Growing Courgettes in Scotland: The Complete Guide

Cucurbita pepo

Everything you need to grow courgettes in Scotland, from an April sowing on a windowsill to picking three or four fruits a week in August. We have done the research so you don't have to.

Courgettes are the crop that divides Scottish summers. In a good year one plant will bury you in fruit. In a cold wet one the flowers drop and the tiny fruits rot before they get started. They are tender, hungry, and need warmth, three things our climate does not reliably provide. The trick is not the variety. It is the start. Sow indoors, plant out late, give them the sunniest sheltered spot you have, and keep the water coming. Get those things right and a courgette plant in August earns its square metre of ground many times over.

Why courgettes need a head start in Scotland

Courgettes are not hardy. They need 18 to 21°C to germinate and a warm soil to thrive. A cold check after planting out sets them back badly, and a plant that is struggling in June rarely catches up. The answer is to start them indoors in April or early May and keep them under cover until the soil has genuinely warmed. In much of Scotland that means late May on the mildest coasts and June elsewhere.

In a cold summer the fruit may rot when small. The female flowers have not been properly pollinated and the tiny courgettes behind them yellow and drop off. This is frustrating but temporary. Once the weather improves and the bees are out, the problem sorts itself. A plant that gets through those first weeks will usually recover and crop well.

Varieties

Growing conditions matter far more than variety name here: warmth, shelter and regular water will crop any of these regardless. All carry the RHS Award of Garden Merit, a UK-wide award, not a Scottish one.

Also worth considering

Soil and site

Courgettes want a warm, sunny, sheltered position. They form large vigorous plants and need about a square metre of ground each. Dig a generous amount of garden compost or well-rotted manure into each planting site, roughly the depth and width of a spade's blade, a few weeks before planting, to let the soil settle.

Climbing varieties can be trained up canes or wires. Compact bush varieties suit containers: use a pot at least 45cm wide filled with soil-based or multipurpose compost. Growing bags also work for one or two compact plants.

Sowing and planting

Sow indoors in April or early May. Sow one seed per 7.5cm pot, on its side, about 13mm deep, in moist peat-free seed compost. The seeds need 18 to 21°C to germinate. A heated propagator or a sunny windowsill under a clear lid does the job. Once the seedlings appear, take them out of the propagator. Grow them on in good light, and harden them off before planting out.

Plant out in early summer, once the soil has warmed. Space plants at least 90cm apart. Remove each young plant carefully from its pot without disturbing the roots, plant into the centre of your prepared site, firm in gently, and water well. Protect from slugs and snails.

You can also sow directly outdoors in late May or early June in warmer regions. Sow two or three seeds 2.5cm deep at each site and thin to the strongest seedling. Cover with a cloche or fleece. Outdoor sowings usually crop later than indoor-raised plants.

Watering and feeding

Courgettes are thirsty plants and need regular watering, especially while fruiting. Keep the soil consistently moist. During hot weather they may need watering daily. Water the soil, not the leaves. Wet foliage encourages powdery mildew.

The best watering trick for courgettes is to sink a 15cm pot into the ground next to each plant and water into that. The water goes straight to the roots and does not sit around the neck of the plant, which can cause rotting. Use rainwater when you can.

Lay a thick mulch of garden compost or well-rotted manure around the plants, but leave a gap around the stem. Plants in the ground rarely need feeding unless the soil is poor. Feed container plants every 10 to 14 days with a high potash liquid fertiliser once the first fruits start to swell.

Keeping them productive

Remove any leaves that become tatty or affected by powdery mildew. This exposes the fruit to the sun, helps ripening, and makes finding the courgettes easier when you harvest. A plant with a tangle of leaves is a plant hiding a marrow.

Harvesting

Harvest courgettes when they are 10 to 12.5cm long. At this size they are tender, full of flavour, and the plant will keep producing. Use secateurs for a clean cut. Twisting or pulling damages the plant. Pick regularly, every day or two in a good summer. A plant that is picked clean keeps cropping. One left with a swelling fruit shuts down, and a marrow takes a lot of plant energy that would otherwise go into more small courgettes.

You can also harvest the flowers. Pick the male flowers, the ones without a small fruit swelling behind them, and leave the female flowers to set fruit. The flowers add colour to salads, or you can fry them or stuff them with soft cheese. In a good summer you can expect three or four fruits a week from a single plant.

Common problems

• Fruit rotting when small. Poor pollination in cold or wet weather. The female flowers are not being pollinated. Usually temporary. Once the weather improves and bees are active, the problem sorts itself.
• Slugs and snails will eat young plants, flowers and small fruits. Protect young plants and keep the surrounding area clear.
• Powdery mildew appears as a white dusty coating on the leaves. Remove affected leaves, water the soil rather than the foliage, and space plants well so air can circulate. It is unsightly rather than fatal.
• Grey mould is a fuzzy grey fungus, usually in cool humid conditions. Good spacing, removing dead leaves, and watering the soil not the leaves all reduce the risk.
• No fruit at all. The plant is too cold or was planted out too early. Courgettes need warmth to set fruit. A late start indoors and a warm sheltered spot fix this next year.

Common questions

Sources