Squash

Squashes come in a huge range of shapes and sizes, from massive pumpkins to tiny patty pans. There are winter squashes, such as pumpkins and butternuts, which can be stored, and summer squashes, which are harvested when immature and don’t store well. They are all relatively easy to grow from seed.

Jobs to do now

  • Water
  • Harvest

Month by month

Sow

Sow

Squashes are usually sown indoors in pots, to get them off to an early start, then planted out after the last frost. This will usually give you an earlier and larger crop, and is particularly useful in colder regions. It also keeps the vulnerable seedlings safe from slugs and snails.

From mid- to late April, sow the flat seeds on their side, 13mm (½in) deep, in 7.5cm (3in) pots of compost and keep at 18-21ºC (65-70ºF).

Seeds can also be sown outdoors in the spot where they are to grow in late May or early June.

Sow two or three seeds at each sowing site, 2.5cm (1in) deep, then cover with cloches, jars or plastic. Leave in place for two weeks, or as long as possible, after germination. Thin the seedlings to leave the strongest one. If you want more than one plant, space your sowing sites about 90cm (3ft) apart.

If you don’t have the space indoors to raise squashes from seed, you can buy young plants from garden centres in spring and these can usually be planted outdoors straight away. Check plant labels for details.

Grow

Grow

Before planting or sowing seeds outdoors, prepare the ground where each squash will grow. 

Make a hole about a spade’s depth, width and height and fill with a mixture of home-made compost or well-rotted manure and soil. Sprinkle a general purpose fertiliser, such as Vitax Q4, over the soil at a rate of two handfuls per square metre/yard. Plant one squash or make one sowing in the middle.

If growing more than one squash, space bush plants 90cm (3ft) apart and trailing plants 1.5m (5ft).

You can also plant summer squashes in growing bags or containers at least 45cm (18in) wide. Plant one or two per growing bag, or one per container.

Indoor-raised plants can be planted outside after the last frost in your area, but first you must harden them off to acclimatise them to outdoor conditions. Do this by moving them into a coldframe for a week or, if you don’t have a coldframe, move them outdoors during the day, then bring in at night for a week. The following week, leave them out in a sheltered spot all day and night.

Keep the soil or compost constantly moist by watering around the plants, not over them. As they need plenty of water, sink a 15cm (6in) pot alongside each plant, then water into it. This ensures the water goes down to the roots and doesn’t sit around the neck of the plant, which can lead to rotting.

Feed every 10-14 days with a high potassium liquid fertiliser, such as tomato feed, once the first fruits start to swell.

Pumpkin fruits should be supported off the soil on a piece of tile or glass.

Common problems

Powdery Mildew
Powdery Mildew

Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.

Remedy

Keep the soil moist and grow in cooler locations.

No fruit, or fruit rotting when very small

This is a physiological problem, caused by the growing conditions, not a pest or disease. It is a problem when the weather in early summer is cool and this causes inadequate pollination.

Remedy

This is usually a temporary problem and once the weather starts to improve, so will pollination. You can try to hand-pollinate plants yourself by removing a male flower (no swelling at their base) and brushing the central parts against the centre of a female flower (female flowers have a swelling at the base – this is the beginning of the fruit). But this is a bit of a hassle, and normally the plant will correct this problem itself.

Grey mould
Grey mould

A usually grey, fuzzy fungal growth which can begin as pale or discoloured patches. Grey mould ( botrytis) is a common disease especially in damp or humid conditions. Spores enter plants via damaged tissue, wounds or open flowers. Mould can also damage ripening fruit such as strawberries. Black resting spores survive over winter.

Remedy

Remove damaged plant parts before they can become infected. Cut out infected areas into healthy tissue and clear up infected debris. In greenhouses, reduce humidity by ventilating and avoid overcrowding of young plants and seedlings.

Harvesting

Summer squash 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 will encourage further fruits to form.

With winter squashes for storing, let the fruit mature on the plant and remove before the first frost. Ripen the skin until hard, by placing fruits in the sun for a week, either outdoors or in a greenhouse. This helps to ensure they keep well.

Store the fruits in a well-ventilated place indoors at 10–15°C (50–60°F).

Depending on the variety, winter squash should keep for three months or more.

Recipes

Masterchef’s Gregg Wallace uses a pumpkin as a bowl for a delicious squash fondue – great for parties.

Recommended Varieties

Squashes — summer

Squashes — winter

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.