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How to Grow Squashes RHS GYO Guide

By The RHS Advice Team

• Getting Started
• Choosing What To Grow
• Preparing The Ground
• Sowing
• Planting
• Plant Care
• Pruning And Training
• Harvesting
• Storing
• Problem Solving

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Getting Started

Squashes are eye-catching and productive plants, producing fruits in a wide choice of colours, shapes, sizes and flavours. They range from large sprawling vines to more compact ‘bush’ plants, so there are types to suit all gardens.

Squashes are closely related to pumpkins and courgettes, which are all known botanically as cucurbits – most are varieties of Cucurbita moschata, C. maxima or C. pepo. All are grown in a similar way, thriving in rich, moisture-retentive soil, with lots of warm sunshine. These tender plants are best started from seed indoors in spring, so they do need some attention initially, but once transplanted outdoors they usually grow rapidly and can be highly productive.Squashes are usually grown in the ground, as they need plenty of space, but compact varieties of summer squash can be grown in large containers.

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Choosing What To Grow

There are two main types of squash – summer and winter. The fruits of summer squashes have a thin skin (like courgettes), are picked when young and don’t store for long, while winter squashes (like butternuts) are grown to maturity then stored for use into winter. There are various categories based on fruit shape, including acorn squashes, patty pans and crooknecks, and many varieties too, producing fruits of various colours, sizes and flavours.Some varieties are vigorous trailing plants that spread for several metres or can be grown vertically up supports. There are also bush types, which stay reasonably compact, although still take up about a square metre. Smaller varieties can be grown in large containers, but most fare best in the ground. So choose varieties that suit the amount of growing space you have available. Also look for varieties with an RHS Award of Garden Merit (AGM), as these should crop reliably – see our list of AGM fruit and veg (135kB pdf) and our Recommended Varieties below. You’ll also find squashes growing in the veg areas at RHS gardens over the summer months, so do visit to compare varieties and pick up growing tips.

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Choosing squash and pumpkin varieties

What and where to buy

You’ll find a wide choice of varieties as seed in garden centres and from online retailers.Young plants are also available in spring and early summer, ready for planting out – ideal if you only want one or two, or don’t have space indoors to start them off yourself. However, the choice of varieties will be quite limited.

Recommended Varieties

‘Crown Prince’ AGM

Winter squash – trailing type. Fruits have bluish skin, orange flesh, good flavour and store well.

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'Harlequin' AGM

Winter squash – acorn type, with green, gold and yellow fruits. Stores well when fully ripe.

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‘Sunburst’ AGM

Summer squash – patty-pan variety, its small fruits have a yellow skin and nutty flavour.

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'Harrier' AGM

Winter squash – butternut type with yellow, pear-shaped fruits that have tasty orange flesh.

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'Sunbeam' AGM

Summer squash – small, yellow patty-pan type. Image © Shutterstock

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'Sweet Dumpling' AGM

Winter squash – small fruits, 10cm in diameter. Cream skin with green stripes and sweet orange flesh.

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Preparing The Ground

Choose a warm growing site in full sun, with rich, moisture-retentive but not waterlogged soil. Squashes also need plenty of space – even the more compact bush varieties can easily spread to 90cm (3ft) across.Before sowing or planting outdoors, prepare the ground where each squash plant will grow. Make a hole about 30cm (1ft) wide and deep, then fill it with a mix of soil and organic matter, such as home-made garden compost. Alternatively, if you’re practising no-dig, mulch the surface and sow or plant into the mulch. Space each sowing/planting site at least 90cm (3ft) apart for bush plants and 1.5m (5ft) for trailing plants.You can also plant summer squashes in growing bags and large containers of peat-free multi-purpose or soil-based compost.

Related RHS Guides

No-dig gardeningVegetables in containers

Sowing

Squashes are usually sown indoors in spring, for more reliable germination and to give them a head start, then planted out after the last frost. They can be sown outdoors too, but not until late May or early June. Germination outdoors may be less reliable if temperatures dip, and the seedlings are vulnerable to slugs and snails, as well as poor weather.

Sowing indoors

Indoor sowing usually gives an earlier and larger crop, as it provides a longer growing season. It’s particularly beneficial in colder regions, where outdoor sowing would have to be quite late. It keeps the tender seedlings safe from unexpected late frosts.Sow squash seeds from mid- to late April, positioning them on their side, 13mm (½in) deep, in 7.5cm (3in) pots or modular trays of peat-free multi-purpose compost. Sow only one seed per pot/module, to minimise root disturbance when transplanting later on. Keep at 18–21°C (65–70°F) in a heated propagator or on a warm windowsill. Cover with a clear lid or polythene bag to hold in moisture, until the seedlings appear. For more sowing details, see our guides below.Water the seedlings regularly and keep in good light, until ready to plant out after the last frost – see Planting, below.

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Sowing seeds indoors – step by stepUsing peat-free compost for seeds and cuttings

Sowing outdoors

Squash seeds can be sown outdoors in late May or early June. Prepare the ground as detailed above, spacing each sowing site 90cm (3ft) apart for bush varieties and 1.5m (5ft) for trailing varieties. If possible, warm the soil for a couple of weeks ahead of sowing by covering each sowing site with a cloche or plastic-free fleece.Sow two or three seeds into each prepared sowing site, 2.5cm (1in) deep, then protect them with a cloche or plastic-free fleece. Leave it in place for as long as possible after germination. If more than one seedling germinates in each growing site, thin out to leave just the strongest one.

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Sowing veg outdoorsSow outdoors – step by step

Planting

You can plant indoor-raised or bought plants outside after the last frost. But first, harden them off to gradually acclimatise them to outdoor conditions. Plant young squash plants into prepared ground (see above), taking care not to disturb the roots. Firm them in gently, then water well. Space bush varieties 90cm (3ft) apart and trailing varieties 1.5m (5ft) apart.You can also plant summer squashes in growing bags or large containers in a sunny, open spot. Plant one or two per growing bag or one in a container at least 45cm (18in) wide, filled with peat-free multi-purpose or soil-based compost. Make sure there is plenty of space around the container, to ensure good air circulation and allow plants to spread. Overcrowded conditions can encourage fungal diseases.

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Vegetables in containersVegetables: transplanting

Plant Care

Watering

Squashes are thirsty plants, especially when fruiting, so water regularly in dry spells. Insufficient water can also encourage powdery mildew. Try not to wet the leaves – water directly onto the soil. To make this easier, sink a plant pot into the ground beside each plant, then pour the water into it. This ensures the water goes down to the roots. It’s also a good idea to insert a short cane beside trailing plants, so it’s easy to tell where the centre is after it has grown lots of leaves and long shoots. Use rainwater from a butt whenever possible, and ideally water early in the morning or in the evening, to reduce evaporation. For more water-saving tips, see our guides below.

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Collecting rainwaterWatering vegetables

Mulching

After planting, cover the soil surface with a thick layer of mulch, such as home-made garden compost, to help hold in moisture and reduce the need for watering. Leave a gap around the base of the plant stem though, to keep dampness away, which could lead to rotting.

Related RHS Guides

Mulches and mulchingHow to mulchOrganic matter

Feeding

Squashes growing in the ground shouldn’t need feeding, but to get a good crop in containers or growing bags it’s best to feed regularly. Apply an organic-based, high potassium liquid fertiliser every 10 to 14 days once the first fruits start to swell.

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Looking after plants in potsChoosing and using fertiliser

Ripening winter squashes

With winter squashes, place a tile, brick or wooden board beneath larger fruits to lift them off the damp soil and prevent rotting. Also make sure they are exposed to full sun, to aid ripening.

Pruning And Training

If you have plenty of space, trailing types can be left to sprawl over the ground, but if you need to limit their spread, you can train the stems around in a large circle, inserting short canes to hold them in place. You can also simply cut off any stems that stray beyond their bounds.Trailing squashes can also be trained up supports – such as an arch, pergola, wigwam of hazel stakes or a strong trellis – but make sure they’re large and sturdy enough to carry these vigorous plants and their crop. You may need to use netting to support individual heavy fruits, so smaller-fruited varieties may be more suitable.

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Growing veg verticallyMaking veg supports

Harvesting

Summer squashes produce fruit for several months, from mid-summer onwards, sometimes right up to the first frost. Harvest their fruits when small and tasty, with a soft skin. Regular picking encourages further fruits to form.Winter squashes can also be harvested and used straight away. Alternatively, once ripened, they can be stored for many months, for use through the winter. Keep the fruits on the plant for as long as possible to develop the best flavour, but pick them before any frosts are likely. Cut the fruits from the plant with at least 10cm (4in) of stem still attached – if you cut too close to the fruit, it leaves a soft area that is vulnerable to rotting in storage.

Storing

With winter squashes for storing, let the fruits fully ripen on the plant – the riper they are when harvested, the better they’ll keep. Then lay them out in the sun for an additional week or two, either outdoors or in a greenhouse, to harden the skin, which also helps to ensure they store well. Make sure they are safely inside before the first frost.Then store the fruits in a well-ventilated place at 10–15°C (50–60°F), spaced out so they don’t touch. Depending on the variety, winter squashes should keep for three months or more. Check them regularly for any signs of deterioration or rot.

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Guide to storing winter squashes

Problem Solving

Squashes are tender plants, so are susceptible to cold and frost. They can also be affected by various diseases, and slugs and snails may eat young plants – see Common problems below for more details.

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Controlling problems without chemicalsPreventing problems

Common Problems

Courgette, marrow, pumpkin and squash problems

Courgettes, marrows, pumpkins, squashes and other members of the cucurbit family are fun to grow. It can be worrying, then, when problems strike. Know...

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Grey mould

Grey mould, caused by the fungus Botrytis cinerea, is a very common disease, causing a soft decay of plant tissues accompanied by a growth of fuzzy gr...

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Slugs and snails

Slugs and snails are common garden animals, and they are well suited to the damp, mild climate of the UK. A few species feed on garden plants, but mos...

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