Cucurbit

What counts as a cucurbit

Cucurbits are the squash family (Cucurbitaceae) — a group of sprawling, fast-growing plants grown for their fleshy fruit. In a UK garden the ones you're most likely to meet are:

• Courgettes and marrows — the easiest and most generous of the lot
• Cucumbers — both greenhouse and outdoor (ridge) types
• Pumpkins and winter squash — the big trailing kinds for autumn storage
• Summer squash — patty pans and crooknecks
• Melons — the fussiest, needing real warmth to ripen here

Once you've grown one, the family resemblance is obvious: big leaves, hollow trailing stems, and bright yellow flowers.

Shared traits

Cucurbits all behave in much the same way, which makes the whole family easy to understand at once.

They are tender. Frost kills them outright, so there's no rushing them outside. Sow indoors in April or May, keep them warm, and plant out only once the nights have settled — late May or early June in most of the UK. A cold snap in a chilly spring can check them badly, so don't be in a hurry.

They are hungry and thirsty. Cucurbits are greedy feeders that want rich, moisture-holding soil — a planting hole stuffed with compost or well-rotted manure pays off all season. They drink a lot, too. Water deeply and regularly at the base, especially once the fruit starts to swell; let them dry out and you get bitter cucumbers and stunted courgettes.

Male and female flowers

Here's the quirk that catches beginners out: cucurbits carry separate male and female flowers on the same plant. The males come first and simply provide pollen. The females have a tiny embryonic fruit — a miniature courgette or pumpkin — already formed behind the bloom. Only the female flowers go on to make a crop.

Most cucurbits are insect-pollinated, relying on bees to carry pollen from male to female flowers. In a cool, wet UK summer, or early in the season before the bees are busy, that pollination can fail — the little fruits start to swell, then yellow and rot off. If that happens you can hand-pollinate: pick a male flower, peel back its petals, and dab it into the centre of a female. Some F1 hybrid cucumbers are all-female, which sidesteps the problem and avoids bitter fruit.

Shared pests and problems

Because they're one family, cucurbits share their troubles. Slugs and snails love seedlings and young plants and can demolish them overnight. Powdery mildew — a white dusty coating on the leaves — is almost guaranteed by late summer, especially on dry-rooted plants; keeping them well watered slows it down. Greenhouse cucumbers can also pick up red spider mite and aphids in hot, dry conditions.

For a forgiving first cucurbit, start with courgettes — one or two plants are usually plenty. See our guide to growing pumpkins and squash for sowing dates and spacing.