Radish Growing Masterclass: 4 Weeks to Harvest

Radishes are crazily quick-growing, going from seed to root in as little as four weeks! This is the fastest vegetable you can grow, but like any veggie, we want bigger and better harvests, which I practically guarantee with the tips I’m about to reveal…

Rainbow Radishes

A bit like beetroot, salad radishes come in a range of colours, including the common red but also yellow, white, pinks and purples, and you can often find rainbow seed mixes for sale to give you a range of tones from the one sowing. All the more reason to grow radishes! And radishes are also incredibly good for us, with high levels of sulphoraphane, which can help to calm inflammation.

How to Get an Early Start Sowing Radishes

What’s super-fantastic about the radish’s double-quick growth is that it throws open so many ways to sow and grow it. I could sow radishes direct into the soil, into containers, or into plug to transplant later.

Sowing into plug trays has a few advantages:

• You can start the radish season off sooner, while the soil is still cool, by making the first sowings under cover.
• You can protect emerging seedlings from slugs.
• You can overlap crops by getting your radishes underway while the ground’s still occupied by an earlier plant.

To sow into plug trays, sift some all-purpose potting mix and gently firm it in to the plugs. Sowing just one seed per plug would make for an inefficient use of time, space and potting mix, which is why I always multisow them into plug trays. Sow up to five seeds per plug. All of the seedlings that come up will be planted in a group, without needing to be thinned out.

Cover the seeds with a little more potting mix, and water them. Radish seedlings should be up within just five days or so, and it’s maybe only seven to 10 days after that that they’ll be ready to beplanted, so they won’t stay in plugs for long! It’s best to get them planted sooner rather than later.

How to Direct Sow Radishes

Sowing directly where you want your radishes to grow makes sense when you have space in your garden to get on and do that, and it saves the extra step of planting pre-sown plugs. It’s how I make most of my sowings once things have warmed up in spring.

Excavate drills (shallow trenches) about a half inch (1cm) deep. Space your drills 8in (20cm) apart. Sow one seed every inch (2-3cm). They’re relatively easy-to-handle seeds, so it’s worth picking up and dropping the seeds individually if you can, to get spacing just so. It takes a little time but means no wasted seed and it isn’t half satisfying to do! Then cover the seeds over with soil, and water thoroughly to wake them up.

If you don’t fancy being quite as meticulous in spacing out every seed or have trouble making steady sowings, don’t worry – just sow as thinly as you can then simply remove any overcrowded seedlings once they’re up to leave them around an inch apart. You may find this easier if you’re sowing a bigger area.

Radishes are also perfect for container growing – just space the seeds an inch or two apart then cover. Remove some of the seedlings if necessary so they’re nicely spaced, then harvest roots as they reach the size you want.

Radish is a cool season crop that germinates at temperatures as low as 41ºF (5ºC), making it a great choice as one of the first direct sowings of the season. On the flip side hot weather can prove a real challenge to radishes, causing plants to bolt (flower and go to seed), which will leave you with little in the way of tasty roots. So, if you’re sowing in the warmer months, opt for a shadier spot and keep the plants well-watered.

And if you’re in a really hot climate, you may find it less trouble to just concentrate on spring and autumn sowings, avoiding the heat of summer altogether, which radishes really won’t enjoy…which makes me think radishes are my kindred spirit!

How to Plant Radishes

Radishes do best in soil that’s had about an inch (3cm) of organic matter such as compost added to it over the winter (or any time up until planting), which should offer more than enough nutrition for these quick growers. Space clusters of multi-sown seedlings a bit further apart than if you were growing single radishes sown directly in rows – about 6in (15cm) apart, in a block formation. Lightly firm each cluster in as you go.

If planting early in the season, cover the planted seedlings over with a row cover of garden fleece. Not only will this help keep them cosier and speed growth, it also hides the seedlings from birds like pigeons which are very, very hungry at that time of year!

Intercropping With Radishes

If you don’t have much growing space, you can turn the small and quick-growing nature of radishes to your advantage. Plant some plugs of radish around other plants, for instance slower-growing brassicas such as cauliflowers while the bigger crop is still quite young. They won’t need the full space in the bed for a few more weeks, allowing you to sneak in a cheeky bonus crop of radishes.

Parsnips are another good option for intercropping with radishes. Sow radish seeds at the same time you sow your parsnips, directly into the same row. Parsnips can take up to four weeks to germinate but the radishes pop up far quicker. That means you can easily see where you’ve sown your rows so you can safely weed in between them. But, more importantly, this gives you an extra crop. The radishes will be good to harvest long before the parsnip seedlings need the space, so you’ll get two root crops from the same area.

So think opportunistically – where can I sneak in a few rows, or even a few clusters of radishes? Can they fill an odd bit of space that’s not going to be used in the next month or so, or squeeze them in between slower-growing or taller crops?

Growing Radishes

Easy-growing radishes are ideal for anyone starting out on their gardening journey – fast and generally trouble-free. The main way to keep them happy is to water whenever it’s dry. This not only ensures steady, uninterrupted growth, it also stops the roots from developing a woody texture, becoming too spicy or potentially splitting. And, of course, pull or hoe out any weeds that pop up.

Flea beetles are perhaps the most common pest you’re likely to come across. The tiny, shiny beetles get their name because they jump away like fleas when disturbed. The beetles feed on the foliage, causing a smattering of tiny holes that scar around the edges. A little damage is okay, but a severe infestation may slow plants down and affect root growth.

Flea beetles are most active from mid to late summer. You can avoid their unwanted raspings by growing radishes outside of this time, or by covering your crop with insect mesh or horticultural fleece to keep them off. I find the damage is typically just cosmetic, and it’s the root that really matters, so a little foliage damage can be tolerated.

Some gardeners actually use the attractiveness of radishes to flea beetles to their advantage by planting rows of radish around the perimeter of other brassica crops like cabbage to intercept the beetles before they reach the main crop.

Another companion planting technique is to plant radishes to deter cucumber beetles. Studies have shown that radishes actively repel these troublesome bugs, which makes the unassuming radish a powerful ally for growing alongside susceptible crops like cucumbers, melons and squash.

Harvesting Radishes

Watching radish roots start to fatten up is always exciting – I swear you can almost see them grow once that magical tipping point arrives! Check plants every couple of days and as soon as they reach a useable size, pull them up and enjoy them.

If you’ve multisown your radishes to grow on in clumps, carefully twist free the biggest roots to leave the rest of the clump undisturbed to continue growing.

Don’t let roots grow too big or they may become hollowed out or spongy. In my opinion, the younger roots have the best flavour – not too hot and with an irresistibly crisp crunch.

Because radishes mature so quickly you can have a steady supply from spring right through until hard frosts stop play. Just remember to make regular sowings – say, one or two short rows every two to three weeks – to keep them coming.

Radishes have a long sowing and growing season, with the first sowings made towards the end of winter if you have a protected space like a greenhouse or cold frame, and the final sowings made at the end of summer, or autumn in warmer climates. Check your Plant List in the Garden Planner to find out when to sow radishes in your location.

Winter Radishes

In fact, late summer is the ideal time to sow one of the Asian types of radish like daikon, mooli, or the really rather remarkable watermelon or ‘Mantanghong’ radish. And then there are the other winter radishes like the big black radishes, ensuring plenty to keep you interested as the growing season draws to an end. These slower but larger-growing radishes can be cooked as well as enjoyed fresh, and they’ll give a harvest through the autumn and into winter.

The deep, thrusting roots of daikon make them ideal for sowing as a winter green manure or cover crop because they will help to break up the soil while smothering weeds with their leaves.

All these larger types of radish need a little extra room compared to your standard salad radish, typically at least 3in (7cm) between plants, but be guided by the instructions on the seed packet because exact spacings will depend on the variety you’re growing.

There are lots of weird and wonderful varieties to try beyond the common red summer salad types. Daikons are definitely on my list for sowing later this summer as I’ve heard they’re also irresistible pickled – got to try that! Let me know what you hope to grow in the comments.

You can find radishes – even multisown ones – along with more than 200 other plants in our Garden Planner. It makes laying out and keeping a track of your garden a doddle, and it even has clever functions like the companion planting feature that helps you to fine-tune your planting. It’s a joy to use, but if you don’t believe me, try it for yourself. Start your free, seven day trial today, and don’t worry, there’s no need to put in any payment details.

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