Sow courgettes in late April and you'll be picking by July

Late April is the best time to sow courgettes indoors. Plants sown then are ready to go out in mid to late May, just after the last frosts, and you’ll be picking from late June or early July.

The full window runs from late March to late April indoors, or early May to early June if you sow straight into the ground. Courgettes are fast, so there’s no prize for starting early.

Sowing indoors

Sow one seed per 8 cm pot, 2.5 cm deep, with the seed on its edge so water runs off rather than sitting on the flat face. Keep the pots somewhere warm, such as a windowsill or heated propagator, and they’ll come up in about a week.

Plants sown in late March grow quickly and can outgrow their pots before it’s safe to plant them out. If that happens, move them into a 1 litre pot. Most people find a sowing in mid to late April easier to manage.

Planting out

Courgettes are killed by frost, so plant out from early to late May, after a week of hardening off. The dates here are for a typical lowland garden in England or Wales, where the last frost is usually around 20 April. In Scotland, the north of England and frost pockets, wait until the end of May or early June. In the south-west and in cities you can usually start in early May.

Each plant spreads to around a metre across, so give them space:

1. Dig a hole about a spade deep and wide, and fill it with compost or well-rotted manure. Courgettes are hungry plants.
2. Plant so the top of the rootball is level with the soil, or very slightly below.
3. Leave 90 cm between plants each way.
4. Water well, and keep fleece handy for a cold night in the first couple of weeks.

Sowing outdoors

From early May you can sow straight into the soil where the plants will grow. Sow two seeds 2.5 cm deep at each spot, cover with a jam jar or cloche to warm the soil, and remove the weaker seedling if both come up. Outdoor sowings start cropping a couple of weeks later than transplants but are less work.

Watering and feeding

Courgettes need a lot of water once they’re cropping. Water at the base, not over the leaves, about twice a week in dry weather, and more on light, sandy soil. Once the first fruits form, a liquid tomato feed every couple of weeks keeps them going.

Nasturtiums, marigolds and sweetcorn grow well alongside. Keep courgettes away from potatoes.

Picking

The first courgettes usually come 35 to 50 days after planting out, and plants keep producing for about 12 weeks. Pick them at about 15 cm, every couple of days in summer. Leave one for a week and it becomes a marrow, and the plant slows down.

Common problems

Powdery mildew. A white coating on the leaves from mid-summer onwards, worse when the roots are dry. Water regularly and remove the worst leaves. It rarely stops plants cropping.

Fruit rotting at the tip. Often the old flower holding damp against the fruit, or poor pollination in cold, wet weather. Pick off affected fruit, and the next ones are usually fine.

Lots of flowers, no fruit. The first flowers on a young plant are often all male. Female flowers, with a tiny courgette behind them, follow within a week or two.

Slugs. Young plants are easy targets. Plant out sturdy plants rather than small ones.

See all the windows on the courgette page. If space is tight, a courgette takes up four squares in square foot gardening.