Zucchini is simply the American name for courgette. Whatever you call it, this is one of the most generous vegetables you can grow in a British garden. One healthy plant can produce several fruits a week in warm summer weather. The difficulty is keeping it supplied with water, space and pollination, then picking before the fruits turn into enormous marrows.
Pick a variety that suits your garden
Most courgette plants grow as vigorous bushes, although some varieties trail and can be trained up supports. A compact bush variety is best for a large patio container or small vegetable bed.
Fruits may be green, yellow, striped, round or elongated. The flavour differences can be subtle, so consider disease resistance and how easy the plant is to harvest. Open-growing varieties let you spot developing fruits without rummaging through prickly foliage.
The RHS recommends giving ordinary plants roughly one square metre of growing space. If you only have a small raised bed, one well-grown plant is often more practical than crowding three into it.
When to start zucchini seeds
In Britain, courgettes are usually sown indoors in April or early May for planting out after frost risk has passed. Seeds need warmth to germinate; the RHS advises around 18–21°C.
Sow each seed separately into a small pot of moist peat-free seed compost, about 1.5cm deep. Label the variety and keep the compost gently moist.
Once shoots appear, move seedlings into strong light. A warm windowsill without enough sunlight produces long, weak plants. Don't keep them indoors for weeks in tiny pots once roots have filled the compost.
You can also direct-sow outdoors from late May or early June if the soil has warmed sufficiently. Outdoor seedlings are more vulnerable to slugs and snails.
When can zucchini plants go outside?
Courgettes are tender plants. A brief frost can destroy leaves, so don't transplant simply because a sunny afternoon feels like summer. Wait until overnight conditions are reliably mild.
Harden plants off gradually by putting them outside for increasing periods during the day, bringing them under cover overnight at first. Shelter them from strong wind while they adjust.
In northern England, a later planting date may be sensible compared with an exposed garden in the south. Strong young plants in warm soil generally overtake stressed seedlings planted too early.
Prepare the planting position
Choose a sunny, sheltered spot with fertile soil that holds moisture but drains freely. Dig in well-rotted compost around the planting area several weeks beforehand or apply a suitable organic mulch in a no-dig bed.
Allow at least 90cm between ordinary plants. Courgettes develop broad leaves that can shade neighbouring vegetables, so position them where their mature spread won't overwhelm a narrow path or smaller crops.
Water the seedling before transplanting, remove the pot gently and plant it at roughly its previous depth. Firm the soil and water well. Check for slug damage during the first few nights.
Can you grow zucchini in pots?
Yes. Choose a compact variety and a container at least 45cm across, as recommended by the RHS. A larger pot helps stabilise moisture and gives the roots more room.
Use fresh, peat-free multipurpose compost and ensure the container drains well. Set one plant in the middle instead of cramming in several seedlings. Put the pot somewhere sunny and accessible, as you'll need to water and harvest frequently.
Container-grown courgettes can dry very quickly during a heatwave. A small decorative pot may look attractive in May but leave the roots stressed by July.
How often should you water zucchini?
Courgettes are thirsty during summer growth and fruit development. Water around the roots when the soil is beginning to dry, giving a thorough soak instead of a quick surface splash.
A plant in open ground may cope with less frequent watering than one in a pot. Check the soil beneath its surface and adjust according to rainfall, temperature and the size of the plant.
Avoid constantly soaking the leaves. Directing water towards the roots can reduce the time foliage remains damp, which may help limit fungal problems.
If fruits begin shrivelling or the plant wilts, inspect moisture and drainage. Waterlogging damages roots too, so adding water to already saturated compost won't solve the problem.
Feeding zucchini plants
Courgettes crop heavily and benefit from fertile soil. Where soil is depleted or a plant is growing in a container, an appropriate liquid feed may help during flowering and fruiting.
Follow the instructions on the fertiliser, particularly dilution and frequency. Too much nitrogen can encourage an enormous leafy plant with disappointing fruit production.
Where plants look pale or weak, check warmth, light and root health before assuming a nutrient deficiency. A cold, waterlogged plant cannot make good use of additional fertiliser.
Male and female flowers explained
Courgette plants normally produce separate male and female flowers. Male flowers grow on slender stalks. Female flowers have a small swelling behind the petals resembling a miniature courgette.
Insects move pollen from male flowers to female flowers. It's normal for plants to produce many male flowers before the first females appear, especially early in the season.
If a tiny fruit forms and then rots at the blossom end, incomplete pollination may be a reason. Cold or wet weather can limit insect visits. On a dry morning, you can transfer pollen from a freshly opened male flower to a female flower by hand.
When and how to harvest zucchini
Pick fruit while it is young and tender, commonly around 10–20cm long for elongated varieties, depending on the type and your preference. Smaller courgettes usually have a delicate texture and fewer large seeds.
Use clean secateurs or a knife to cut the fruit with a little stalk attached. Don't twist and pull hard, as you may damage the main plant.
Look underneath leaves every day or two in warm weather. A hidden courgette can grow into a marrow surprisingly quickly. Regular picking encourages new fruit to develop.
Courgette flowers are also used in cooking, but don't remove every flower if you want plenty of fruit. If you pick flowers, make sure you can distinguish the male and female ones.
Problems with zucchini plants
White powder on leaves: Powdery mildew commonly appears later in the season. Provide space and airflow, and remove badly affected leaves if appropriate.
Fruit stays tiny and rots: Poor pollination or growing stress may be involved. Check for female flowers and insect activity.
Seedlings disappear overnight: Slugs and snails can cause severe early damage. Inspect around young plants regularly.
No female flowers: This can happen temporarily as a plant establishes; warmer conditions may improve the balance.
Bitter fruit: Occasionally courgettes develop dangerously high levels of bitter compounds. Never eat a courgette that tastes unusually bitter; discard it, and don't attempt to cook the bitterness away.
End-of-season care
Courgettes stop growing well as temperatures fall and frost arrives. Remove exhausted plants once cropping ends. Compost healthy material, but follow disease-management guidance for severely affected plants.
Clean containers before reusing them and refresh compost for a different crop. Next year, choose a sunny spot, start seeds at the right time and grow fewer plants well.
Source
Royal Horticultural Society: How to grow courgettes and Courgette, marrow and squash problems.