When to plant radishes – to get a tasty crop year round

Ever wondered when to plant radishes and where to grow them? 

These petite rainbow colored root vegetables bring a vibrant taste sensation to myriad dishes. Radishes are a low maintenance crop which can be planted in the ground, in a greenhouse, on a patio or balcony, and are small enough to even be planted in pots indoors on a windowsill, making them perfect for novice gardeners to grow. They are also an extremely quick crop to grow – their root and edible leaves can be ready to eat, from seed to fork, in four weeks.

The most important first step in how to grow radishes is when to plant them. Get this right, and you can be enjoying a homegrown harvest, high in vitamin C and packed with antioxidants, year round. 

When to plant radishes

Whatever space you have available, however small, it is always possible to plant a pot or two of radishes, or direct sow seed on your plot as part of your vegetable garden ideas. But gardeners will often be wondering when to plant radishes, and if it too cold or too hot? 

'Radishes germinate quickly in early spring temperatures between 45-70ºF (7-21ºC). Plant radishes as soon as the soil can be worked, and consider using them to mark the lines of slower germinating summer crops, such as carrots,' explains Marianne Willburn, Virginia based gardening author, columnist and Small Town Gardenerblogger.

'Many varieties can be harvested within three to four weeks,' adds Marianne. 'This makes them a perfect complement to early spring salads, and a terrific first crop for children who need only wait five to six days to spy the broad first leaves emerging from the soil.'  

Try sowing little and often; successional sowings in spring will ensure you have a continuous harvest with no hunger gaps. Try growing elongated ‘French Breakfast,’ round red ‘Champion,’ heirloom varieties ‘Sicily Giant’ or ‘Bunny Tail’ or carrot-shaped ‘White Icicle.’

What month is best to plant radishes?

The best month to plant radishes will depend on whether you are sowing seed direct outdoors, starting off the seeds under glass, and also the climate where you live.

A prime month for sowing radish direct in the ground is from April, once the soil warms up and the cold winter temperatures have given way to the warmth of spring. 

A fall sowing, in September, is also ideal as the heat of summer mellows and radishes are less likely to bolt.

To make the best and most productive use of growing space, particularly if you have a small vegetable garden, 'sow radish outdoors between slower crops, such as parsnip,' advises Mary Payne MBE, horticulturalist, garden designer and president of Fagus Gardening Club.

When can I plant radish outside?

Radishes can be sown in spring and the fall, avoiding frosts and the dizzy heat of summer. Check local weather conditions, but in many USDA zones radish can be sown outside from April once the risk of frost has passed. 

As part of planning a kitchen garden, radishes are often sown between other slower growing crops as a ‘catch crop,’ where you get a quick harvest while you are waiting for other crops to mature. Most radishes prefer full sun so ensure they are not over shadowed by other crops. 

Radishes do not grow well in heat. The baking temperatures of summer can cause plants to wilt, bolt and go to seed, so avoid planting radishes outside in summer. 

For fall sowings, Mary Payne advises using selected winter varieties, 'sometimes known as Daikon or Mooli, such as ‘China Rose.’ They will be much slower growing.'  

These varieties have been bred for winter cultivation. The name actually means ‘big root’ and has an additional benefit of breaking up compacted soil. ‘Mooli’ have long, white roots, which are slower to mature and develop over 60-75 days. Daikon radish has a mild flavor, great for winter salads.

When to plant radishes under cover

If you're wondering when to plant radishes under cover, you'll be pleased to learn that they are an ideal crop to grow indoors all year round. 

As temperatures plummet in colder zones, you can sow radishes from late fall and throughout winter in a heated greenhouse, propagator or on a sunny windowsill. 

You can even sow in the heat of summer under protection, just water them more throughly. 

Start early radish sowings indoors

To maximize the growing season, you can also start early radish sowings indoors and transplant seedlings outside once temperatures in your local zone have risen. Keep them well watered to allow their tap roots to swell.

'You can start sowing under glass, in a tunnel or even on a sunny windowsill from mid-February, once the light levels start to improve. Radishes need to be grown fast. I like ‘Cherry Belle,’ a round-rooted type,' explains Mary Payne.

Alternatively, grow radishes in pots indoors from late winter as part of your vegetable garden container ideas, then move pots outdoors once the risk of frost has passed in your zone. Pots are a handy way to grow your own food on a balcony or patio and allow you the flexibility to change pot location if conditions change.

Seeds need heat to germinate so grow radish in a protected environment and you will be able to enjoy this crunchy addition to dishes even in the heart of winter.