Family: Brassicaceae
Genus and Species: Raphanus sativus
Climate
Radishes grow best in the cool months of early spring and early summer or in the autumn and winter. If radishes are grown in too much heat with sporadic watering, they will become spicy and tough. Given the right climactic conditions: cool temperatures and moist soil, radishes will be a tender crop.
Soil
Grow radishes in cool moist soil. Above all, radishes like consistency - don't let the soil dry out during the growing season. Loose, fertile soil that retains water but isn't soggy is perfect. Mix in organic matter like leaves or compost for an extra boost. Loosen the soil to a depth of 10" before sowing radish seeds. Radishes will grow best in soil temperatures between 60° and 65°. Soil pH should be 6.5 or higher. Soil pH over 6.8 will help manage club root.
Spacing
Radishes grow quickly, most radish varieties mature in 25-35 days. This makes radishes perfect for marking the rows of slower germinating crops like carrots or parsnips. Sow radish seeds in loosened soil about 1/2" deep. Keep them 1-2" apart for small varieties and up to 6" apart for larger varieties. Grow several rows of radishes in a bed but keep your beds at least 2' apart.
Direct Seeding
Direct seed radishes in prepared beds 1/2" deep in loosened, moist soil in early spring and fall in cool climates. In warm climates, sow radishes in late fall to grow through the winter.
Seeding For Transplants
Transplanting radishes is not normally practiced.
Germination
These seeds germinate best in soils around 45°F-90°F.
Germination will take 4-12 days.
Watering
Radishes need consistent moisture. If the soil dries out during their growth, radishes will become bitter and mealy. Keep radishes evenly moist throughout the growing season. Use a straw mulch to help retain soil moisture.
Harvesting
Radishes are mature for a short time, if left in the ground too long radishes will become pithy and mealy. Most radishes take 25-35 days to mature, so watch them during this time and pick a radish every so often to determine their maturity.
Harvest radishes by gently grasping the top and pulling the radish plant from the ground. Use a hand shovel to loosen soil of necessary.
Post-Harvest Handling
Wash and dry radishes thoroughly. Radishes benefit from pre-cooling such as hydro cooling. Hydro cooling is the process of spraying or immersing vegetables in chilled water. Dry radishes thoroughly before storage. Washing radishes in chlorinated water will reduce instances of black spot.
Storage
Store radishes at 32° and 95% - 100% relative humidity. Radishes will last 1-2 weeks in ideal conditions.
Diseases
Radishes are relatively disease free.
Pests
Aphids, Flea Beetles, and Cabbage Maggots.
Comments
Radishes can be grown interspersed with other crops.
References
Bradley, F. M. and Ellis, B. W.(Ed.). (1992), Rodale's All-New Encyclopedia of Organic Gardening: The Indispensable Resource for Every Gardener, Emmaus, Pennsylvania: Rodale Press.
Oregon State University, Radish , Commercial Vegetable Production Guides, Last modified 2003-01-03, http://oregonstate.edu/Dept/NWREC/radish.html, Accessed 2003-7-13
Smith, E.C. (2000), The vegetable gardener's bible: discover Ed's high yield W-O-R-D system for all North American gardening regions., Storey Books: Pownal, VT.