Edibles

Radish: Sow and Grow Guide

Radish: Sow and Grow Guide

These cool season crispers are more than bright red slices on a salad. Try roasting or pickling them for a new flavor, or use a more unique variety, such as daikon or Rat Tail. And because most radishes mature quickly, it's a perfect choice for kids learning to garden. However, stress from heat, improper spacing, or drought can cause them to bolt (flower), so follow the guidelines below to grow your best radishes.

GENERAL INFORMATION
Radishes are generally divided into two groups, Spring/Summer, and Winter. Spring/Summer radishes grow best in the cool weather of spring through early summer, and fall. It is usually small, can be globe shaped or elongated, and pungency ranges from mild to fiery spicy. Winter radishes are sown in mid to late summer because they require shortening day length to trigger root growth, need a much longer time to mature, and can overwinter in the ground in mild climates. Winter radishes may be long or round and are usually milder than spring/summer radishes, although some can be pungent. They store well in the refrigerator for up to a month, with tops removed.

GENERAL SOWING
When to Sow Outside:

Spring/Summer Radish
RECOMMENDED. 4 to 6 weeks before average last frost, and when soil temperature is above 40°F, ideally 65°‒85°F. Successive Sowings: Every 1 to 2 weeks until late spring. Sow again in late summer until 2 weeks before average first fall frost. In mild climates successive sowings can continue until temperatures are below 40°F.

Winter Radish
RECOMMENDED. 8 to 10 weeks before average first fall frost. Optimal soil temperature is 65°‒85°F. Successive Sowings: Every 10 days for about 3 weeks. In mild climates, successive sowings can continue until temperatures are below 40°F (60°F for Round Spanish) for germination.

When to Start Inside: Not recommended. Root vegetables are sensitive to transplanting.

OUTDOOR SOWING
Sowing preparation and spacing
Soil should be loose and light with a fair amount of organic matter, free of rocks and clods for up to a foot. Space a group of two seeds 1"-5" apart depending on the variety (see packet).

Growing Temperature
Radishes thrive in the cool temperatures of spring and late summer/fall.

Water
Keep evenly moist. Too little water produces a small, spicy, bitter root. Too much water promotes excess foliage and small root. Uneven watering may cause radishes to crack or split.

Fertilization
Is not necessary with fertile soil. Excess nitrogen can result in large greens and skimpy roots.

Weeding
Keep radishes weeded to prevent stress from crowding, light, or drought, which may cause them to bolt (flower).

Thinning
Proper thinning is crucial for good radish development; thin soon after seedlings emerge.

Special care
Radish plants thrive in cool temperatures, but the seeds require fairly warm temperatures to germinate. If you wish to help warm the soil, you can place black plastic sheeting on the growing area 3 days before sowing. Sow the radish seeds under the sheeting, and after 4 days, check daily for seedlings. Remove plastic immediately after seedlings have emerged.

To produce the straightest, whitest daikon, sow in trenches. As the radish grows, mound soil on top of its shoulder, keeping the shoulder covered to prevent greening.

HARVESTING
Harvest before radishes reach the optimal size listed on the packet and before a hard frost.
If allowed to grow larger than their optimal size, radishes can get spicy and pithy (spongy or hollowed core).

STORAGE
Store washed radish roots separate from their edible tops in a plastic bag or other container in the crisper of the refrigerator.

COMMON PESTS AND DISEASES
Flea beetles can devour the green tops, which impacts formation of the radish root. If you live in an area where flea beetles are problematic, cover seeded area with row covers until harvest.

Radish Comparison

Variety Sub-
category
Type Heirloom/
Hybrid
Root Size Heat
Tolerant
Days to
Maturity
Noteworthy Other
Common Names
Radish Cherry Belle HEIRLOOM Seeds ’Cherry
Belle’
Spring/
Summer
Heirloom ¾"–1½" round 24 Container friendly
Radish Crimson Giant HEIRLOOM Seeds ’Crimson Giant’ Spring/
Summer
½"–2" globe shape 28 Container friendly
Radish Easter Egg Blend Seeds ’Easter Egg Blend’ Spring/
Summer
1"–1½" globe shape 30 Container friendly
Radish French Breakfast Organic HEIRLOOM Seeds ’French Breakfast’ Spring/
Summer
Heirloom 3"–4" long,
1" wide
Heat tolerant 28 Container friendly
Radish Rat Tail HEIRLOOM Seeds ’Rat Tail’ Heirloom 3"–12" slender seed pods Heat tolerant 40–50 Grown for seed pods, not root

Online exclusive
Radish Round Black Spanish HEIRLOOM Seeds ’Round Black Spanish’ Winter Heirloom 3"–4" round 60 Excellent storage variety, somewhat spicy ’Noir Gros Rond d'Hiver’
Radish Watermelon Mantanghong Seeds Watermelon ‘Mantanghong’ Winter Hybrid 3" round 50–60 Excellent storage variety
Radish Daikon Miyashige White Organic HEIRLOOM Seeds ’Miyashige’ White Daikon Winter Heirloom 6"–20" long, 2"–4" wide 60 Traditionally eaten raw, pickled, or cooked


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