Daniel Gill, Merrill, Thomas A.
By Dan Gill
LSU AgCenter Horticulturist
When I was a child my family lived in Germany for a time. I remember attending the annual Oktoberfest in Munich, where thinly-sliced white radishes were served with salt as a nibbler to accompany the famed draft beer.
Although I couldn’t appreciate the beer at that age, I loved the radishes. I also think of radishes in October for another reason, because this is a great time to plant them in your garden, and there are no vegetables easier to grow.
The radish belongs to the mustard, or Brassicaceae, family, which encompasses vegetables as diverse as broccoli and watercress. The small radishes we enjoy so much are known as Raphanus sativus, while the much larger oriental radishes are Raphanus sativus longipinnatus.
Radishes can be classified according to the length of the growing time from sowing to harvest. Short-season cultivars are easy to grow and quick to mature. They are a joy for gardeners anxious to have fresh vegetables for a fall salad, since they are ready to harvest in only 21 to 30 days from the time seed is sown.
These short-season radishes require cool soil to germinate and mild air temperatures to develop well. They can be planted from now through early April (although you might have to protect young plants from freeze damage if temperatures drop into the teens this winter). Cultivars include Cherry Belle, Champion, Sparkler, Snow Belle, Easter Egg, French Breakfast and White Icicle.
Mid-season cultivars were bred in Japan and are excellent for planting in spring (February/March) for an early summer (May) harvest. These large, carrot-shaped radishes grow more slowly, maturing in 45 to 60 days, and have been bred to resist bolting during warmer weather. Cultivars include April Cross and Summer Cross.
Long-season radishes are much larger and slower to mature (50 to 70 days) than short-season varieties. Long-season varieties need warm soil during germination and early growth, but they need short days and cool weather toward the end of their growing cycle. That makes them ideal to plant now for harvest this winter. Varieties include Misato Rose, Round Black Spanish, White Chinese, Sakurajima and German Beer.
A sunny location and a well-prepared bed with good drainage are the simple but important requirements for growing radishes.
Radishes planted in heavy or clay soil will grow slowly and are likely to have misshapen roots. Most radishes, especially long-rooted varieties, will benefit from being grown in raised beds where deep, loose soil can be easily provided. To enrich the soil, add well-rotted compost or manure and work a general-purpose fertilizer into the soil before planting the seeds.
Don’t look for radish transplants at your local nursery. Radishes, like all root crops, are best grown from seeds planted directly into the garden where they will grow.
Sow seeds at least one-half inch apart at a depth of one-quarter inch. Try not to sow the seeds too thickly. Cover the seeds lightly with fine soil. Firm the soil in place gently. Then water with a gentle spray.
Radishes sprout in a matter of days, but they need a constant supply of water to do so. Check the soil daily during this period to see if it is adequately moist.
Unless your family can consume a lot of radishes at one time, plan on sowing small amounts of seed every week or 10 days rather that raising one large crop. Radishes left in the ground past maturity become woody. Successive sowings guarantee a steady supply of young, fresh-tasting roots.
Successful Growing, Harvesting
Plump, juicy radishes are those that grow quickly and continuously. A steady supply of water – at least an inch a week – will ensure rapid, steady growth.
While winter around here usually is fairly moist, October can be dry. Water your radishes when necessary. An organic mulch laid down when plants are 2 inches to 3 inches high also will retain moisture and help keep the soil cool.
Thin radishes when the seedlings are an inch high, so the plants will not crowd each other. (The small plants you thin out can be washed and added to salads.) Plants grown crowded will have abundant leaves but small roots.
Short-season radishes need to be about 2 inches apart, while mid-season radishes require a minimum of 3 inches. The late-crop varieties need even more room, so allow 4 inches to 8 inches between those plants.
For best quality, start harvesting short-season varieties in three or four weeks when they are about an inch in size. Trim the leaves (which can be added to salads) close to the top of the root. Then place them in a plastic bag and store in the coolest part of the refrigerator where they will stay fresh tasting for two to three weeks.
Mid-season radishes will mature in five weeks to six weeks, but they may be harvested as soon as they reach a desired size. Long-season types take more than two months to mature and can be dug immediately or left in the ground for a few weeks.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter.