Radishes Good for Any and All Seasons

Question: Can I grow radishes year-round?

J.D., Orange

Answer: Among our most popular garden vegetables, radishes are easy to grow, relatively pest- and disease-free, and mature quickly. Round, red or white radishes are ready to pick in 21 to 28 days, and 60 to 75 days for the long-season Daikon types.

The short-season radishes, the fastest growing and most popular, come in many varieties, including the best-selling ‘Cherry Belle’ and the Inca variety, which has better heat resistance.

Daikon radishes have flesh ranging from white, pink, purple and black. Their taste also varies, from bland to very hot. ‘White Chinese’ is a mild-flavored radish that is 6 to 8 inches long and pure white. Daikons are day-length sensitive; as the days get longer, they get hotter in flavor.

Members of the brassicaceae family, radishes are among the most ancient plants. They were cultivated by the Egyptians in 2780 BC. There is evidence that workers on the great pyramids ate them. Unlike we see today, those radishes were dark-colored, large-rooted vegetables. In 16th century Europe, radishes often were used for medicinal purposes.

The round, red radish with which we are familiar today first appeared in the 18th century, and now there are more than 250 cultivars of this radish in various shapes, sizes and colors.

In Asia, radishes are an important root vegetable and are eaten raw, sliced and cooked, and preserved. In the U.S. and Europe, radishes are thought of mostly as crunchy, nippy-flavored salad vegetables.

To grow these almost fool-proof vegetables, you need soil that is rich, well-draining, stone-free and slightly acidic (5.8-6.8). Radishes need six hours of sun daily, but can use some shade in hot inland areas.

Radishes can be grown in the ground or containers. Sow short-season radishes 1/2-inch deep and 1 inch apart and daikon types 3/4-inch deep and 3/4-inch apart. For a steady supply, sow radishes every one to two weeks. Plant fast-growers between rows of slower crops such as carrots.

Keep radishes evenly moist. A single day on the dry side can slow growth considerably. The faster radishes grow, the better their flavor.

Harvest round, red radishes when they reach the size of a cherry or somewhat larger. When left in the soil too long, their quality declines. Store with leaves on and do not rinse until ready to use. Most will keep two weeks in the refrigerator in an airtight container.

Harvest winter radishes when they have reached a desirable length (generally 6 to 10 inches long). To store, cut the tops off 2 inches above the root and place in a plastic bag and refrigerate.

Although root maggots aren’t common in the home garden, they can attack radishes. Minimize the risk of getting them by not planting radishes in the same spot where other brassicas have grown such as broccoli and cauliflower.

If you find dark spots on your radishes, your soil is boron-deficient. This can often be corrected by mulching with compost. Radishes are pollinated by insects and all cultivars will cross, so for true reproduction, plant only one cultivar.

If you let the plants go to seed, you can eat the radish flowers. Seeds are viable for five years. Store in an airtight container in a cool, dark location.

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Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send e-mail to ucmastergardeners@yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days. Please include your name and city of residence.