Domesticated in Asia even before Roman times, these small round, and generally red root vegetables have made their way into many a salad thanks to a combination of tangy flavor and crunchy texture. But radishes are so much more. They can be oblong as well as round, and they grow in a variety of colors including white, purple, pink, bicolor, or the red of the collective imaginary.
Members of the Brassicaceae family and botanically known as the Raphanus sativus, these root vegetables are annuals that are related to collars, broccoli, kale, cauliflower, and even cabbage. As rapid growers, radishes are generally planted in the early spring for a spring harvest, or at the end of summer for a fall harvest. Smaller cultivars may require barely a month for maturation while larger varieties may need two. In any case, they are much quicker to harvest than other plants.
They can be cultivated in USDA hardiness zones 2 through 11.
Choosing a Location
Radishes like sun, so choose a spot that is sunny for your crop. They can also be planted as companion crops and nestled in next to carrots, or plants that sprout later on because these root vegetables will be harvested by the time other vegetables require more space for growth. Avoid sowing your radish seeds where there is shade caused by trees or other larger plants. Radishes can be cultivated in containers if you prefer.
Till your soil bed ahead of time to remove rocks or clumps of dirt before planting.
When to Sow
Radishes can be planted in the early spring as soon as the earth is tillable. As rapid growers, these vegetables lend themselves successfully to succession planting, so you can sow seeds weekly for a continuing supply. Stop your sowing when your temperatures reach 65° Fahrenheit. Heat will cause radishes to bolt.
They can be replanted at summer’s end or early autumn approximately six weeks before the first projected frost for your area.
How to Sow
Seeds should be planted at approximately a depth of a half-inch and about two inches apart. If cultivating several rows, space your rows at least three inches from one another. When your seedlings appear, thin them to three inches apart.
Growing Radishes in Containers
If you don’t have a garden, but still want to grow radishes, fear not! You can do so in pots. Root systems are shallow so your container won’t need to be particularly deep. You may have better luck with the round varieties as opposed to the oblong varieties due to space.
Choose a container that’s about a foot wide and deep with a good number of drainage holes. Terra cotta pots are ideal because they help with wicking away any excess moisture. Use a high-quality potting soil mix. You will need to monitor water needs closely because container soil will dry more quickly than garden bed soil.
Caring for Radishes
Rich, loamy soil is the ideal growing medium for radishes. It must be well-draining to avoid rot and the soil pH can be neutral to slightly acidic measuring between 6 and 7. Avoid cultivating radishes in heavy soil, or soil that tends to become compacted as root systems will suffer. Soil rich in organic material is best. Amend your soil beforehand if necessary.
Full sun is necessary for a successful crop. Your radishes should have access to at least six full hours of sunlight daily. With partial shade, your radishes will produce more foliage than root.
Water and Humidity
Humidity will not present a problem for radishes if the soil retains enough moisture so plan on giving your plants an inch of water weekly. If the soil bed becomes too dry, plants will bolt to seed early and negatively influence the taste of your vegetables. Too much water places your radishes at risk of splitting open and rotting. If your weather tends to warm and dry out the soil bed, consider mulching around plants to aid moisture retention.
The ideal climate for radishes is when temperatures measure between 40° and 70° F. Anything hotter can cause plants to bolt and ruin the taste. If the plant bolts, the root bulb will cease to develop. They can become spongy and woody. Centers may hollow out. Plants do require good air circulation.
If soil is fertile and rich you will not need to fertilize. If you have poor soil quality, amend it with several inches of compost before sowing seeds.
Pruning is not required for radishes. You will only need to thin out your seedlings once they sprout. Radishes should not be crowded, or development will suffer. To thin, trim seedlings at the ground level. Seedlings are edible.
Do weed regularly to prevent competition for soil nutrients.
Radishes are generally cultivated from seed. If you have mature plants, you will be able to collect your seeds for future crops. However, as radishes will benefit from bees and other pollinators they may cross-pollinate with other related vegetables.
To gather your seeds, leave several radishes in the ground rather than harvesting them. After a while, a flower stalk will appear, and a seed pod will develop. Once seed pods mature, dry out and turn brown, remove them from the stalk. Crush open the pods to remove seeds. Place seeds in a paper bag or envelope and store them in a dry but cool place. Seeds generally have a shelf life of approximately five years.
Pests, Diseases, and Problems
Like many root vegetables, radishes have pests that invade. Common pests to be o the lookout for include:
- Cabbage Root Maggots
Plants will wilt or appear stunted. Foliage will not have a healthy color. To contrast, use collars on seedling stems, and sticky traps. You can start with row covers to prevent infestation.
- Cabbage Worms
Large, ragged holes will appear on the foliage. Eggs will be deposited on leaf undersides and dark green excrement will be present. Row covers are best for prevention. Also, consider growing thyme as a companion plant.
- Flea Beetles
Foliage will feature numerous small holes. Row covers are the best option. Also, mulch will aid in prevention.
Diseases to be aware of include:
This is a fungal infection that will cause plants to wilt and foliage to turn yellow. Roots will look swollen. Destroy any infected plants. Disinfect all tools and maintain soil pH at 7.2 to contrast. Solarize soil bed.
- White Rust
White blister-like lesions will appear on leaf undersides or small greenish-yellow blisters on tops. Destroy any infected plants. Look for resistant varieties when planting.
Depending on the variety you select, some radishes will be ready in as little as twenty days while others may require two months. When the root measures approximately one inch in diameter, you can begin harvesting. You may see the radish begin to sit just above the soil line. In most cases, you will need to pull a radish to evaluate how far along your crop is. Do not wait too long to harvest or the taste and texture will suffer.
When harvesting, pull plants upward out of the soil. Remove the roots and tops by cutting them off. If you leave foliage attached, it will draw energy away from the bulbs. Foliage or greens can be removed and stored in the refrigerator for several days. They can be consumed fresh or cooked. Bulbs should be stored in the crisper drawer of your refrigerator and should last a couple of weeks. Root bulbs can be eaten fresh or cooked. They are favorites in salads and soups.