How to grow radishes in pots and small spaces

Radishes are the crop I'd hand to anybody who thinks they can't grow things, because they go from seed to something you can eat in about four weeks, and they'll do it in a pot on a balcony as readily as in a bed. They ask for very little. What they will not forgive is being left in the ground too long, or being fed like a leafy crop, and those two between them account for nearly every disappointing row.

When to sow here

Radishes will go in through most of the year, and they're at their best in the cooler half of it. Sow from about February through to November and you'll get good ones. Sown into the heat of midsummer they bolt, and a bolted radish is hot, hollow and woody rather than crisp, so that's the stretch to skip or at least to grow in afternoon shade.

Where to put them

They want 4 to 6 hours of sun, which makes them one of the more forgiving crops for a spot that gets shaded for part of the day. Anything with drainage holes will do as a container, and depth is the only real requirement. Allow 15cm for a round radish and closer to 30cm if you're growing an oriental or daikon type, which goes down a long way further than people expect.

Loose soil matters more than rich soil. A radish swells sideways as well as down, and in compacted ground it simply can't, so it stays small and stringy. Break the soil up properly first, or use a potting mix in a container.

Sowing

Seed goes straight in, because radishes resent being transplanted and there's no point anyway when they're this quick. Sow about 2cm apart and cover lightly, around 1cm deep, then water gently so you don't wash the seed into a clump.

Then thin them once the seedlings are up, and this is the step everyone skips. Radishes left crowded make tops and no bulb, because each one is competing for the space it needs to swell. Pull the weakest out and leave the rest about 5cm apart, and eat the thinnings in a salad.

Water properly rather than often

Even moisture is what you're after, because a radish that dries out and then gets watered heavily will split, and one that stays dry goes hot and woody. A daily splash is not the answer, despite how often it gets recommended, because it wets the top centimetre and leaves the root zone dry underneath. Give the pot or the row a proper soak so the water reaches the bottom of the roots, then check with a finger and soak it again when the top few centimetres have dried out. In hot weather that might be daily, and in spring it might be twice a week.

Why you get leaves and no radish

It's the most common complaint about this crop, so it's worth being specific. Too much nitrogen is the usual cause, because a bed that's been recently fed with a high nitrogen fertiliser tells the plant to make leaf, and a radish that's making leaf is not making a bulb. Crowding is the second cause and heat is the third. Radishes want soil in reasonable condition rather than freshly fed soil, so put them in after the hungry crops rather than before.

Pulling them

Watch for the shoulder of the radish pushing up out of the soil, and start pulling when they're about marble sized. If you leave them another week to get bigger, which is exactly what everybody does, that's usually the week they go pithy. Pull one and taste it, and let that decide the rest of the row.

And eat the tops. Radish leaves are perfectly good wilted into something with a bit of garlic, and most of them go in the bin for no reason.

Keep it going

Sow a short row every fortnight rather than the whole packet at once. Forty radishes in one week is a lot of radish, and four radishes a week for ten weeks is dinner. They also work well sown between slower crops like carrots or lettuce, because they're up and out before the slow ones need the room.

Shop related products

• Brunnings Seed Raising Mix 5L. A fine mix over the top of the row so small seed gets good soil contact.
• Brunnings Ultimate Garden Soil 30L. For loosening up a bed that is too tight for a root crop.
• D.T. Brown Lettuce All Year, 750 seed pack. Radishes sown between the lettuce are up and out before the lettuce needs the space.
• Easy Wetta Garden Mulch 50L. Mulch between the rows keeps the moisture even, which is the whole trick with radishes.

Did you know we stock radish seed loose by the variety in the shop, with Cherry Belle, French Breakfast, Sparkler and an oriental radish on the rack, along with potting mixes and pots with saucers. The loose seed isn't on the website, so give us a ring on (08) 8536 4333 to check what's on the shelf, or come and pick a couple of varieties in the garden centre.

More from the Homegrown Delights blog

• How to grow baby vegetables, and when to pick them
• How to grow carrots, and when to sow them here
• How to grow vegetables on a balcony or patio

Radishes are the only crop where being impatient is an advantage, which is probably why I'm reasonable at them.

Candeece