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How to Grow: Radishes
If you’re an impatient gardener, like me in the spring, you must grow radishes (Raphanus sativus). This root crop goes from seed to
harvest in as little as 25 days. I’m always amazed at how fast they germinate and grow during our cool spring weather. They add crunch, color, and zip to any salad. As long as they’re grown while the weather is cool, the flavor is pleasant and mild. However, with any kind of stress such as lack of water or hot temperatures, the flavors turns sharp and hot. I personally love a spicy radish, but others in my family don’t.
These spring radishes grow in round or elongated shapes usually white, red, or purple skinned. There are also winter radishes or daikons. These take longer to grow and are best eaten as a fall crop when the cool weather sweetens the roots. Some of these varieties have elongated white roots, round black skinned roots, or green skin with red fleshed roots. I like growing winter radishes for use shredded raw in salads or used in Japanese cooking.
When to Plant
Plant spring radishes as soon as the soil can be worked, usually April or May. Plant again in late August or September for a fall crop. Since they mature so quickly, sow small batches every week in spring to extend the harvest into summer.
Where to Plant
Radishes are very forgiving plants. I once found a daikon growing underneath other vegetables, completely forgotten about, until the fall when I discovered this large root. Since these are root crops, they grow best on raised beds. They only need 3- to 4-hours of direct sunlight to grow and mature. Tuck them in amongst slower maturing crops, such as broccoli, tomatoes, and squash. By the time you pull the radishes, these other crops will have started to expand and fill in the open space.
How to Plant
Amend the raised bed with compost only if you have poor soil. Too much compost or nitrogen fertilizer inhibits the roots from forming properly. Sprinkle the small seeds 1 inch apart in rows spaced 1 foot apart or broadcast the seed over the top of the bed. Don’t worry if you can’t get the spacing down. You’ll be thinning anyway. Cover the seeds with potting soil or sand and water well. They will germinate, literally, within a few days.
Care and Maintenance
When radish seedlings are 1-inch tall, thin them so they’re spaced 2-inches apart. Thin winter radishes to 4-inches apart. Use the thinnings in salads. Some growers just grow radishes for the baby greens to add to mesclun and salad mixes. Keep the bed well watered and weeded. Any stress from lack of water, poor thinning, or weed competition will cause the roots to not form, to crack, or be hot flavored. No extra fertilizer is necessary.
Watch for aphids and flea beetles on young radish leaves. These create shotgun-like holes in the leaves. Spray insecticidal soap to control them or cove the radishes with a floating row cover.
Keep a close eye on your spring radishes. They mature quickly. Gently remove the soil from the base and as soon as you see a round (or elongated) root, pull it up. It you wait too long the roots can become woody textured and hot flavored. Harvest winter radishes the same way, but they will take up to 1 month longer to mature.
‘Easter Egg’ is a mix of white, red, and purple skin colored spring radishes. ‘D’Avignon’ is an elongated red and white skinned variety. ‘Red Meat’ is a round winter radish with red flesh. ‘Miyashige’ is an elongated white-rooted daikon for fall growing.
Text excepted from the Northeast Vegetable and Fruit Gardening book.