Watermelon radish, also known as roseheart radish and beauty heart radish, is an heirloom variety of daikon radish.
Not only does watermelon radish look amazing, it too tastes fantastic. It makes a superb addition to a wealth of dishes.
In this grow guide, we’ll show you just how easy it can be to grow them at home and impress the guests at your next dinner party.
What is a watermelon radish?
Originally cultivated in China, where it goes by the common name of shinrimei, watermelon radish is closely related to the common radish. It is also a cousin of other plants in the Brassicaceae family, such as Napa cabbage, bok choy, or turnip.
At first glance, watermelon radish looks like an inside-out variety of the common radish. Beneath the light green or creamy white skin, the flesh is an intense pink or fuchsia color, with a striking resemblance to a miniature, seedless watermelon. The taste is also sweeter than regular radishes, with a subdued spiciness and a crisp yet juicy texture.
Watermelon radish produces small, round bulbs, up to 4 inches (10 cm) in diameter. When shopping for organic watermelon radish seeds, you will find them under several common names, usually either Chinese Red Meat Radish or Roseheart Radish. It’s worth noting that the names refer to the same variety.
How to grow watermelon radish
Even if you’re not a big fan of radishes, the watermelon radish’s mild aroma and stunning color will soon change your mind.
Ready to plant it in your garden this year? Then read on to find out how to get started.
When to plant watermelon radish seeds
Watermelon radish is a root vegetable that is best grown as a cold season crop. Depending on where you live, you can even grow this radish in winter if the weather is mild enough.
Finding the right time to sow the seeds can be tricky, but it is essential for four reasons:
- Watermelon radish grows best in temperatures around 60 °F to 65 °F (15 °C to 18 °C);
- They can take up to 65 days to reach maturity;
- Cold temperatures significantly improve the flavor of watermelon radish, lending a pleasant sweetness;
- When exposed to hot soil temperatures, the root can become dry and bitter.
It means that if you sow watermelon radishes too late in spring and are hit by the hot summer temperatures, they will become small and bitter or not grow at all.
As a rule of thumb, avoid sowing radishes if temperatures exceed 95 °F (35 °C), as germination will be almost impossible. What we recommend is that you sow them either in early spring, once any chance of frost has passed, or in late summer or early autumn.
Luckily, finding the right time to sow watermelon radish is the only major hurdle you’ll come across. Once you’ve picked the right season, everything else is plain sailing.
Growing watermelon radish outdoors
All radishes are easy to grow — even the watermelon variety! The seeds are small and easy to sow and don’t require any soaking in advance. They can germinate in temperatures as low as 40 °F (4 °C), so you can plant them directly in your garden soil.
Alternatively, you can start them indoors in compostable seedling pots and transplant them to your garden once each plant has at least 2 sets of leaves.
– Location and soil
Watermelon radish needs around 6 hours of sunlight to grow, so plant it in a part of your garden that gets enough light. Prepare the soil by digging it up, turning it to a depth of 1 foot (30 cm), and incorporating plenty of compost or manure to provide the young plants with nutrients.
This vegetable isn’t too pretentious for soil types and can tolerate almost all pH levels found in the average garden. Just make sure that the soil is well-draining and aerated so that the roots develop correctly.
– Spacing and watering
Sow your watermelon radish seeds 1 inch (2.5 cm) apart, and cover with a thin layer of soil. Water well, keeping the soil moist but not soggy. The seeds will germinate in about 4 to 7 days. When they are about 2 inches (5 cm) tall, you can thin them out to at least 6 inches (15 cm) apart so that the roots have plenty of space to grow. Use the same spacing for transplanting the seedlings that germinated indoors.
When thinning out radishes, the best way to do this is by snipping the leaves with a pair of scissors. Pulling them out of the ground can disturb the other radishes growing nearby, often damaging their roots in the process. Cut the leaves of any radish seedling you want to remove at soil level. This way, the remaining plants will not be disturbed, and they will also have better access to nutrients, light, and room for root bulbs.
If you’ve prepared a nutrient-rich substrate for your plants, your watermelon radishes shouldn’t need any additional fertilizers. However, suppose the soil in your garden is poor in organic matter.
In that case, we recommend using a liquid fertilizer once every 1 or 2 weeks after the seeds have germinated. A nutrient ratio of 10-10-10 should do the trick.
– Maintenance and troubleshooting
As your watermelon radishes grow, you will see that the root bulb’s top is starting to emerge above the ground. When exposed to light, the root begins producing chlorophyll that gives radishes a light green color on the shoulders. If you want to keep the color even, cover the top of the root with a thin layer of soil.
Watermelon radish doesn’t have too many pests and diseases, but you should still keep an eye on your plants as they grow. The leaves make a tasty snack for slugs, snails, and caterpillars. If you want to grow organic watermelon radishes, our recommendation is to avoid using chemicals in your garden. Pick these little pests by hand, and throw them in a bucket of soapy water.
Like all plants in the cabbage and radish family, watermelon radish can be susceptible to clubroot. The clubroot is a fungal disease that can cause the roots to become deformed, essentially killing the plant. Once your radishes get infected with clubroot, there’s no way to save them.
To prevent clubroot, we recommend keeping the soil pH above 6.8 and regularly disinfecting your gardening tools to prevent further spread. Crop rotation once every 2 years is also ideal.
When to harvest watermelon radish
Watermelon radish is a fast-growing vegetable. In the right conditions, it can be ready to harvest in as little as 45 days. On average, they take about 60 to 65 days to reach full maturity. Avoid leaving them in the soil for too long, however, as they will only become more bitter and pungent.
To check if your watermelon radish is ready to be picked, brush off some of the soil covering the root’s top. This should give you an idea of whether it has reached the right size. The best time to pick these radishes is when they’re around 4 inches (10 cm) in diameter. You can also harvest them when they’re about the size of a golf ball, but to get that vivid, pink color, leave them in the soil until they get a bit bigger.
How to harvest watermelon radish
Harvest your watermelon radish by grabbing the bottom of the leaf stalks and pulling the entire plant from the ground. The radish should feel firm to the touch, without any blemishes on the skin. Brush off any dirt on the skin. Cut the leaves and bottom roots, and keep them in the fridge for up to a week. Or better yet, slice it and enjoy it freshly picked from your garden!
Uses for watermelon radish
Watermelon radish is a great vegetable that’s both gorgeous to look at and tasty. The flavor is mild and slightly sweet, without the peppery spice of regular radishes. Younger roots may have a bit of a mustard bite but without any intense aroma. You don’t have to peel the thin skin. That’s where most of the nutrients are stored, especially vitamins A and C and minerals such as calcium, potassium, magnesium, and phosphorus.
The best way to enjoy watermelon radish is to eat it raw, cut into thin slices — you can even sprinkle some black sesame seeds on top to max out that watermelon look. Use it in salads and slaws, turn it into pickles, or you can add it to stir-fries. When cooked, watermelon radish releases its pink color into the food, so you can use it to add a touch of color to your meals. Don’t forget about the leaves! They are also edible and can be used as salad greens or cooked the same way as spinach.
Not only do they look great, but watermelon radish tastes delicious too!
And best of all, they’re easy to grow at home if you follow this guide. Let’s go over the essentials;
- The ideal watermelon radish season is during cooler temperatures, and they grow best between 60 °F to 65 °F (15 °C to 18 °C);
- You don’t typically need to germinate watermelon seeds indoors before planting —be sure to avoid freezing conditions;
- Besides temperature, they’re not very fussy about soil, watering, or fertilizer — like other radish species, and they can even be grown in your old boots!
It is as easy as that — so why not pick up some seeds and try growing these stunning radishes yourself?