Radishes - SARE

Raphanus sativus (Brassicaceae or cabbage family)

Production

Soil preparation

Radishes should not follow other cole crops.
Apply compost and other amendments based on the results of a soil test.
Spread lime as needed to increase both the pH and Ca levels. Dolomite lime will also increase Mg levels. Spread gypsum when calcium levels are low but pH is correct.
A fertilizer company can add OMRI-listed potassium sulfate to compost if it doesn’t have enough K to meet the crop’s needs. If this isn’t possible, spread the correct amount of fertilizer and incorporate it before planting. Alternatively, you can side-dress it during cultivation. Divide the recommended rate of the soil test in half if side-dressing.
Test for boron and apply only as recommended by the soil test. A fertilizer company can add boron to compost to optimize boron distribution. If this isn’t an option, distribute soluble boron through a water solution with a sprayer directly on the soil. If applied directly on the crop don't exceed more than 1 lb. of boron per acre to avoid leaf burn.
Jang, Sutton Jr. or Planet Jr. planters in combination with small seeds like radishes don’t perform well with plant matter on the soil surface, so avoid planting them after tall green manures.
Create a fine and firm seedbed when direct seeding radishes. Prepare the seedbed a few weeks before planting to encourage weeds to germinate. This provides the opportunity for some initial weed control via shallow cultivation or flaming.
Alternatively, place a silage tarp over the prepared and irrigated seedbed 3–5 weeks in advance of the seeding date (depending on the time of year). This will flush many annual weed seeds and reduce weed pressure. Remove the tarp when the weeds have died.

Common recommended fertilizer rates¹

Nitrogen	Phosphorus	Potassium	pH
120	0-125	0-200	6.0-6.4
¹Rates are for New York and are from Cornell University’s Nutrient Guidelines for Commercial Vegetable Production (2019). Check the Cornell website for updated guidelines, or consult with local experts for recommended rates outside New York.

Varieties

Washington State variety trial
Crunchy Royale, Sora, French Breakfast, Easter Egg, and the watermelon radish variety Red Meat for storage.

Direct seeding information

Seeder	Rows	Seeds per foot	Seed plate no.	Depth (inches)	Sprocket setting	Notes
Planet Jr.	5	15	8	2-4		Use row covers after planting for flea beetle control
MaterMacc	5	20	16	1/4-1/2		1 mph
Jang	5	12	X12 or X24		24 Holes: front 11/rear 13; 12 holes: front 14/rear 9

Number of successions

Under ideal growing conditions, radishes take a month to mature from seeding to harvest.
Plant radishes as soon as you’ve prepared the ground in the spring. For continuous harvest, plant the next succession when the cotyledons are fully developed. Depending on your location, continue successions until approximately the first frost date. In New York, this means that the first successions have an approximate interval of 14 days that narrows to an interval of 7 days by late May.
Watermelon radishes for storage are planted in mid- to late August in New York. Adjust planting date according to your region.

Cultivation procedures

Use a basket weeder or wheel hoe when weeds are in the white thread stage, without burying the young crop. Weed control is more effective when you eliminate weeds before they emerge.
You seldom need hand weeding when planting radishes at the correct population.

Frost, disease and insect protection

Control black rot (Xanthomonas) by purchasing clean seeds, keeping the greenhouse clean and exposing seed to hot water treatment. Some organic seed suppliers hot treat their seeds, so check with them before applying your own treatment, as double treatment can affect germination.
Check the soil for wireworms, as a high population can cause radishes to become unmarketable. To avoid wireworm damage, rotate with crops like onions, lettuce or alfalfa, or include buckwheat as a cover crop the previous year. Some results have been obtained using beneficial entomopathogenic nematodes. Promising results have also been obtained applying Beauveria bassiana.
Cabbage maggots: To reduce infestations of cabbage maggots on young seedlings, cover seedlings with floating row covers or insect netting, as you would for flea beetles. Maggots appear in 3–4 generations in the Northeast, starting in early spring.
Flea beetles
- Cover the crop with floating row covers or insect netting before emergence to avoid flea beetle damage. Keep covered until harvest. Alternatively, use a spinosyn-based product like Entrust.
- Fall-planted radishes don’t need any protection after the third generation of flea beetles, which is around September 1 in the Northeast. If possible, follow Extension bulletins that publish the timing of each generation of flea beetles, or place yellow sticky cards at plant height to monitor their presence. Check the cards at least twice a week.
- Spray beneficial nematodes on heavily infected land to control flea beetle grubs and avoid future generations. Flea beetles tend to overwinter in nearby hedgerows and grass strips.

Other cultural practices

Irrigate frequently for optimum yield and plant health. Frequency depends on soil type, evaporation, precipitation and the particular needs of the crop.

Double cropping and/or cover cropping

You can plant fall lettuce or spinach after early radish crops.

Harvest

Yield	An average of 0.5 bunches of marketable radishes per row foot. Watermelon radishes yields are measured in pounds (harvested without tops), and yields range from ⅓–½ lbs. per row foot.
Standards	Harvesting¹ 60-80 bunches per person per hour.
Standards	Washing 150 bunches per person, per hour
Tools and supplies needed	Rubber bands or twist ties (customer preference may influence this), and regular 1⅓-bushel boxes
¹Harvest rates don't include the time required to transport crops from the field to a wash and pack shed or storage facility.

Ready-to-harvest and quality indicators

Radishes are about 0.75–1 inch in diameter.
Radishes are round, similar in size, have good color, and are free of blemishes and cracks, and contain no pithiness.

Harvest procedures

Wash hands before harvesting radishes.
One person harvests several rows of radishes, preferably in the morning. Keep harvested radishes in the shade.
Depending on their size, 1 bunch contains approximately 10–12 radishes, which is common in CSA shares and at farmers’ markets. When wholesaling, a bunch needs to contain 10–12 radishes and weigh 0.5–0.75 lbs.
Only take radishes that are free of blemishes and without splits.
Hold the radish bunch with one hand and put the rubber band over the radish end of the bunch two times. Make sure all radishes stay in the bunch, but don’t make it so tight that stems break.
Don’t count and box the bunches as you make them. Instead, place 4–5 bunches in a pile. When there are quite a few piles on the ground, someone can pick them up and pack them into 24- or 48-count harvest boxes.

Washing procedures

Wash hands and rinse boots before entering the wash-and-pack shed, and cover up field clothes with a bib. If a long-sleeve shirt contains soil, remove this as well.
When washing radishes, use a rinse conveyor or a mesh table to properly clean off the soil from the roots. Some growers have connected a valve operated by a foot pedal to a stationary nozzle to free up a hand, which increases efficiency. Treat radishes gently as they can easily break off the stem.
Radish leaves are quite fragile. Protect the leaves with your hand when spraying directly at the bunch.
Dunking radishes to clean off the leaves isn’t recommended, but when necessary, add a sanitizer to the wash water. Use the guide How to Wash Produce Using a Peracetic Acid Solution to establish how much peracetic acid solution to add to water.

Additional resources

Packing and storage summary for radishes

Cleaning in the field	Yellow leaves are discarded or pulled out of the bunch.
Packing in the field	48 bunches to a picking crate
Packing for delivery	48 bunches weighing 20 lbs., or 24 bunches weighing 10 lbs., in a regular 1 ⅑-bushel box. See the International Federation for Produce Standards for the correct PLU code. Add the prefix 9 for organic crops.
Storage	32° and 95% humidity. Radishes are not sensitive to ethylene exposure and produce very low levels of ethylene.

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.