Radishes will either break your heart or send your gardening self-esteem to the moon. If you follow a few simple guidelines, baskets full of crisp, peppery radishes will find their way to the dinner table or market in a mere 30 days. But if you go astray, you might end up with pencil-thin, wiry radishes or roots that are too woody and spicy to eat. If perfect homegrown radishes have eluded you in the past, try again. These crunchy and delicious vegetables deserve a place in your garden—and on your plate.
1. Plant Early
Radishes are a cool-season crop, and trying to grow them in warm weather is a big no-no.
“The biggest problems we’ve had when growing radishes are weather-related,” says Sara Bozelli, owner of Five Elements Farm in Worthington, Pa. “When spring temperatures rise well outside of the norm and we don’t get rain, the radishes don’t grow well.”
Optimal soil temperature for radish germination is between 50 and 65 degrees F for both winter and spring radishes, and sowing seeds first thing in the spring is a must in most parts of the country; fall and winter radishes, however, perform better than spring-sown ones in the Deep South. Sow your first batch of radish seeds six weeks before spring’s average last-frost date. For Bozelli, that means she’s in the garden planting spring-grown radishes every few weeks, beginning in mid-March and continuing until late April, though she says they get excellent results from fall radish sowings, as well.
A fall crop can be sown eight to 10 weeks before the first expected fall frost. “Fall is another perfect time to plant radishes,” says William Adams, co-author of The Southern Kitchen Garden (Taylor Trade Publishing, 2007). “The pressure from bugs is lessened greatly, and the temperatures are very conducive to producing nice radishes. They come to maturity so quickly!” Adams suggests that southern gardeners also plant radishes in the fall and continue to sow seeds weekly throughout the winter months.
When the appropriate planting time arrives, begin by preparing the soil. “Soil is the most important element in your garden,” Adams says. “Lousy soil, lousy garden—it’s that simple.”
Amend radish growing areas with several inches of organic matter, such as compost or well-aged manure, a few days to a few weeks before planting. “Almost regardless of the ‘soil hand’ you’re dealt, you can amend it to be a productive soil,” Adams adds. “Secure organic matter however you can. A yearly, even seasonal, addition of organic matter is not an option; it’s a necessity.”
Because the edible portion of this vegetable extends below the soil surface, a properly prepared seed bed helps to ensure well-developed, unforked roots. Loosen the soil to a depth of 12 to 18 inches before sowing seeds 1/4 to 1/2 inch deep.
“Root crops, such as carrots, turnips and radishes, are almost always directly seeded into the garden rather than planted from transplants,” Adams says. “That’s because transplanting these plants will usually result in damage to the tap root, causing a misshapen or forked root.”
To plant, broadcast the seeds over the soil surface and lightly rake them in to create a bed of radishes, which will need to be thinned in the seedling stage. Furrow planting is also an option: Use a hoe or other tool to open up a shallow trench, sprinkle the seeds into the furrow, and lightly cover them with soil. To avoid the thinning process, space the seeds 1 to 2 inches apart.
2. Test Your Soil
Radishes require a balance of nutrients as they grow; however, as with all root crops, they rely heavily on phosphorus for proper root formation. Testing your soil’s pH and nutrient content every few years is an absolute necessity. Root crops thrive in a pH range between 6 and 7, and they use good amounts of phosphorus and moderate amounts of nitrogen. Over-application of nitrogen fertilizers encourages top growth and sacrifices large, well-formed roots.
Because phosphorus doesn’t readily travel in the soil, the zone from which your plants can absorb it is relatively small and quite close to the root itself, meaning if your soil test indicates a need for phosphorus, it should be applied as a side-dressing. Favorite sources of organic phosphorus include rock phosphate and bone meal.
At Five Elements Farm, Bozelli fertilizes her radish crop with compost and a dose of organic, liquid fish emulsion about 15 days after sowing the seeds. Fish- and kelp-based liquid fertilizers provide a quick shot of nutrients to plants—something especially important for fast-maturing crops like radishes—along with necessary trace nutrients and plant-growth hormones.
3. Harvest On Time
Consult your seed packet’s “days to maturity” number when harvesting radishes; leaving them in the garden too long means they’ll turn bitter and quickly go to flower or the bulbs might crack open.
“Radishes mature quickly,” says D.J. Herda, author of From Container to Kitchen (New Society Publishing, 2010). “When they’re ready to harvest, you’ll see the shoulders of the bulbs popping out of the soil line. Harvest and use them as soon as they are large enough.”
To harvest radishes, simply pull them from the soil with your hands or pry them out with a small spade. Many of the nutrients contained in radishes are found in the colorful skin. Pass this information along to your customers and recommend they not peel radishes before eating, but rather simply cut off the greens and any small, stringy roots, scrub them well, and enjoy their crisp texture and snappy taste. The greens can also be sautéed or braised.
4. Keep Pests Away
Radishes can be targets for several different pests. Public enemy No. 1 is the flea beetle. While healthy radish plants can put up with a significant amount of damage from this small, black, fast-hopping insect, seedlings can be killed by heavy infestations.
“Flea beetles can do a lot of damage to the leaves, weakening the plants,” Bozelli says. “We prevent them by growing our radishes under floating row covers. This seems to be especially important for us in the spring.”
Flea beetles can also be deterred with regular applications of kaolin clay, a natural product sprayed on the leaves, covering the plant in a powdery, white film. Flea beetles and other insect pests don’t like to land on the powder to feed.
Wireworms and root maggots can also be problematic for radish growers as they tunnel through the roots. Wireworms are the larvae of several species of click beetles, while root maggots are larval flies. Both can be prevented by using floating row covers to prevent access to egg-laying adults.
Fall tillage helps limit numbers of these insect pests. It exposes developing larvae and pupa to both freezing temperatures and predators, such as spiders, ground beetles and numerous species of birds.
Get more growing advice from HobbyFarms.com:
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- How to Grow Beans
- 9 Soil Tips for Growing Better Asparagus
- 4 Compact Squash That Save Garden Space
- 4 Orchard Fruits You Never Thought to Grow
About the Author: Horticulturist Jessica Walliser is the author of the brand-new book Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control (Timber Press, 2014). She grows six radish varieties and especially enjoys them thinly sliced between two pieces of buttered bread. (Radish sandwiches are seriously delicious!) You can connect with Jessica at www.jessicawalliser.com.