Unwins Seeds

How to Grow Squashes, Courgettes, Marrows & Pumpkins - Cucurbits!

Squashes, courgettes, marrows and pumpkins all come under the same fruiting vegetable family- the curcubits. All these crops have certain characteristics in common, and it pays to know these, to grow them successfully. They’re fun to grow, especially with children and easy to sow on account of their large seeds.

Outdoor cucurbits


Germination time: 5 days-1 week

These cucurbits have large seeds that you need to soak overnight before sowing. For an earlier harvest in July, sow indoors in pots and transplant outdoors in June. For a regular harvest from July to October, sow outdoors in May and June.

Indoors, sow one seed on its side in seed compost in a 9cm pot. Once germinated and having produce two or three true leaves, harden off by placing the pots of young plant outdoors by day and bringing them in at night.

Outdoors, prepare the soil and sow 3 seeds together 3cm deep at stations a meter apart – these plants spread!


As the seedlings start to develop, remove the weaker two, to leave the most robust. The seed leaves and succulent stems of young plants may prove quite a delicacy to slugs and snails so you may consider putting down slug pellets, or using organic measures.

For trailing cucurbits pinch out the tips of the main stems when they reach 60cm (2ft). This promotes side shoots and flowering.

Keep the area well watered, but keep water physically off the leaves and add a mulch of bulky manure around the plants once they have started to flower. At this point you may want to add tomato feed to promote the development of flowers and then fruit.

Cucurbits have males and female flowers. You can fertilise the female flowers by hand- just remove the male flowers (these are the ones with no fruitlets forming directly behind the petals), push back the petals and brush onto the female flowers (the ones with fruitlets behind the flower).

For pumpkins, grow fewer but larger superiors fruits by limiting tto two swelling fruits per plant. With other cucurbits you can leave a greater number of the fruiting vegetables to swell.


Keep on top of harvests daily for courgettes – otherwise they develop into less intensely flavoured marrows.

For cucurbits, harvest little and often. This promotes a longer cropping season. Use a knife to harvest as opposed to snapping off fruiting vegetables by hand. This produces a clean cut that is less likely to let in pernicious diseases, and prevents rashes- courgettes and marrow are quite rough and may cause skin reactions.

Indoor cucurbits (cucumbers and melons)

Yes, you can grow both these crops outdoors with varieties bred to be hardy in UK conditions. But if you want earlier harvests, you’ll need to grow sweet melons and fresh cucumbers under glass.

The glasshouse varieties require a bit more TLC than their outdoor-growing counterparts, but melons and cucumbers are both indoor vines and they are things of beauty, producing earlier harvests.

Before planting

Be sure to have the required level of humidity in the glasshouse. You can achieve this by water the ground early in the morning on a hot day. The vapour will increase the humidity and provide ambient moisture to the stems and roots.

You’ll also need to feed greenhouse vine crops. You can start by adding lots of organic matter or bulky compost to the soil before planting with a helping of general purpose fertiliser. The soil needs to be rich and fertile, deep and well drained. The adding of organic matter sates all these requirements.

Before planting, water the soil well to keep it moist, and warm the soil by covering with a polythene sheet for one to two weeks.

Young plants

Both cucumbers and melons have male and female flowers. The male and female flower is distinguishable in both fruits by the presence or absence of a small fruitlet at the back of the flower. It’s the female flowers that produce the fruits we want.

Once the plants have grown to the flowering stage, provide them with a balanced liquid fertiliser to ensure good healthy stem growth as well as good flower formation.

Both fruits require pinching off the tips of stems, once the plants have produced a set amount of leaves or the plant has attained a certain height – five leaves for melons and once the plant has reached the greenhouse roof for cucumbers.

The purpose of this is to encourage side shoots that produce flowering and therefore fruiting stems.

While the plants are growing make sure they have adequate ventilation on hot days, but don’t get too cold on cooler days by closing doors, windows or vents.


When you notice cucumbers and melons start to swell, apply a tomato-feed every two weeks. With melons you may need to apply little ‘hammocks’ to hold the swelling fruits, which otherwise get too big for stems to hold them without support. Cucumbers, which are not so large, don’t require this support.

At the harvesting stage, do not remove fruits from the stems simply by tearing them off. This may damage the stems and create tears that introduce pests and diseases. Cutting the fruits away from the stems with a knife or scissors is a far better practice to keep plants healthy, robust and disease free.

Pests and diseases of cucurbits

Cucumber mosaic virus

Root rot

Powdery mildew

Red spider mite



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