This Allotment Pro editorial draft summarises the cited RHS guide. Check the source and adjust timings for local conditions.RHS source guide
Pot sow — Sow one seed on its side, 13mm (½in) deep, in a 7.5cm (3in) pot at 18–21°C (65–70°F)
Direct sow — Once soil is warm, sow two or three seeds 2.5cm (1in) deep at sites at least 90cm (3ft) apart, thinning to the strongest seedling
Transplant — Harden off well-rooted plants after frost, then set them at least 90cm (3ft) apart in rich prepared soil
Pick — Cut fruits frequently at 10–12.5cm (4–5in) long to prolong cropping
Courgettes, or zucchini, are tender Cucurbita pepo plants that grow vigorously and crop abundantly through summer. In good weather, one plant can produce three or four fruits each week. Starting seed indoors in spring gives the longest season, with young plants moved outside in early summer after frost.
Provide warmth, full sun, shelter, rich soil and regular water. A typical plant needs roughly one square metre of ground. Where space is limited, train a climbing cultivar vertically or choose a compact bush type for a large container or growing bag.
Fruits may be green or yellow, striped or plain, long or rounded. They are edible at many sizes, but their flavour and texture are best when picked small. Regular cutting encourages more fruits; neglected courgettes quickly expand into marrows. Male flowers are edible too and can be harvested without reducing the crop.
Choose trailing plants for generous open ground, compact bush cultivars for small plots or containers, and climbing selections for vertical training. Fruit colour ranges from pale or dark green to golden yellow, with cylindrical, slim or spherical shapes. Leaves may be green, mottled or naturally silvery.
Spineless stems make frequent harvesting more comfortable. In damp or humid districts, disease-resistant cultivars can remain productive longer. RHS Award of Garden Merit cultivars have performed reliably in trials. Seed offers the widest choice, while young plants bought in late spring or early summer save time but are available in fewer varieties.
An early cultivar producing tasty cylindrical courgettes with conspicuous golden-yellow skin.
A popular, dependable cultivar producing a large crop over a long season when fruits are picked regularly.
A prolific cropper with an open plant habit that exposes the fruits and makes frequent picking easier.
A French cultivar bearing pale-green fruits with a sweet delicate flavour from July to October.
A spineless cultivar producing large straight dark-green fruits, with useful performance in cool or exposed sites.
A compact plant suited to large containers, producing a heavy crop of slim uniform courgettes. ## 3 - Preparing The Ground Choose a warm sunny position where bush plants can stand at least 90cm (3ft) apart. Courgettes make broad leaves and need room to sprawl without shading one another. Several weeks before sowing or planting, enrich each site with garden compost or well-rotted manure over an area about the width and depth of a spade blade. This local reservoir of organic matter supports vigorous growth and helps moisture remain available. Let disturbed soil settle before planting. For a no-dig bed, spread a generous organic mulch over each intended site and plant through it. Mark centres before growth hides the ground, maintaining the same 90cm (3ft) minimum spacing.
Choose a warm sunny position where bush plants can stand at least 90cm (3ft) apart. Courgettes make broad leaves and need room to sprawl without shading one another.
Several weeks before sowing or planting, enrich each site with garden compost or well-rotted manure over an area about the width and depth of a spade blade. This local reservoir of organic matter supports vigorous growth and helps moisture remain available. Let disturbed soil settle before planting.
For a no-dig bed, spread a generous organic mulch over each intended site and plant through it. Mark centres before growth hides the ground, maintaining the same 90cm (3ft) minimum spacing.
Choose a compact or bush cultivar and a container at least 45cm (18in) wide. One plant fills a pot of that size. A growing bag can support one, or sometimes two, compact plants if watering and feeding are maintained.
Indoor sowing in mid- to late spring gives earlier, more reliable germination and keeps seedlings away from slugs. Direct sowing in early summer is practical in warm districts once the soil has heated.
In April or early May, sow each large flat seed on its side, 13mm (½in) deep, in a 7.5cm (3in) pot or individual module of moist peat-free seed compost. Sideways sowing helps water drain from the seed rather than collecting on it.
Place pots in a heated propagator, or on a sunny windowsill under a clear lid or polythene bag. Maintain 18–21°C (65–70°F) for germination. As soon as shoots appear, remove the propagator cover or bag and give seedlings bright light so they grow sturdily.
In late May or early June, prepare individual stations once the soil is warm. Sow two or three seeds 2.5cm (1in) deep at least 90cm (3ft) apart, positioning each station centrally so the eventual plant can spread in every direction.
Water well and cover with a cloche or plastic-free fleece. Leave protection in place for as long as practical after germination. If several seedlings emerge, remove the weaker plants and retain only the strongest. Outdoor seedlings crop later and need particular protection from slugs and snails.
Indoor-raised courgettes are ready to plant in early summer when well rooted and after the soil warms. Harden them off gradually and wait until frost risk has passed. Prepare the rich planting sites in advance.
Slide each root ball carefully from its pot without disturbance, plant it in the centre of a prepared station and keep at least 90cm (3ft) between plants. Firm gently, water thoroughly and protect tender new foliage from slugs and snails.
Place a compact or bush cultivar in a warm sunny position. Fill a container at least 45cm (18in) wide with peat-free soil-based or multi-purpose compost and plant one courgette centrally. Water it in and continue watering regularly. Growing bags can hold one or two compact plants.
Avoid overcrowding: broad leaves evaporate large quantities of water, and dense growth makes harvesting and disease inspection harder.
Courgettes grow fast and require reliable moisture, especially while fruiting. Containers need the closest attention because their compost dries rapidly.
Keep soil or compost consistently moist. In hot weather, daily watering may be needed. Direct water to the base rather than wetting leaves, which can encourage fungal disease. Water early in the morning or in the evening so less is lost to evaporation, using collected rainwater where possible.
For ground-grown plants, sink a 15cm (6in) pot beside the roots and pour water into it. This carries moisture downward while keeping the plant neck drier and less prone to rot.
Spread a thick layer of garden compost or well-rotted manure over damp soil to conserve moisture and suppress weeds. Leave a clear gap around the main stem so organic material does not hold water against the neck.
When the first fruits begin to swell, feed container courgettes every 10–14 days with a high-potash liquid fertiliser. Plants in well-prepared ground normally need no supplementary feed unless the soil is poor.
Cool early-summer weather may limit pollinating insects, so flowers can fail to set or tiny fruits may rot. This generally resolves as conditions warm. Keep flowers accessible to insects and avoid damaging the central growing area during watering or harvesting.
Remove leaves that become tatty or heavily affected by powdery mildew. Selective removal exposes fruits to sunlight, makes them easier to find and improves airflow, but retain plenty of healthy foliage to power the crop.
Climbing cultivars can be guided up strong canes or wires to save ground space. Tie or support the main growth carefully as it lengthens, checking that the weight of leaves and fruit remains secure.
Do not confuse natural pale silver leaf markings with mildew. Powdery mildew appears as a spreading dusty coating and may be accompanied by declining foliage.
Cut courgettes while tender and full flavoured, ideally at 10–12.5cm (4–5in) long. Use secateurs or a sharp knife to make a clean cut without twisting or damaging the brittle plant. In good weather, check plants several times each week because fruits enlarge quickly.
Regular small harvests maintain a long cropping period and can yield three or four fruits per plant each week. Search beneath large leaves so no courgette grows unnoticed into a marrow.
Courgette flowers can be added to salads, fried or stuffed. Prefer male flowers, which stand on plain stalks without a small fruit behind them, so harvesting does not reduce the developing crop. Leave enough flowers for pollination and wildlife.
Courgettes are tender and susceptible to frost. Cool conditions can cause poor pollination, fruit-set failure or tiny fruits that rot, but later warm weather usually restores cropping. Slugs and snails attack seedlings, flowers and young fruit, while damp foliage encourages fungal disease.
Poor fruit set, misshapen or rotting young fruits and leaf symptoms can result from weather, pollination, watering or disease. Diagnose the pattern before altering care.
Problem sourceYellowed or discoloured leaf patches with growth beneath the foliage can reduce plant vigour and cropping. Improve airflow and avoid prolonged leaf wetness.
Problem sourceSoft decaying tissue with fuzzy grey fungal growth is encouraged by damp, damaged or crowded plants. Remove affected material and keep air moving through the canopy. Source: Royal Horticultural Society. Structured as an Allotment Pro editorial draft for review; source facts and links remain attributable to the publisher.
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