Radishes are usually thought of as a root vegetable of the Brassicaceae (cabbage) family although tops are equally as edible when treated like collard or mustard greens. Radish roots come in a multitude of shapes and colors—round, oval, barrel, tapered, long; red, purple, white, pink, multi, and even black. They are often categorized as spring, summer, or winter types; European or Asian; mild or hot. Mild, red, European, spring radishes are the most popular and found year-round in markets.
- Growing periods depend on the variety and season. Spring radishes, planted in spring or fall, mature quickly, some germinating in 3-7 days, maturing in 3 weeks.
- Fast-growing varieties such as classic ‘Sherry Belle’, ‘Early Scarlet Globe’, and ‘Crimson Giant’ can be interplanted with other crops and harvested before they shade neighboring, slower-growing seedlings.
- Most small-rooted radishes grow best during cool months of spring and fall and bolt when days are longer and heat is higher.
- Large-rooted winter daikon types take 6-10 weeks to mature, planted in late summer or early fall for harvest in late fall and winter when they can be stored in the ground for short periods.
- Spring radishes become woody and bitter if left in the ground past maturity.
- A few varieties, such as ‘White Icicle’ and ‘French Breakfast’, withstand limited summer heat but benefit from some shade when days grow longer.
Multi-Task Daikon Radish
- More than 100 varieties of daikon types, known as white or winter radishes, range from mild to spicy, white to pink to black. They develop bulky roots and a large rosette of edible leaves.
- Daikon radishes are generally slower growing than spring radish cultivars and exhibit more versatility, raw or cooked.
- Most varieties take 8-10 weeks to mature.
- Roots may be round but more often are carrot-shaped or cylindrical from a few inches to nearly 2 ft. long and may weigh more than a pound.
- Some gardeners plant varieties for their large, long roots to break up compacted soil, then turn under thick tops as a green manure. Length may be stunted if soil is too compact.
- Daikon radishes can be grown nearly year-round, but they are primarily considered a winter vegetable. They are damaged by a hard frost, rot in very cold weather, and bolt in high heat.
Sowing and Growing Radishes
- Rotate beds of cabbage family vegetables every 2-3 years to prevent soil-borne root diseases.
- Plant radish seeds in moist soil fortified with compost but without supplement nitrogen that produces tops at the expense of roots.
- Plant fast-growing varieties in shallow beds or containers during spring and fall when temperatures are 50-75 degrees.
- Plant winter daikon varieties in late summer or early autumn in deep, loose soil in beds or containers. Allow enough time for roots to enlarge up to 12 in. before winter cold stymies growth and quality. Frost, however, improves flavor and texture of most winter varieties.
- Direct sow seed ½ in. deep and thin to 1in. apart for small roots, 4-8 in. apart for larger ones. Transplant thinnings or use in salads.
- Consult seed packet directions for optimal time for harvesting each radish variety.
- Sonoma County Master Gardener Vegetable Planting Summary