When to plant courgettes?
Sow courgettes indoors at 18-21 °C: in April or early May in the north and centre, and earlier in the south only if you can hold that warmth. They go outside once frost has passed and nights stay above 15 °C, about 90 cm apart.
When, by region
| North | Centre | South | |
|---|---|---|---|
| Sow indoors | April or early May, at 18-21 °C. One seed on its side, 13 mm deep, in a 7.5 cm pot. | As in the north. | Before April only if you can hold 18-21 °C. Without heat, April. |
| Outdoors | Once frost has passed and nights stay above 15 °C. Direct sow in late May or early June, 2.5 cm deep, or plant out in early summer. Higher up, wait. | The same thresholds, usually sooner than in the mountains. Umbria's guide does not fix a month. | In Campania the crop is usually protected or half-forced: the cover stays until nights are above 15 °C. In Sicily, in the open ground, you can sow or transplant. |
Thresholds from the RHS and Campania. The month matters less than frost and the nights.
April or early May indoors, the 18-21 °C, seed on its side at 13 mm, late May or early June outdoors, and the 90 cm spacing, are from the RHS. The 18-24 °C optimum, growth stopping at 10-13 °C, and covers kept on until nights stay above 15 °C, are from Campania's guide; Sicily gives the same temperatures. Umbria's integrated-production guide does not name a sowing month. Nearby months are in the April calendar, May and June, and the wider picture is the planting calendar.
A short spell indoors, or direct sowing
The RHS starts courgettes indoors in April or early May, one seed per pot, and moves them outside in early summer, once the soil has warmed, after hardening them off. The seed goes in on its side. Outdoors, in late May or early June, sow two or three seeds 2.5 cm (1 in) deep and keep the strongest plant. The pot method is in the homemade seedbed.
In Campania, under a tunnel, direct sowing is allowed but not advised: transplant. In Sicily, in the open ground, either is fine. Below 10-13 °C (50-55 °F) growth stops. A frosty night stops the plants even after a mild day.
Spacing and pots
The RHS leaves at least 90 cm (3 ft) between plants: one plant takes about a square metre. In Campania, bush varieties go 100-120 cm between rows and along the row, about 0.8 plants per square metre; upright varieties, and crops under a tunnel, go up to 1.5-2. In Sicily, under cover, the guide suggests 1 m between rows and 0.5 m along the row. In the open ground, 1.5-2 m between rows and 1-1.3 plants per square metre. In a home garden the RHS 90 cm lets air through.
In a pot, one compact plant in a container at least 45 cm (18 in) wide, in sun and out of the wind. On a balcony the compost can dry out in a hot day: see the container garden. Once the first fruits swell, in a pot, the RHS suggests a high-potassium liquid feed every 10-14 days. In enriched ground you often need less.
Water, flowers, mildew
Water the soil, not the leaves. The RHS says water on the leaves encourages fungi, including powdery mildew, and that thirsty plants get it more. In Umbria the crop is most sensitive to drought at flowering and while the fruit swells; too much water brings root rots. How much is in watering. A layer of garden compost or well-rotted manure holds moisture, with a gap around the stem: that is mulching.
In the cool of early summer, tiny fruits can rot: the RHS puts that down to cold weather and poor pollination, and says it rights itself once the weather improves. The flowers need insects. Pick the fruit small, at 10-12.5 cm (4-5 in): leave it, and it becomes a marrow and the plant slows. In good weather the RHS gives three or four fruits a week from one plant.
The white dust on the leaves is courgette powdery mildew, under pests and diseases. A dark patch only on the tip of the fruit, after uneven watering, is the same disorder as blossom end rot. Don't repeat cucurbits too often in the same spot: that is in crop rotation.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
Can I sow courgettes in March?
Not in the open ground. Indoors, the RHS starts in April or early May, at 18-21 °C. Earlier, and so in March, only if you can hold that temperature. Below 10-13 °C, growth stops.
When do they go outside?
Once frost has passed and nights stay above 15 °C. In the north, higher up, that is often later than on the valley floor. In Campania the tunnel cover stays until nights clear that threshold.
How far apart?
The RHS says at least 90 cm (3 ft). In Campania, bush varieties go 100-120 cm apart. One plant fits a pot at least 45 cm wide.
Why do tiny fruits rot?
In early summer, while it is still cool, the RHS links it to cold weather and poor fruit set. It usually rights itself once the days warm up. The flowers need pollinating.
Does powdery mildew spoil the courgettes?
It hits the leaves, not the fruit directly. Limit it with resistant varieties, water at the base and air between the plants. Pick the fruit small and firm.