Radish

Raphanus sativus

Days to maturity calculated from date of direct seeding.

Radishes are best sown in spring or late summer, maturing when days are shorter, sunlight weaker, and temperatures milder; though some varieties are better able to handle summer conditions.

Culture
• Prepare the bed by working compost into the top 2-3 inches of soil
• Needs consistent soil moisture due to shallow root systems
• Dry or crowded conditions will slow growth and make roots hot or pithy
• The season may be extended from February through October by sowing in cold frames or using row covers
• For extended harvests plant every two weeks

Direct Sowing
• Direct sow spring through early summer
• Three grams will sow 7-8 row feet
• It is essential to thin promptly when they form 2 true leaves
• Sow mid-August—mid-September for a fall crop

Insects & Diseases
• Common insects: See Brassica Insect Information below
• Disease prevention: 5-7 year crop rotation

Harvest & Storage
• Harvest while still young (before splitting); if left in the ground too long, roots develop a strong taste and get fibrous. Winter-grown radishes can be kept in the ground a few weeks after maturity if the weather is cool, but should be harvested before frost
• Harvest the largest roots first to allow smaller radishes to continue growing
• Signs radishes are ready for harvest include greens that are 6-8 inches tall, roots reaching their final size (dependent on variety), and the shoulder, or top part, of the radish pushing up
• Let a few plants bolt and make a seed pod — green pods have a crunchy, mild radish flavor
• Remove tops and the root tail before storing. Wash and dry thoroughly, then place in a resealable bag
• Store at 36°F and 100% relative humidity
• Radish greens can be stored in a produce bag for up to 3 days in the fridge; include a dry paper towel

Brassica Insect Information
Aphids: Control aphids with ladybugs or a hard spray of water or Pyrethrin. Also, select varieties that mature later in the season when aphid populations decline.
Cabbage worms, loopers, and root maggots: The first sign of cabbage worms will be off-white butterflies fluttering near the plants. They lay their yellowish-colored eggs on the undersides of leaves, which hatch into caterpillars that can cause severe root and head damage. To control light infestations, spray plants with Bacillus thuringiensis (B.t.): For heavy infestations, bait cabbage worms by mixing wheat bran into a B.t. solution. Add 1 tablespoon of molasses. Broadcast the bran mixture around the base of plants. Reapply as necessary. Using Reemay or Summer Insect Barrier can also provide control.
Flea beetles: Flea beetles chew tiny pinholes in leaves. Early control is essential to minimize the damage. Spray infected plants with Pyrethrin. Using floating row covers such as Summer Insect Barrier can also provide control.
Symphylans: In some areas of the US, symphylans (also known as garden centipede) can severely impede the plant growth of many crops. Only 1/4 inch long, white, and very active, they eat the root hairs of developing plants. Using larger transplants helps reduce damage. Contact your local county extension agent if you suspect you have a problem.