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Courgette/Zucchini, including Summer Squash

Cucurbita pepo subs. pepo – the name for all summer squash

This lesson has a lot of information about summer squash, using courgettes as the main example.

27th July – one plant of Twinkle F1 summer squash has been left unpicked for three weeks

Summer squash are a subspecies of the pepo species, a large group of plants that grow with the same timings and in similar ways. Examples are Pattypan, Tromboncino, Crookneck and Straightneck. Sow these at the same time and use the same methods and spacings as I give here for courgettes or ‘zucchini’, which are also summer squash.

  • Compared to varieties for winter, summer squash are eaten at an immature stage with soft skin.
  • They grow fast and crop copiously.
  • If summer squash are allowed to mature on the plant, their skin becomes hard.
  • Even with a hard skin, summer squash do not store nearly as long as winter squash, and their flesh is less sweet.
  • Most summer squash, including courgettes, make bushy plants, rather than the trailing plants of winter squash which are a different Cucurbita species – see Lesson 27  in Course 3B.
Striata – a long, thin courgette variety
An early summer courgette flower on 3rd June, when plants are free from mildew disease
4th June – mixed varieties of courgette plants and a winter squash plant on the far left; this gives an idea of spacing

The harvest time and method is to cut small fruits when they are tender. They are babies and immature, with no seeds inside. If you allow them to grow more, then seeds develop, flavours change and courgettes, for example, transform into marrows.

You can harvest most summer squash fruits at the stage about halfway between baby and hard-skinned. The flavour becomes less sweet but richer in other ways. I suggest you have fun trying harvests of different sized fruits, to find out how you like them most.

There is no special soil preparation, except perhaps a little more compost than for other vegetables. At Homeacres I add nothing extra to the squash beds, compared to, say, a bed for carrots. Nonetheless, fast growth and greedy roots mean these plants like nothing better than growing on a compost heap or pile of manure.

Late April – planting an early courgette plant in a half-mature compost heap
18th July – the same plant on the heap of ripening compost was not quite as early as I had hoped
August – early Gem F1 courgettes that have grown into marrows, on top of a heap of 18-month-old cow manure

Important note on courgettes

If your courgettes ever taste noticeably bitter, they may contain toxic cucurbitacins. Poisonous courgettes were reported in a few UK gardens in 2020, apparently from bad seed stock which had been sold by as many as three different seed companies.  The variety was Zucchini F1, best avoided.

  • Plants grow abnormally with more leaf than fruit – this would be one sign to alert you.
  • Such a poison is exceptionally rare and I absolutely do not want you to be discouraged from growing these amazing vegetables. Just watch out for those signs of imbalanced growth, and for fruits that taste so bitter that they are disgusting.
  • If a courgette plant’s growth habit is normal, as you see in the photos here, then there is nothing to worry about.

Harvest period

  • Days from seed to first harvest: 50–75

  • Best climate is warm, not too dry, can be hot.
  • They are annuals, killed by frost.
An extreme solution for frost protection on this plant
These courgettes were fleeced when planted in May on a morning with a light frost; now, by 13th June, they’re still protected because it’s a cool wet summer

Why grow them

An important bonus of homegrown, as opposed to bought courgettes, is that you can choose the size of fruit you like. If, for example, you enjoy them really small, then you can pick them really small!

Plants grow at a rapid rate, such that, from just one, you can expect a regular and large supply of tasty fruit. The flavour and texture are best when they are fresh, so this is a huge advantage for homegrown.

There is also something iconic about the first bright yellow courgette flowers in late spring. They are almost tropical, suddenly there in your garden. They are one of my favourite sights of the season, a sign that summer has arrived.

  • The flowers are delicious to eat, for example when fried after being dipped in a little batter.
  • You can eat the male flowers as well.

Save space?

Plants quickly grow large, and in small gardens they may not be practical because of how much space they require. There is an option with one or two varieties to grow them up strings. The one I grew is Black Forest F1.

I tried this, and it worked for a while with some decent first harvests. However, I then found that the large, heavy leaves, when blowing in the wind, caused too much movement of the stem against the string and damaged it.

Even if you tie the stem to a stake, you have to be careful that the string does not rub into the stem. Stems are broader and more tender than their close relative, the cucumber.

  • Plants in a container, like the one below, need much water – at least every day in summer.
Late July – this Black Forest F1 courgette is thriving; it has string buried under the rootball
Mid-August – the same climbing courgette seventeen days later
Five days later, just before the stem broke – next time I would deleaf fifty per cent of the lower leaves

Suitable for containers/shade?

I would say not to grow in a container, because of how they grow so large. Or perhaps you can succeed with the vertical training, in which case regular removal of lower leaves makes it easier to support plants.

If you have something large, like an old bath, that would be an option, as long as you water frequently and copiously in hot weather.

Some varieties are called ‘compact’, such as Goldrush F1, but it’s a relative term.

  • Courgette plants can grow in shade, they will just grow more slowly.


Have a browse of any catalogue or website for the immense range of harvest possibilities. Fruits can be long or round, green or yellow, and in many shades, with compact leaves at their centre or open habits. The latter are easier for finding fruits to pick.

  • Cocozelle grows long, thin and slightly striped courgettes on trailing plants. It’s sometimes called an ‘heirloom’ variety, which means that it has been around for a while. The term is not a mark of quality.
  • Defender and Tuscany F1 fruits are dark green, smooth and chunky on compact plants.
  • Early Gem F1 is prolific with light green fruits: I have grown this since 1983. The leaves are pretty with silver streaks.
  • Atena Polka and Soleil F1 are productive for yellow fruiting varieties. Note that they have a yellow colour in their leaves – it’s not a disease.
  • Eight Ball F1 grows round fruits, which you harvest at any size, from golf to tennis ball.
  • Custard White is a traditional pattypan bush plant with white, scalloped fruits. Sunburst and Twinkle F1 grow a mass of yellow pattypans – see the photo above.
sow & propagate
Transplant - Size, time of year, Spacing, support
container growing
Prune and train plants/thin fruit
Harvest times and method
Potential problems


Towards the end of summer, you will probably find that it is less appealing to eat courgettes and squash every day than it was in early summer! They have a justified reputation for overwhelming us with their abundance.

Despite this, I used to be attached to my plants until they were killed by frost. I had the feeling that they represented summer lingering, ahead of colder and darker days.

  • Frost does at least make clearing easy, because it converts a large plant into a few fibres – it’s quite a remarkable transformation.

Over succeeding years I have come to appreciate that there are more interesting possibilities for plantings in early autumn, after removing courgette plants at the end of summer. The choice is yours, and it is a nice option to have.

I suggest using a long-handled sharp spade to cut through the main stem at ground level, leaving all roots in the ground. Carry the plant to your compost heap and squash it down, always being careful not to let the spines rub your skin. Now simply rake the ground level – probably also necessary to water it thoroughly – and set out your new transplants.

By 30th August, these courgettes are now ready to clear. They are still cropping but are overpowering other nearby vegetables, and we have plenty of other harvests
Six days later, the courgette plants have been cleared from the bed to the right, which is now planted with small endive and mustard transplants

Follow with

There are several vegetables that can be transplanted through early autumn (much better than sowing direct), such as endives, salad rocket and Oriental leaves. By mid-autumn, the best options change, to transplants for overwintering as small plants. Examples are salad onions, lettuce and spring cabbage.