How to grow courgettes and the best varieties

Courgettes are a summer favourite that produce masses of fruit so you'll only need a couple of plants for most households.

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How to grow courgettes: month by month

When to sow courgettes

Courgettes are very sensitive to frost. Sow the seeds in late April or early May, no more than four weeks before it’s safe to plant outside in your area. Sow the large seeds individually into 7cm pots of a Best Buy compost for sowing seeds in a heated propagator or on a warm windowsill at about 20ºC. For most households, two plants will produce more than enough fruit.

Best courgette varieties

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Full testing results for courgettes

Courgettes

How we test courgettes

• We grew 22 varieties of green, yellow and striped courgettes, selecting new or previously untested varieties to grow alongside previous Best Buys. 
• We sowed the seeds in modular trays in a greenhouse in mid-May, and then planted out the best three plants of each variety in open ground. 
• We waited until after the risk of frost had passed in mid-June to plant out. 
• The ripe fruit was picked twice weekly in peak season, and we recorded the number and weight of those that were more than 10cm long. We also assessed the quality and characteristics of 10 representative fruit from each variety. 
• We tasted the fruit, both raw and lightly steamed, assessing each one for the strength and attractiveness of its flavour, as well as the succulence and texture of the skin, flesh and pulp.

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Growing courgettes

Planting

Dig a hole about 30cm in depth and diameter. Fill it with a mixture of soil and garden compost or well-rotted manure, leaving a slight mound. Wait until the danger of frost has completely passed before you plant out in late May or early June. By this time, the young plants should have at least one large leaf.

Growing courgettes in pots

Some varieties are compact enough to grow in pots, such as 'Sure Thing' and 'Patio Star'. Use a container that has a volume of at least 10L and use a Best Buy compost for containers mixed with a Best Buy controlled-release fertiliser. Check if the compost feels dry to the touch every day and water thoroughly when needed. Feed plants in containers with a tomato food (high in potash) to encourage fruit.

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Growing courgettes vertically

'Climbing' varieties of courgettes have been bred to grow vertically. They have longer internodes (the length of stem between leaves) than most. Climbing varieties include 'Black Forest', 'Wave Climber' and 'Shooting Star' (yellow fruited).They're happiest sprawling up to 1.5m along the ground, but you can train them up a support by tying them in at frequent intervals. The fruits develop one per leaf joint up the stem and are very easy to pick.

Protecting from frost

Cover them with fleece until they are growing strongly.

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Watering

In dry weather, water every 2 to 3 days with a decent amount. When it's hot, each plant can produce one or even two courgettes every day, when there is plenty of moisture around the roots.

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How and when to harvest

Harvest in: July to September

Harvest the fruits when they reach 10-15cm long, or even smaller, to avoid a glut. If any fruit get missed and grow too large, cut them off to encourage the plant to produce more fruit.

Common courgette growing problems

Powdery mildew

Powdery mildew usually appears in late summer or early autumn as the plants start to run out of steam. You will first see a white dusting on the leaves, which gradually becomes more severe, before the leaves turn yellow and die. 

Read more about how to treat powdery mildew on plants.

Strange-coloured courgette leaves

White or sometimes almost silvery smooth-surfaced patches of discolouration on perfectly good, healthy and green leaves often cause unnecessary concern. Many varieties of courgette and marrow have this appearance and it is perfectly normal and nothing to worry about as it is just a varietal characteristic. Yellow-fruited varieties may also produce yellow leaves and again are nothing to worry about.

Rotting courgette fruits

The fruits start to develop normally and then, when still quite small, start to discolour and rot at the flower end. The rot then spreads back along the fruit towards the stem. This invariably starts when the petals of the fading flower start to deteriorate and the rot then spreads into the fruit. The petals rot fairly easily and very rapidly during wet weather.

To prevent it happening, always apply water direct to the base of the plants and avoid wetting the flowers, never water from overhead. In wet weather remove the flowers as soon as the fruit has started to form and that way the problem cannot start.

No fruit

Courgettes, squash and their relatives are all thirsty plants and if they are to perform well they need a fair amount of feeding, too. During dry conditions the plant conserves energy by changing the proportion of male to female flowers. If the soil is too dry they produce more male flowers and, as a result, the crop levels can be dramatically reduced. 

Good soil improvement before planting, plenty of water, and the use of a deep mulch with soil improver to conserve soil moisture during the growing season will all help to reduce the problem.

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Virus

Courgettes, squash and their relatives are prone to virus infections and symptoms include yellowing, poor growth, stunting and mosaicing, ring-spotting and streaking of the foliage, usually combined with a very poor or non-existent yield. The most commonly seen virus is cucumber mosaic. Viruses are usually spread by handling, or by sap-sucking pests, such as greenfly, as they feed.

Unfortunately, any fruits which do form on virus-affected plants tend to be small, pitted and very unpleasant to eat. If suspect plants appear, remove and dispose of them promptly, but always wash your hands thoroughly after handling virusy or suspect plants.

There are no controls available for virus infections, so avoidance is the key. Check plants regularly and control any pests found.  The following year, try to grow virus-resistant varieties, such as courgette 'Defender'.