a week is the goal, so if it hasn’t rained that much, make up the difference with supplemental watering. If the soil is very sandy and especially fast to drain, water more than once per week.
A light mulch such as 2 inches of straw or shredded leaves will help to retain moisture while also suppressing weeds.
Radishes shouldn’t require any supplemental fertilizer if they are planted into soil that has been amended with compost. In fact, applying a fertilizer that is high in nitrogen can cause the radish tops to grow vigorously at the expense of the taproot. An organic fertilizer that is balanced or that has more phosphorus than nitrogen can help radishes along, but you should get a soil test before applying any fertilizer that could be unnecessary or detrimental.
Radish Pests & Diseases
To avoid radish pest issues before they start, cover your crop with floating row cover immediately after planting seeds. Row cover allows light and water through while keeping insects out, so the insects can never land on your crop and lay their eggs.
Radishes are the favorite meal of flea beetles. In fact, radishes are sometimes used as a trap crop to keep flea beetles away from other crops. Both larval and adult flea beetles damage plants. Flea beetles may be in the soil already waiting for something to be planted, or they can fly in. You can knock back a flea beetle problem with insecticidal soap, but you need to be vigilant and make repeat applications.
Radish root maggots are the larvae of tiny flies. Affected plants will wilt and have stunted growth. Using floating row cover before the flies have the opportunity to lay their eggs is the best control. If you already have root maggots, pull the crop and dispose of the plants in the trash — not in your compost pile, where the maggots will continue to mature.
Aphids are sap-sucking insects that sometimes prey on radishes. They are of concern because they spread plant diseases. Again, use a floating row cover to keep this pest at bay.
Radishes can be subjected to a number of diseases, including, but not limited to, Alternaria, white rust, root rot and radish mosaic virus. Get your seed from a reliable source to avoid seed-borne pathogens and practice good garden sanitation to avoid spreading diseases. Sanitize your tools before cultivating the soil and discard any diseased plant material. If radish pests or diseases do become a problem, practice crop rotation to reduce recurrences.
Because radishes are quick to grow, check your garden often. Radishes that are left for too long or were planted too late in spring will bolt (go to seed) in the heat. Bolted radishes are woody and should be composted.
Know the size at maturity for each variety and know what variety you planted where. Radishes push up out of the ground when they are close to maturity. When they are the ideal size, grab onto the foliage and pull straight up while twisting.
Cut off the green tops and the thin part of the root at the bottom before storing. Take the unwashed radishes and place them in damp paper towels inside a zip-lock bag and refrigerate for up to a week. Use the radishes as soon as you can for the best flavor. Radishes left for too long will lose their crispness and become soft.
What are your secrets to growing radishes successfully? Let us know in the comments below.
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Links & Resources
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