How to grow courgettes

Courgette varieties

There are numerous excellent courgette varieties to try, including those producing round or yellow fruit: Defender, Eight Ball (round), Gold Rush (yellow), One Ball (round and yellow), Parador, Sunburst (yellow), Tondo di Chiario Nizza, Zucchini.

What you’ll need to start growing courgettes

You don’t need much equipment to grow courgettes. Here are the basics:

• Garden fork and spade
• Trowel
• Well-rotted farmyard manure
• General purpose fertiliser
• High potassium fertiliser
• Courgette seeds

For indoor sowing:

• 9cm (3.5in) pots
• Seed sowing compost
• Propagator (optional)

Cultivating courgettes

Courgettes need a sheltered position in full sun and a fertile soil that holds plenty of moisture. They are reasonably large plants, so need plenty of room, spacing them up to 90cm (3ft) apart. Some more compact varieties are also available - and these are also best suited for growing in containers.

For best results, they can be grown in planting pockets. Roughly 2 to 3 weeks before sowing seed or planting out, dig a hole 30cm (12in) square and deep and fill with a mixture of compost or well-rotted manure and soil. Leave a low mound at the top and sprinkle a general feed over the soil.

As courgettes need plenty of water, a top tip is to sink a 15cm (6in) pot alongside them when planting out. Watering into the pot ensures the water goes down to the roots and doesn't sit around the neck of the plant, which can lead to rotting. It also keeps it off the foliage, which helps reduce problems with powdery mildew.

Sowing courgettes

For the best results, sow the seeds indoors from mid to late April 13mm (½in) deep individually in 7-9cm (3-3½in) pots filled with peat free compost.

Sow the seed on its side as this helps prevent water pooling on the top. Place the pots in a propagator or other warm place at 18-21°C (65-70°F) and as soon as the seeds germinate, take any cover off.Harden off the young plants for 7-10 days before planting outside in late May/early June after the last frosts have passed.

Outside, sow 2 or 3 seeds 2.5cm (1in) deep in the planting pocket in late May or early June and cover with a cloche Thin the young seedlings to leave just the strongest one.

How to care for courgettes

As the young plants are susceptible to frost and cold weather, cover them with fleece or a cloche if the weather turns cold.

Keep the plant well watered making sure to water around the base not the leaves. And try to water deeply every few days rather than little and often. Keep the soil constantly moist by watering the soil around the plants - not over them - whenever needed. Once the first fruit starts to swell, feed every 10-14 days with a high potassium feed.

Harvesting courgettes

Harvest courgettes when they are fairly small, about 10-12.5cm (4-5in) long. Regular picking when they are small ensures a long cropping period over several months. If you want a few marrows then let them grow on but mainly they are tastier when small.

Courgettes produce large crops, so one or two plants is all that’s needed to feed a large family.

Common pests, diseases and problems of courgette plants

Powdery mildew

Powdery mildew on courgettes can be a common problem. This is a fungal disease that appears as a white powdery deposit on the leaves, stunting growth and causing leaves to shrivel. Drought-stressed plants are more susceptible.

• Dig organic material into the soil before planting to improve soil water retention.
• Space plants when planting to ensure good air circulation.
• Remove any affected growth promptly.
• Water regularly in dry periods and try not to get the leaves wet.

Yellow courgette leaves

Older courgette leaves often turn yellow and drop off the plant. This is not a cause for concern as they will be replaced by new growth, but also see Cucumber mosaic virus.

Cucumber mosaic virus

Courgette leaves turning yellow can also be due to cucumber mosaic virus. This causes deformed, stunted leaves with a characteristic ‘mosaic’ yellow patterning. Affected plants produce few or no flowers, and any fruit that develop are small and inedible.

• Remove and destroy affected plants promptly.
• Wash hands and tools after handling affected plants.
• Plant disease-resistant varieties.
• No chemical controls are available.

Grey mould/botrytis mould

Grey mould is a fungal disease that appears as powdery grey mould at the stalk of courgette, gradually covering the whole fruit, which then rots.

• Remove any dead leaves or flowers.
• Remove any affected fruit promptly.
• Space plants well when planting to allow good air circulation.
• There are no chemical controls available for grey mould.

Courgettes rotting when small or not setting

Courgette fruits can appear to start swelling but then rot or drop off the plant while still small. This occurs when the flowers are not pollinated, and is usually more of a problem early in the season. If the problem persists, hand-pollinate flowers using a small paintbrush.

Slugs and snails

Slugs and snails will eat the leaves of young courgette plants, and can be identified by the slime trails that they leave, as well as the damage they do.

• Check plants at night and remove slugs and snails by hand.
• Covering the soil around plants with crushed eggshells or a grit barrier.
• Scatter environmentally-friendly slug pellets if other methods are not sufficient.

Key features of courgettes