Originating in China thousands of years ago, radishes spread west via Egypt during the time of the pharaohs, then to Greece, and Rome, and other European countries. They found their way to North America in the late 1500s.
Radishes are quick-growing and generally require 4 to 10 weeks from seeding to harvest, depending on type. They are most often eaten raw in salads, but are also stir-fried, pickled, or used in soups. Most of the flavor is in the skin and diminishes after peeling.
Types & Varieties
Multiple types of radishes exist, with some of the more popular being red or red and white. Varieties include Cherry Belle, Early Scarlet Globe, Red Globe, Champion, Red Prince, Sparkler, Daikon, Black, White Icicle, and California Mammoth White.
Black radishes have a black or dark brown skin with white flesh when peeled, and generally have a longer shelf life.
Radishes germinate at soil temperatures between 65 and 85°F with good moisture, though new cultivars tolerate hot, longer days.
Color will deteriorate when grown on the same land for many years; regular crop rotation can also help avoid soilborne pests and diseases.
Rapid growth ensures a mild flavor and crisp texture while slow growth may result in a woody texture and high pungency.
Pests & Diseases
Cabbage maggots can be a serious threat, as they burrow into plant roots. Flea beetles chew small holes in leaves, often rendering them unsaleable.
Bacterial black spot will develop in storage at warmer temperatures, while black root or black root rot causes misshapen and blackened roots due to bacteria in the soil, and is a serious threat.
Root scurf/wire stem occurs when seedlings are attacked by fungus but survive. If the fungus attacks mature radishes, it is called scurf; symptoms are similar to black root.
Downy mildew occurs at cool, damp weather, causing yellow spots on leaves and a white cottony growth.
Storage & Packaging
Optimum storage temperature is 32°F and rapid cooling is essential to shelf life. Radishes are often top-iced with 95 to 100% relative humidity.
Common radishes maintain quality for 7 to 14 days with tops, and 21 to 28 days without. Daikon radishes may last up to 4 months.
References: Clemson University, Michigan State University, North Carolina State University, University of California, University of Michigan, USDA.
GRADES & GOOD ARRIVAL
Grade standards include U.S. No. 1 and Commercial, providing for two styles of radishes, topped and bunched. Topped means radish tops are clipped back to not more than 0.375 inches in length. “Bunched radishes” have full-length tops, tied in bunches.
Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the USDA or CFIA inspection was timely; and (3) the entire lot was inspected.
|U.S. Grade Standards||Days Since Shipment||% of Defects Allowed||Optimum Transit Temp. (°F)|
There are no good arrival guidelines for this commodity specific to Canada; U.S. guidelines apply to shipments unless otherwise agreed by contract.
References: DRC, PACA, USDA.
• When inspecting topped radishes, the sample size is 50-count; if the bag contains less than 50, additional bags must be opened to attain a proper sample
• The tolerance for decay affecting roots is 1%, for the tops of bunched radishes it’s 5%
• Air cracks are scored as a defect if deeper than .25 inches, or the length exceeds 0.625 inches on a 1-inch diameter root
• Any new top growth found on topped radishes exceeding 0.375 inches in length is scored as a defect.
Source: Tom Yawman, International Produce Training, www.ipt.us.com.