How to Grow Courgettes: A Practical Guide from Seed to Harvest

Courgettes are one of the most rewarding vegetables you can grow. A couple of healthy plants can produce an amazing number of courgettes through summer, and they're perfectly happy growing in the ground, raised beds or large containers.

They're also easy to grow from seed. The seeds are large and the seedlings grow quickly, and once the plants get going, they really get going.

The main thing to remember is that courgettes are hungry and thirsty plants. Give them good soil, plenty of sunshine and regular water and they'll usually reward you with more courgettes than you know what to do with.

You don't need many plants either. For most households, two or three productive plants will provide plenty. Keep picking the fruits while they're young and tender and the plants will carry on producing for weeks. You will find green, yellow and interesting shaped varieties.

When to Sow

Courgettes grow quickly, so there's really no need to sow them very early.

For most gardeners, April is a good time to start seeds indoors, although if you are later you will still get a great harvest. If you have a greenhouse or somewhere warm and bright, you can sow towards the beginning of the month. Otherwise, late April into early May is perfectly fine.

I wouldn't be tempted to start too early unless you have somewhere suitable to keep the plants. Courgette seedlings soon become enormous, and you'll quickly find yourself moving large pots from windowsill to windowsill while waiting for the weather outside to catch up.

You can also sow directly outside in late May or early June once the soil is warm and the danger of frost has passed, although starting them in pots usually gives you a useful head start.

If you want to extend the harvest, make another small sowing in late May or June. A younger plant can sometimes take over just as the first plants begin looking tired later in summer.

Sowing and Growing Seedlings

Courgettes are wonderfully straightforward to sow because the seeds are large and easy to handle.

Fill a small pot with multipurpose or seed compost and sow one seed per pot about 2cm deep. You may see advice to sow the seed on its edge, which can help prevent water sitting on top of it, although I've found courgettes generally germinate perfectly well as long as the compost isn't kept soaking wet.

Water gently and put the pots somewhere warm. Courgette seeds germinate quickly in good conditions and you'll often see the large seedlings pushing through within a week or so.

Once they've germinated, give them plenty of light. They grow rapidly and can become stretched and floppy if they're kept on a windowsill indoors.

Keep the compost moist but not waterlogged.

As the seedlings grow, move them into larger pots if their roots begin filling the originals. Don't leave them cramped for too long because courgettes are vigorous plants and soon use up the available space.

Before planting outside, harden them off gradually for a week or two. A courgette raised in a warm greenhouse won't appreciate being suddenly introduced to a cold May night.

Planting Out and Spacing

It's important to wait until the danger of frost has passed before planting courgettes outside. They're tender plants and even a light frost can finish off a young plant surprisingly quickly. Without hardening off, the growth can become stunted.

Choose a sunny, sheltered position with fertile soil. Courgettes are greedy plants, so this is one crop where adding plenty of well-rotted compost or manure before planting really is worthwhile.

Give them room. I have been tempted to plant the small courgette seedlings too close, only to regret it as they grow quickly. Allow roughly 90cm between plants for most varieties, although compact varieties can be grown closer.

Water each plant thoroughly after planting.

Courgettes also grow very well in containers, but use a large one — ideally around 40–50cm across for each plant. Small pots dry out too quickly and simply don't provide enough compost for a hungry mature plant.

If space is limited, look for compact varieties bred specifically for containers.

And don't plant six simply because six seeds germinated. Two or three healthy plants can produce an awful lot of courgettes.

Growing On

Once established, courgettes grow rapidly. Most varieties form large plants with broad leaves that quickly shade the soil underneath.

Keep the area around young plants weed-free until their leaves begin filling the space. After that, weeds usually have a much harder time competing.

Courgette leaves can look slightly alarming. They're often naturally marked with silvery patches, which can easily be mistaken for disease. If the markings follow the pattern of the leaf and the plant is growing strongly, there's usually nothing to worry about.

Older leaves can become damaged, tatty or develop mildew later in the season. I remove badly affected lower leaves, cutting them cleanly near the base. This also improves airflow and makes finding the courgettes considerably easier.

Try not to remove lots of healthy leaves unnecessarily. The plant needs them to feed the developing fruits.

Most importantly, check beneath the foliage regularly. Courgettes are remarkably good at hiding, and the perfectly sized one you miss today can look suspiciously like a marrow by the weekend.

Watering and Feeding

Courgettes need plenty of water once they're growing strongly, particularly when they're flowering and producing fruit.

Water thoroughly during dry weather rather than giving the plants a light sprinkle. Aim the water at the soil around the base rather than continually soaking the foliage. Those enormous leaves can act like umbrellas, so make sure the water is actually reaching the roots.

Container-grown courgettes need particularly close attention. A large plant on a hot summer day can use water remarkably quickly, and pots may need checking every day.

A mulch of compost or other organic matter around plants can help the soil hold moisture and reduce how often you need to water.

Once flowering and fruiting are underway, I give courgettes a high-potash liquid feed, such as tomato feed, every week or two according to the product instructions. Plants growing in containers particularly benefit because the nutrients available in the compost are limited.

Harvesting

Harvest courgettes regularly and they'll keep producing.

I like to pick them while they're still relatively small, usually around 10–15cm long. At that size they're tender, have a lovely texture and you don't have to deal with a centre full of large seeds.

Use a sharp knife or secateurs to cut the fruit from the plant, leaving a short stalk attached. The stems can be surprisingly tough, so twisting and pulling isn't worth risking damage to the plant.

During warm weather, check plants every couple of days. Courgettes can grow astonishingly quickly and it's very easy to overlook one underneath the leaves.

Regular picking also encourages the plant to continue producing more flowers and fruit.

If one does escape your attention and turns into a marrow, it isn't the end of the world. It's still usable, although the skin will be tougher and the seeds larger.

And if you find yourself leaving bags of courgettes on neighbours' doorsteps by August, congratulations — you've grown courgettes properly.

Common Problems

Courgettes are generally straightforward, but there are a few problems you're likely to encounter.

Powdery Mildew

Powdery mildew is probably the most familiar. It appears as a white, powdery coating on the leaves and becomes particularly common later in summer. Good spacing and airflow help, as does keeping plants consistently watered. A little mildew on an older plant isn't necessarily a disaster — courgettes can continue producing despite looking rather tired towards the end of the season.

Don't confuse mildew with the natural silver markings found on the leaves of many courgette varieties.

Small Fruits Turning Yellow

Small fruits turning yellow and rotting from the end are often the result of poor pollination. Courgettes produce separate male and female flowers, and insects normally move pollen between them. Cool, wet weather can reduce insect activity and you may lose a few young fruits. Once conditions improve, the problem often sorts itself out.

You can hand-pollinate if necessary by transferring pollen from a male flower to the centre of a female flower. Female flowers are easy to recognise because they already have a tiny courgette behind them.

Slugs and Snails

Slugs and snails can damage young plants, particularly just after planting out. Once courgettes become large and vigorous, they're generally much better able to cope with a little damage.

Yellowing Leaves

Yellowing leaves can be caused by several things, including old age, hungry plants, waterlogged soil or plants drying out repeatedly. Look at the whole plant rather than worrying about one old leaf near the base.

Finally, don't panic if your first flowers appear and then fall off without producing courgettes. They're often male flowers. Female flowers usually follow, and that's when the real harvest begins.