How to grow courgettes (zucchini) and summer squash

Give a courgette plant a warm spot, rich soil, plenty of water and a bee — and it will reward you generously. The golden rule: pick small and pick often.

Varieties — courgettes, zucchini and summer squash

Courgettes and zucchini are essentially the same vegetable — the difference is largely regional naming. Both are varieties of Cucurbita pepo grown for their fruit eaten while still immature and tender. Summer squash is the broader category that includes courgettes plus a range of other shapes — pattypan (flying-saucer-shaped), crookneck and yellow straightneck types.

• Green courgettes — the classic: 'Defender', 'Astia' (compact for containers), 'Romanesco' (ridged, pale green, superb flavour). All are highly productive.
• Yellow courgettes — 'Soleil', 'One Ball' (round, golf-ball sized, excellent flavour). Yellow varieties are identical to grow and offer variety on the plate.
• Pattypan or scallop squash — disc-shaped with scalloped edges, these are best harvested at 5–8 cm across when the skin is still tender. Varieties include 'Sunburst' (yellow) and 'Starship' (green). They grow on the same type of bush plant as courgettes.
• Round courgettes — 'Eight Ball' and similar round varieties are excellent stuffed whole when harvested at tennis-ball size.
• Compact or container varieties — 'Astia' and 'Bush Baby' are bred for large containers (at least 40 litres) and take up far less space than standard plants, making them an option for patio growers.

For a first attempt, any standard green or yellow courgette is an excellent choice. They're reliable, heavy-cropping and tolerant of slight neglect.

Space and site

The most common mistake new courgette growers make is underestimating how much space a plant needs. A courgette plant in full growth is a substantial thing — a bush of large, prickly leaves on thick hollow stems that can spread a metre or more in every direction. Cramping plants together causes poor air circulation, which accelerates powdery mildew and makes the centre of plants difficult to inspect and harvest.

• Allow a minimum of 90 cm to 1 metre between each plant, and ideally 120 cm for standard bush varieties.
• For two or three plants, you need a bed or patch of at least 2 square metres — more if you want space to move around them.
• A sunny or partially sunny position is needed. Courgettes tolerate light shade but fruit far less prolifically in it.
• Some varieties, particularly Tromboncino and some climbing types, can be trained up a trellis or wigwam of canes. This takes advantage of vertical space and improves air circulation around the fruit.

Starting from seed

Courgettes are fast growers and there's no need to sow them very early indoors. Sowing three to four weeks before your expected last frost date gives you well-established plants ready to go out at the right time. In cool temperate climates this might be mid to late spring; in warmer climates you may have flexibility to sow later or direct-sow outdoors.

Courgette seeds are large and easy to handle. Sow one seed per 9 cm pot, placed on its side rather than flat — this reduces the risk of the seed sitting in moisture and rotting before it can germinate. Use moist potting compost, cover with a thin layer of compost, and place somewhere warm — around 18–20°C is ideal for germination, which typically happens within five to ten days.

Keep seedlings in a bright position as soon as they emerge to prevent them from becoming leggy. Courgette seedlings grow quickly and the large seed leaves are obvious and unmistakable.

You can also direct-sow outdoors once the soil has warmed and all frost risk has passed — sow two or three seeds per station (planting position), then remove the weaker seedlings, leaving the strongest.

1. Sow one seed per 9 cm pot, on its side. Use moist compost and cover to about 1 cm depth. Place in warmth (18–20°C) to germinate.
2. Move immediately to bright light after germination. Courgette seedlings grow fast; insufficient light quickly leads to weak, elongated stems.
3. Harden off before planting out. Once all frost risk has passed, acclimatise plants to outdoor conditions over 7–10 days by placing outside during the day and bringing in at night.
4. Prepare a rich planting station. Dig a hole roughly the size of a bucket and fill with well-rotted compost or manure before back-filling and planting into the enriched spot.
5. Plant with correct spacing. Allow at least 90 cm to 1 metre between plants in all directions. They will grow much larger than they look at planting time.
6. Water in well and mulch. Give a thorough soak immediately after planting and apply a generous layer of compost or straw mulch to retain moisture and suppress weeds.

Rich soil and planting

Courgettes are hungry, thirsty plants that reward good soil preparation generously. They grow in a single season from seed to fruiting plant, and they do so at a remarkable pace — they need plenty of nutrition to fuel that growth.

• Well-rotted compost or manure dug into the planting hole at a generous rate is the best soil preparation. A 'station' approach works particularly well: dig a large hole, fill with a bucket or two of compost, replace some soil, then plant into this enriched spot.
• Good drainage is important. Courgettes need moisture but dislike sitting in waterlogged soil, which causes the base of stems to rot. Heavy clay soil should be improved with compost and grit, or growing in raised beds is advisable.
• pH: courgettes prefer a neutral to slightly acidic soil (roughly pH 6.0–7.0). Most garden soils are within this range without amendment.
• Container growing: compact varieties in large containers (40 litres or more) work reasonably well. Use a rich potting compost, water very frequently in warm weather, and feed weekly from the start of flowering.

Male and female flowers — and hand-pollination

Understanding the difference between male and female flowers on a courgette plant explains why fruit sometimes fails to develop and what you can do about it.

Courgettes produce separate male and female flowers on the same plant. Male flowers appear on a plain, thin stem. Female flowers are distinguished by a tiny miniature courgette at the base of the flower — this is the ovary that develops into fruit if the flower is pollinated. Male flowers typically appear first, before the plant begins producing females — this is normal and not a sign of a problem. Female flowers follow within a week or two.

In a garden with bees and other pollinators visiting freely, pollination usually happens naturally without any intervention. Problems arise when there are few pollinators — in a wet summer when bees are inactive, early in the season, or when plants are grown under cover.

Hand-pollination is easy and very effective:

• Identify an open male flower (no tiny fruit at its base) and an open female flower (with a tiny courgette at its base).
• Pick the male flower and peel back the petals to expose the pollen-covered central stamen.
• Dab the stamen directly onto the stigma — the central sticky structure inside the female flower. One male flower can pollinate several female flowers.
• Alternatively, use a small soft brush to transfer pollen from the male to the female flower.
• If you see female flowers opening without a male flower open at the same time, be patient — males will open soon. You can also pick a male flower while it's open, close it gently into a paper bag to preserve some pollen, and use it the next day.

Watering and feeding

Courgettes need significant and consistent moisture. Their large leaves lose a great deal of water through transpiration on warm days, and their rapid growth depends on a steady supply of both water and nutrients.

• Water at the base of the plant, directing water to the soil rather than over the leaves. Wet foliage promotes powdery mildew and can cause stem rot if water pools at the crown of the plant.
• Water deeply and regularly — a thorough watering two or three times a week in dry weather is better than daily shallow surface watering. Deep watering encourages roots to grow downward rather than near the surface, making the plant more resilient to dry spells.
• Mulching with compost, straw or wood chip significantly reduces water loss and is strongly recommended. Apply a generous layer around (but not touching) the crown of the plant after watering.
• Feeding: if you planted into good, well-composted soil, the plants may not need much additional feeding early on. Once the plant is in full flower and fruit production, a weekly liquid feed with a balanced or high-potassium fertiliser will keep it going strong through the rest of the season.

Harvesting small and often

This is the most important rule in courgette growing: harvest small and harvest often. A courgette left on the plant quickly becomes a marrow. Once a fruit reaches marrow size, the plant diverts its energy into maturing that one fruit and dramatically slows or stops producing new ones. The difference between a plant that is harvested regularly and one that is neglected for a week is remarkable.

• Check plants every day or every other day once fruit is forming — courgettes grow at an astonishing rate in warm, humid weather.
• Harvest most courgettes at 15–20 cm long. At this size they're at their sweetest and most tender, with small seeds and no need to peel.
• Round varieties are best at roughly the size of a tennis ball.
• Pattypan types should be harvested at 5–8 cm across, when the skin is still soft.
• Use a sharp knife or secateurs to cut the stem cleanly rather than pulling, which can damage the plant.
• The courgette flowers — both male and female — are edible and considered a delicacy. Stuff them with ricotta and herbs, dip in a light batter and fry, or add to salads. Pick male flowers freely; only harvest female flowers when you have plenty of males open for pollination.

Managing a courgette glut

Almost every courgette grower faces a glut at some point. When plants are in full production in warm summer weather, production can outpace consumption. This is not a crisis — there are plenty of ways to use the harvest.

• Freeze: slice into rounds or batons and blanch for 1–2 minutes in boiling water, cool in iced water, drain, and freeze in portions. Use from frozen in cooked dishes — they won't be crisp after freezing but are excellent in soups, stews, pasta sauces and risottos. Grated courgette freezes very well and can be portioned for use in courgette cake, fritters or sauces.
• Preserve: courgette relish and chutney use up large quantities and keep for months. See our food preservation guide for reliable recipes and methods.
• Cook differently: large courgettes that have escaped notice can be stuffed and baked, added to soups, roasted into a sauce, or spiralised into courgetti (zucchini noodles) as a pasta substitute.
• Share: leave a bag on your doorstep, take to a food bank, or offer to neighbours — most people are happy to receive fresh courgettes.
• Limit future planting: next season, plant fewer plants. One or two is often enough for a small family. Two well-spaced plants in great soil will out-produce five cramped ones every time.

For more ideas on using and preserving a vegetable harvest, see our guide to food preservation.

Common problems — mildew, slugs and more

• Powdery mildew: the most common courgette problem, causing a white or grey powdery coating on the upper surface of leaves. It almost always appears in late summer as temperatures fluctuate and humidity rises. It is cosmetic at first but spreads and weakens the plant over time. Good air circulation (correct spacing), watering at the base, removing affected leaves promptly and choosing resistant varieties all help. Some growers dilute milk 1:10 with water and spray affected leaves weekly — this can slow but not stop the spread. Accept that older leaves will get mildew late in the season; if the plant is still producing fruit, let it keep going.
• Slugs and snails on seedlings: young courgette seedlings and freshly transplanted plants are very vulnerable to slug damage, which can kill them overnight. Use copper tape around pots, apply a barrier of grit or sharp gravel around transplanted plants, go out after dark with a torch to collect slugs by hand, or use an iron phosphate-based slug bait that is safe around pets and wildlife. Once the plant is larger and has developed its prickly stems, it becomes far less vulnerable.
• Fruit rotting at the tip: typically caused by pollination failure (see the flowers section above). The fruit begins to develop but collapses without a successfully fertilised flower. Hand-pollinate to resolve this.
• Very few female flowers: early in the season, plants produce mainly male flowers. This is normal — be patient, females will follow. Excessive nitrogen in the soil can also promote leafy growth at the expense of flowering; avoid nitrogen-heavy fertilisers once the plant is established.
• Stem rot at the crown: caused by water pooling at the base of the stem. Water around the base of the plant, not into the crown. Good drainage and raised beds reduce the risk. Affected plants often cannot be saved.

Courgette-growing checklist

• Don't sow too early — three to four weeks before last frost date is plenty.
• Sow seeds on their side to reduce rotting before germination.
• Give each plant at least 90 cm of space — they're bigger than they look.
• Plant into a rich spot with plenty of well-rotted compost or manure.
• Mulch around plants to retain moisture and suppress weeds.
• Water deeply at the base — never over the foliage.
• Learn to distinguish male from female flowers; hand-pollinate if bees are scarce.
• Check plants daily in midsummer and pick fruit at 15–20 cm.
• Never let a courgette become a marrow on the plant — it stops production.
• Freeze, pickle or share surplus fruit to avoid waste.
• Protect seedlings from slugs — older plants can look after themselves.