Radishes are the quickest crop in the Florida garden, ready about three to four weeks after sowing, which makes them a good first crop and a good one for children. They belong to the cool season here. The common mistake is leaving them in the ground too long or growing them into warm weather, which makes the roots tough, hot and bitter.1, 2
The Florida Vegetable Gardening Guide lists September to March for North and Central Florida and October to March for South Florida. Sow seed where it will grow; radishes are poor candidates for transplanting because moving them disturbs the root. Sow again every two weeks or so for a steady supply, thin early, and tuck rows between slow crops such as carrots. Daikon (winter or Asian radish) grows well in Florida but is planted wider: EDIS HS1370 gives 4 to 6 inches apart in rows 3 feet apart, 0.5 to 1 inch deep, and about 50 to 60 days to maturity.
near neutral (Gardening Solutions); 6 to 7 for daikon (EDIS HS1370)
Water
Keep soil evenly moist and loose. For daikon, HS1370 warns that drought gives rough, poor-flavored roots and waterlogging causes rot, and that heavy rain or overwatering can crust the soil and hold back seedlings.
A cool-weather crop that tolerates cold and will survive a freeze; daikon is cold-tolerant to about 25 F. Hot weather and over-maturity are what make radishes pungent and bitter. Small round radishes do well in containers. Loosen the soil before sowing root crops.
Whiteflies, aphids, mites and caterpillars: Occasional problems shared with other cabbage-family crops; Gardening Solutions suggests checking plants each time you water. HS1370 adds that whiteflies and aphids can spread viruses to daikon.
Nematodes: Listed by Gardening Solutions among occasional radish problems.
Root rot: Occasional in garden radish; HS1370 describes a bacterial root rot of daikon that can spread through irrigation water.
Mustard sawfly: Feeds on young daikon leaves and shoots (HS1370).
Pull small radishes young, about 20 to 30 days from sowing; do not let them over-ripen. Larger types take longer: Gardening Solutions and HS1370 both give about seven weeks in spring and ten weeks in fall for daikon. The whole plant is edible, and young greens are good raw or cooked.
The FAO manual names radish: it puts radish among the bulbing and root plants but says it needs fewer nutrients than beets, onions or carrots (p. 92), and advises growing root vegetables including radish in wicking beds attached to media beds rather than directly in the water (p. 169). SRAC 454 does not mention radish.
What this lesson doesn't cover yet
No UF/IFAS home-garden fertilizer rate for radish was found; fertilizer left null.
HS1370 gives radish planting dates of October to March for Central Florida, while the Florida Vegetable Gardening Guide gives September to March; the guide's dates are used.
Your county extension office and its Florida Master Gardeners can fill these in for your garden.