How to Grow Radishes in Greenhouse: A Step-by-Step Guide for Seed to Harvest

Radish is a small root crop in the Brassicaceae family and is related to cabbage, Brussels sprouts, and broccoli. Additionally, it has been cultivated for centuries and is one of the oldest vegetables. Globally, they’re popular and come in various colors, shapes, and sizes. Radishes can be grown in a greenhouse throughout the winter months with little effort. Sunlight and maintaining a 10°C growing temperature throughout the day are essential.

How to Grow Radishes in Greenhouse

Radish Varieties Suitable for Growing in Greenhouse

Spring Varieties

They grow best in spring and autumn and are the most common in the United States. Due to their small size and short storage life, they’re best eaten fresh. White beauty, cherry belle, and French breakfast are among the spring varieties. From seed to full maturity, the cherry belle variety takes between 20–25 days, while the others take 25–30 days.

Winter Varieties

Winter varieties of radishes, such as daikon and black Spanish, are excellent storage crops. They grow much larger than spring varieties and last much longer if stored properly. The plants are usually planted in late summer to be harvested in autumn, but they take a bit longer to reach maturity. Daikon takes about 50 days or more to mature fully, while Black Spanish takes 30 to 40 days.

Choosing between the two depends on whether you want to grow radishes for storing and using later or if you like to eat fresh radishes. If you want a spring variety, cherry belle and black Spanish for a winter variety are recommended.

Soil Requirements for Growing Radish in Greenhouse

Radishes aren’t picky about soil but prefer rich, well-draining soil with plenty of organic matter. A good quality potting mix soil can be purchased or made yourself. Ideally, your potting mix should be loamy and free of stones if you make it yourself. Make your potting mix rich in organic matter, such as compost or well-rotted manure. Radishes need a lot of organic matter to thrive.

Temperature Requirements for Growing Radish in Greenhouse

Radishes are a cool-season crop, so 10 to 21°C is the ideal temperature for growing them in greenhouses. The plants can still be grown from 4°C to 32°C without any problems. Be careful with the temperature during seed germination, however. During seed germination, the ideal temperature should be between 13°C and 30°C. Seeds will germinate more slowly if the temperature is below or above that.

How to Plant Radishes in Greenhouse

As soon as the soil is prepared, sow seeds directly in the soil beds, 1/2 inch deep. It is best to plant weekly to spread the harvest over weeks instead of days. The rows should be spaced eight to 18 inches apart, and the seeds should be planted eight to ten per foot. Each plant should be thinned to one every two inches.

Once planted, garden areas should be kept cool and well-mulched with compost or aged animal manure. The high temperatures and drought make this root crop tough, strong tasting, and susceptible to insects. It is important not to let the soil dry out.

In case you missed it: How to Grow Coloured Capsicum/Bell Peppers in Greenhouse: A Seed to Harvest Guide

Watering Requirements for Growing Radish in Greenhouse

Water your radishes evenly, and never allow the soil to dry out completely, especially in the first few weeks. Ensure you check your radishes every 2 to 3 days and add water if necessary. The presence of moist soil does not mean you need to overwater them. Rotten roots can be caused by soggy soil. In addition, you should avoid watering radishes irregularly; allowing the soil to dry out and then pouring on lots of water to create really moist conditions can cause the roots to crack.

Fertilizing Requirements for Growing Radish in Greenhouse

Adding compost or aged manure to the soil mix before planting the radishes is necessary if you want them to grow quickly and properly. You can add more fertilizer after two weeks to promote growth. However, too much nitrogen can cause foliage growth and lush tops on radish plants, so it’s best to use a fertilizer with low nitrogen content. To achieve the best results, fertilizer should be applied every 10-14 days.

Thinning Radish Seedlings

Thinning is likely the single most important step when growing radishes. Once radishes reach two inches in height, usually around a week after planting, they should be thinned to three-inch spacings. Too many radishes result in them not growing well, and their roots will be small, shriveled, and unusable.

Thin the greens by snipping them at the soil line. These plants’ nuts are edible, so add them to salads. Alternatively, you can replant the thinnings removed with care without damaging their roots, leaves, or stems. Despite some stress, transplants should be able to recover. Pull any weeds that appear in the row during thinning.

Pests and Diseases in Radish Growing in Greenhouse

In the greenhouse, radishes are resistant to pests and diseases. You may have problems with aphids and flea beetles. To get rid of aphids on your radishes, spray them with water or use insecticidal soap if there are too many. Radishes are susceptible to root rot, which can happen if the soil is too wet and you overwater them. Downy mildew is another common disease of radishes. By keeping your foliage dry and providing proper air circulation, you can avoid this problem.

Harvesting Radishes

Some varieties of radishes are ready for harvest in only 23–30 days, including cherry belle and French breakfast. Daikon radishes, for example, take between 50 and 60 days to mature and be harvested. To determine radishes’ size, uncover the tops of each plant when the time is right, and you’re not sure if they’re ready for harvest. When the tops of the radishes are slightly thicker than your thumb, they can be harvested.

The leaves break off easily when pulled from the soil, so be careful when pulling them. Remove them directly from the root by gently pulling them out. Remove the leaves immediately after pulling them out. Without it, the roots will lose water and shrivel. You can pick the young and green leaves and eat them; they’re tasty and edible; you can use them for salads, soups, and other dishes. Radishes should be washed and stored in the refrigerator.

In case you missed it: A Step-By-Step Guide for Growing Radish Microgreens: DIY in Simple Way from Seeds in Containers

Conclusion

You can grow radishes from seed in just four weeks, making them quick, easy, and fun. Even a small garden can accommodate these compact plants, making great greenhouse plants. Plant small batches every few weeks for harvesting throughout summer for a crunchy tang in your salads. It is even possible to grow varieties for winter crops.

How to Grow Radishes in Greenhouse: A Step-by-Step Guide for Seed to Harvest