Radish

Raphanus sativus

Last revised February 15, 2010

Radishes take many forms and are used in a large variety of ways world-wide. The common red and icicle types are commonly used fresh as salad vegetables and garnish in the U.S. Oriental types, such as the elongated and round daikon radishes, are less well-known in the U.S. but are important staple foods in countries like Korea, Japan, Taiwan, and others in Asia, and by these ethnic groups in the U.S. These types are used fresh, pickled (as is Kimchi), dried for future use, and cooked in countless Oriental dishes. Seeds of radish are sprouted and these sprouts are another important food in these Asian countries.
Many varieties of radish exist. Some are unique novelties, others are popular for home garden use, and still others are important in commerce. Most are adapted to production in the Pacific Northwest. Only a few are listed below.

Photo credit: Bill Mansour, Oregon State University

VARIETIES

See the Vegetable Variety Selection Resources page to find varieties that have been shown to perform well in the Pacific NW. 


SOIL

Radishes do best on either light mineral soils or muck soils but may be grown on a wide range on soils. Daikon radish requires deep, friable soil for best quality roots.


SEED AND SEED TREATMENT

Radish seed numbers approximately 2,000-4,000 per ounce depending on type and variety. Use hot-water treated seed and fungicide treat seed to protect against several serious seed borne diseases. Hot water seed treatments are very specific (122 F exactly, for 25 to 30 minutes; the wet seed then quickly cooled and dried). The seed treatments are best done by the seed company, and can usually be provided upon request.


SEEDING

Important: Before planting this Crucifer crop, consider the following important factors:

1. No crucifer crop, or related weed has been present in the field for at least 2 years, 4 years preferable. Crucifer crops include cabbage, cauliflower, broccoli, kale, kohlrabi, Brussels sprouts, Chinese cabbage, all mustards, turnips, rutabagas, radishes etc. Cruciferous weeds include wild radish, wild mustards etc. Also, crucifer plant waste should not have been dumped on these fields.

2. Soil pH should be 6.5 or higher. Soil pH over 6.8 is necessary to manage club root. The application of 1500 lb/acre of hydrated lime, 6 weeks prior to planting is recommended for soils with pH less than 7.5 for club root control when planting club root susceptible radishes.

Use a drill with a 2 or 4-inch scatter shoe to drop 24 seeds 1/2 inch deep per foot of row. Space rows 8 inches apart. Oregon growers commonly apply a mixture of sawdust and chicken manure to a depth of 1/4 to 1/2 inch over the planted beds.

Daikon in-row spacing should be 4-6 inches, with rows 24-36 inches apart. Adjust planting rates accordingly. Some Chinese radishes can weigh 100 lbs. These would be spaced 24-36 inches apart in rows 36-48 inches apart.


FERTILIZER

A soil test is the most accurate guide to fertilizer requirements. The following recommendations are general guidelines.

Maintain a pH 6.5-7.0, adding lime or dolomitic lime (if magnesium is needed) as indicated by soil test.

For red globe radish, poultry manure is often used to supply 50-75 lb N/acre. Care is needed to guard against excessive top growth. Excessive N is particularly bad during periods of warm, wet weather. Buildup of soil N during the season results in progressively larger tops, so N applications should be reduced as the season progresses.

Add P and K as indicated below.

Nitrogen rates for Daikon radish should be 130-150 lb/acre. Divide this among several applications, applying two thirds of the total during the last half of the growth period. Adjust N rates and irrigation as necessary to maintain vigorous, uniform growth.

In the absence of a soil test, for both red globe and daikon radish, P, K, S and B, should be applied as follows:

Phosphate: 130-150 (P2O5) lb/acre 
Potash: 100-150 (K2O) lb/acre 
Sulfur: 30-50 lb/acre per season
Boron: 1-5 lb/acre, or as needed according to soil test.

If fertilizer is to be banded at time of seeding, rates greater than 60 lb/acre of potash should be broadcast and incorporated before seeding.


IRRIGATION

Globe radishes are shallow rooted and quick growing, requiring frequent, uniform irrigation for optimum growth and tenderness. Earliest plantings may receive sufficient rain to mature the crop, later plantings may need a total of 5-6 inches of water depending on planting date, seasonal variation, and variety. Use care to prevent excessive top growth.

Daikon radishes require full season to reach maturity, and 12-15 inches of water under western Oregon conditions. For best root quality, irrigate to maintain uniform, vigorous growth.

Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.


HARVESTING, HANDLING, AND STORAGE

The University of California-Davis has a file on Minimal Processing of Fresh Vegetables that discusses film wrapping and other topics.

Red radish may yield up to 800 cartons/acre per crop. Three or four crops may be obtained per season on the same ground. Daikon radish yields would be approximately 15-20 tons/acre.

All harvesting is done by hand. Red radishes are pulled and tied in bunches. The bunches are washed and should be cooled immediately after harvest for best shelf life. Bunches are packed either 2 or 4 dozen/carton. About 90 percent are currently packed in 4-dozen cartons. The 2-dozen cartons are mostly used for shipments to California. Average yield of the 4-dozen cartons is 500-800/acre.

Radishes should be kept moist and cool at all times to prevent dehydration. Daikon radish may be mechanically undercut before harvest.

STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)

Hold radishes at 32 F and 95 to 100% relative humidity. Most spring radishes are topped and packaged in plastic bags. They should be cooled quickly to 40 F or below to maintain their crispness. Hydrocooling is an effective method of cooling radishes. Black spot is reduced by washing radishes in chlorinated water. Topped radishes can usually be held for 3 to 4 weeks at 32 F and a somewhat shorter time at 40 F. They will keep at least a week at 45 F. When temperatures are higher than 32, low oxygen (1%) is beneficial in reducing tip and root growth and softening. The regrowth of tops can be greatly retarded by trimming off the growing points, which are aggregated within a few millimeters on to of the root.

Bunched radishes have a much shorter market life because of the perishability of the tops. They can be held at 32 F and a relative humidity of 95% for 1 to 2 weeks. Addition of package and top ice aids in keeping the tops fresh.

Daikon, Chinese, or black, radishes require the same storage conditions as topped carrots and should keep in good condition for 2 to 4 months at 32 F.


PACKAGING

Topped radishes are commonly packed in 15-lb cartons containing 30 film bags each 6 ounces (Florida); 11.5-lb cartons of 30 film bags each 6 ounces (California) or 25-lb loose packed film bags.

Bunched radishes are packed in cartons of 24-48 count bunches of 6-9 radishes per bunch.

Daikon may be marketed in cartons or 20-lb plastic bags.

Tags:

Fresh Market Vegetable Production, Radishes