How to Sow and Grow Courgettes: A Complete Guide
Courgettes, also called zucchini, are generous summer crops: one or two healthy plants can supply a household for weeks. They need warmth, rich soil, space and regular picking. Most disappointments come from planting out too early, allowing pots to dry, or leaving fruits to become marrows.
Choosing varieties
Green, yellow, striped and round-fruited courgettes are grown in much the same way. Compact varieties suit large containers, while trailing forms need more room. Choose a variety described as productive in your climate and start with two plants rather than filling the bed; mature leaves can spread more than a metre.
When and how to sow
Sow indoors three to four weeks before the last frost, usually in mid to late spring in cool climates. Fill 8–9 cm pots with peat-free seed compost, sow one seed 2 cm deep and keep at 18–24°C. Germination normally takes 5–10 days. Move seedlings into strong light as soon as they emerge and water only when the surface begins to dry.
In warm soil, seed can also be sown directly after frost risk has passed. Place two seeds at each station and remove the weaker seedling. Indoor sowing is more reliable where springs are cold or slugs are active.
Planting out
Harden seedlings for 7–10 days, then plant into a sunny, sheltered bed when nights are reliably mild. Enrich the soil with mature compost. Space bush plants 75–90 cm apart and do not bury the stem. A cloche can help initially, but remove it when flowering begins so pollinators can reach the flowers.
Growing in containers
Use one compact plant in a container of at least 40 litres with excellent drainage. Fill with peat-free multipurpose compost mixed with mature compost. Pots warm quickly but also dry quickly, so check moisture daily during hot weather.
Watering, mulching and feeding
Water deeply at the base, keeping leaves as dry as practical. Sudden changes from dry to saturated compost can check growth or damage fruit. Mulch after the ground warms. Once the first fruits begin to swell, use an organic high-potassium liquid feed every 10–14 days, following the label. Too much nitrogen creates huge leaves without improving cropping.
Flowers and pollination
Male flowers often appear before female flowers, so early blooms may fall without producing fruit. Female flowers have a tiny courgette behind the petals. Cool, wet or very hot weather can reduce bee activity. Grow flowers nearby and avoid spraying insecticides. If necessary, transfer pollen from a fresh male flower to female flowers with a soft brush.
Common problems
Small fruits rotting from the tip: usually poor pollination or cold weather; remove them cleanly.
Powdery mildew: improve airflow and avoid drought stress; older leaves are naturally more vulnerable.
Slugs and snails: protect transplants and keep hiding places around plants to a minimum.
Wilting: check soil moisture first; large leaves wilt temporarily in strong midday heat but should recover later.
Mosaic symptoms: remove badly distorted plants and control aphids through habitat and regular inspection.
Harvesting
Cut courgettes when they are about 10–20 cm long and still glossy. Pick three or more times a week in peak season. Use a knife and leave a short stalk; twisting can damage the plant. Overlooked fruits can be used as marrows, but removing them allows the plant to direct energy into new courgettes.
A reliable courgette routine
Wait for warm conditions, give each plant enough space, water steadily and inspect beneath the leaves every few days. Regular harvesting is the simplest way to keep production high.
