Everything you need to know to grow your own cucumbers

Food writer Mark Diacono shares his tips on how to grow cucumbers and three of his favourite varieties to try.

My father was a meat-and-two-carbs kind of a guy, who was cursed in his rare liking of cucumbers, which reduced him to a chest-bashing hiccuper. It would have irritated him intensely that World Cucumber Day falls on his birthday in mid June.

Quite why it does—too late to sow and too early to harvest your own—is anyone’s guess, but it has become a handy reminder: after taking flowers to the old man’s grave, I check my plants. If they are growing well, I know I’m in for a good crop.

Cucumbers are about 95% water, but that remaining sliver does all the work. Choice of variety makes a huge difference to that 5% and the flavour and texture it provides. Indeed, the best homegrown varieties are so superior to those in the shops that they shouldn’t go by the same name.

Cucumbers fall into two main groups; greenhouse and outdoor types. Greenhouse varieties produce early and reliably in the warm conditions, but they prefer humidity—which tomatoes don’t—so you have a choice between growing either one or the other in a greenhouse or compromising optimal conditions for both.

Also, bear in mind that male flowers (those without a mini-fruit behind the bloom) have to be removed in the enclosed environment to prevent cross pollination, which can result in bitter, seed-filled fruit. Some greenhouse cucumbers (including ‘Merlin’, see below) have been bred to produce only female flowers, which saves this hassle.

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Outdoor cucumbers—also known as ridge cucumbers—are tolerant of cooler temperatures and usually do well in a sunny spot, but the harvest starts later in the season than for those grown undercover. They are typically shorter and squatter than their indoor cousins and the skin is usually ridged. Although some varieties will do well indoors or out, avoid growing outdoor cucumbers undercover alongside greenhouse varieties, as cross pollination is likely.

I tend to grow three delicious, reliable varieties a year. Without exception, ‘Crystal Lemon’—an outdoor variety that also thrives undercover—is one of them. The yellow and almost spherical fruits, easily mistaken for lemons if your specs need a clean, are as beautiful as they are delicious. Their flesh seems to be cool, no matter how hot the summer, and there’s no hint of a bitter aftertaste.

This year, I’m going to grow a greenhouse variety called ‘Merlin’, with its promise of a very high yield as it produces only female flowers that might all develop into fruit. The smooth, crisp and juicy cucumbers reach a maximum of 6in. It also has good resistance to the three likeliest cucumber nuisances: powdery mildew, downy mildew and cucumber mosaic virus. It does best undercover, but is a fair gamble in the sunniest spot outdoors.

‘Goblin’ is this year’s third variety; a compact cucumber that can easily produce 50 fruits despite its size. Great for container growing, ‘Goblin’ has very good disease resistance and its smaller fruit are perfect for pickling.

Cucumbers should be started off undercover in small pots in March and April. I’ve found most success with placing the seed pointing upwards, as those sown on their side rot more frequently. They need warmth to germinate: a heated propagator or a sunny, warm window sill works well. You can use the airing cupboard, but bring the seedlings into the light at the first sign of growth.

Pot them on when they reach a good size for the pot. If you are growing cucumbers outside, give them the sunniest, most sheltered spot you have, hardening them off properly before planting out after the frosts have gone. Indoors or out, allow 20in or so between plants.

Cucumbers are scrambling plants and, although you can let them creep across the ground, tying them into a cane tepee gives them something to wind around, which lifts the fruit and leaves off the floor and thus reduces the likelihood of fungal disease, as well as making the harvest easier.

Steady watering is ideal: little and often, rather than deluge and drought, and take care to water the ground, not the plant. A fortnightly high-potassium feed—liquid tomato or seaweed feed is excellent—from flowering onwards will boost the health and heft of your crop. Harvesting depends on variety: pick them at the size the packet indicates and it’ll encourage more to follow.

If you are reminded by World Cucumber Day that you have left it too late to sow cucumbers, you should be able to get seedlings online from somewhere such as www.rocketgardens.co.uk and be in crisp cucumbers by August.

Mark Diacono grows edibles, both usual and unusual, at Otter Farm in Devon (www.otterfarm.co.uk). His new book, From Scratch: Ferment (Quadrille, £12.99), is out now