What is squash?

What is squash? Squash is both an umbrella term that covers a number of crops from the Cucurbitaceae family (courgettes, marrows, gourds, pumpkins, etc.) and a specific term for some of those crops (summer squash and winter squash). It is these last two that the article focuses on although many of the comments can apply over the whole range.

20 years ago squash was a minority crop and many customers did not know what to do with it. I had one customer who wanted a box of mixed squash so we put together a mix that included Table Ace, Onion, Vegetable Spaghetti, Turk’s Turban, Acorn and Butternut. When asked she said it was for the Harvest Festival display not for eating!

Today squash are more popular due in part to the information given out by growers and also to the higher profile in cookery programmes and recipe books. Squash provide an exotic touch to boxes and market displays and when grown with the other crops in the family they can provide a useful contribution to the bottom line. They are fairly easy to grow and once established they require little in the way of detailed attention.

About Squash

Rotation and fertility needs:

Squash plants are described as heavy feeders but they are not as heavy as brassicas or potatoes. In the rotation they should generally sit somewhere in the middle of the vegetable cropping sequence i.e. after brassicas and before roots and legumes. Rotations do not follow a ‘one size fits all’ approach and they can sometimes be found at the end of the vegetable sequence having been undersown with red clover for an early start to the fertility break.

Squash are tolerant of a wide range of soils although ideally the soil should be light to medium in texture, well drained and with a good level of organic matter. The addition of compost or well composted manure can be helpful in providing a fertility boost and improved water holding capacity. Too much nitrogen relative to potassium will give plenty of vegetative growth with little in the way of fruit so beware of overdoing the fertility especially when using manures. This is generally a planted crop (see below) so a very fine tilth is not necessary when cultivating but loosening at depth will be important in fine textured soils.

Establishment/early growth:

It is possible to sow the seed direct in the ground but it is much more common for plants to be raised in pots or large blocks under cover. These plants are frost tender so should not be planted out until the danger of late frost is past. Even then there can be a risk from cold east and north winds which can scorch the leaves of new plants even when they have been fully hardened off. The use of fleece can be helpful in protecting and bringing on early crops. Irrigation can be important is establishing the crop and getting it away especially where spring is dry as for this year.

Summer squash are generally bush types so they can be planted in rows 600-900mm (24-36 inches) apart with one or two rows to the bed depending on the width of the bed. Winter squash are generally vine types and will trail vigorously across the beds often producing a continuous cover in all directions. Space the plants at least 900mm (36 inches) apart in the row and allow plenty of room between the rows. If using fairly narrow beds consider planting alternate beds and leaving the intervening beds empty (or sown with clover).

Ongoing care/maintenance:

Ongoing irrigation is not essential unless there is a prolonged drought but it can be helpful in increasing yield and ensuring steady production. It can also help to reduce the susceptibility to powdery mildew (see below). Observation of the growing crop is important for early diagnosis of problems – cold, dry years can lead to slow establishment but the plants will ‘kick in’ eventually.

Summer squash can start cropping fairly quickly so an eye will need to be kept on developing fruits so they can be harvested at their optimum size and condition. The trailing winter squash may need some attention in terms of where the vines are running – they can be a nuisance if they invade an adjacent crop.

Weed, pest and disease control:

Weed control can be important in the early stages and as ever the cleaner the bed at the start of the season the easier subsequent weed control will be. Choice of equipment will depend on the scale of the operation and prevailing conditions (and what you have on the yard). Great care should be taken around these plants as the roots can be quite shallow and the leaf stems very brittle because of their semi-succulent nature. Once the plants have developed a canopy access for weeding is virtually impossible and most weeds are shaded out.

Pest problems are relatively few. Slugs can be a problem during the establishment phase especially if the plants are slow to grow away while rodents might cause a problem as the fruit is ripening.

The main disease problem is powdery mildew (Erysiphe cichoracearum) and this initially shows as large white powdery spots on the older leaves. These can enlarge to the point where the leaf effectively loses its function and dies. Summer squash can grow quickly enough to stay ahead of the disease but winter crops can be devastated leaving only small partly developed fruit for a disappointing harvest.

Powdery mildew tends to affect older plants and is more likely to strike when the plants are under water stress so regular irrigation can reduce the impact during dry spells. Sulphur has been used to treat the problem in the past but potassium bicarbonate is more effective. This has recently been approved for inclusion in the EU organic regulations but as with all inputs check with your control body before considering its use.

Young fruit can be susceptible to botrytis (Botrytis cinerea) in wet or humid weather often developing from the soggy flower as it dies off. Be on the alert and remove any affected fruits – weeds can affect airflow between the plants and may need to be removed. There are a number of viruses such as cucumber mosaic virus that can affect the crop but these are relatively uncommon.


Most varieties are open-pollinated but the number of F1 hybrids is increasing. Organic seed availability is good but not always in the popular varieties

  • Summer Squash: patty pan or scallopini type because of the fruit shape Sunburst F1 is a good example of the yellow fruited type – green and white types also available.
  • Acorn Squash: a winter type that can be used for summer picking, does not store well. Smallish fruits often green or dark green. Table Ace F1 and Table Star.
  • Kabocha or Buttercup Squash: small to medium slightly flattened round fruit with orange flesh that sweetens during storage. Crown Prince F1.
  • Butternut Squash: popular with consumers thanks to mediaprofile. Cylindrical with a bulbed end and light tan skin. Hawk F1 and Hunter F1 good for UK but not in organic seed.
  • Sweet Dumpling Squash: Medium fruits often with green stripes on a paler background. Stores well. Delicata (cylindrical) and Sweet Dumpling (blocky).
  • Hubbard Squash: medium to large, round with neck, variety of colours. Includes the reliable bright orange Uchiki Kuri or Onion squash and Green Hokkaido.


Summer squash should be harvested regularly even if market demand is low so that new fruit continue to develop. Over-sized fruit are not popular with customers. Cold storage can be useful for removing field heat during hot spells. Winter squash tend to be harvested all in one go at the end of the season and most producers will then store them well into winter. Their skins need to be ‘cured’ to ensure that the internal flesh stays in good condition. This will need a period of warmth (25oC or more) for at least a week – a spare polytunnel can be handy if field conditions are cool. Long term storage should not be left to chance – winter squash will survive in a cool dark shed but condition may suffer. Ideal storage requires an ambient temperature of 10-15oC and around 60% relative humidity.

Marketing options:

Summer and winter squash can be incorporated into all types of direct and local marketing with good effect. The range of colours and shapes can create impact on market stalls, and can also provide a welcome contrast in a vegetable box. There will still be a need to supply cooking advice and recipes in vegetable boxes. There is a lot of focus on the Butternut types but the potential range is very wide and it will always be worth trying out new types and varieties.

Growing squash to contract is a very different experience. The usual caveats apply such as agreeing in advance the varieties to be grown, the grading criteria and the delivery/collection arrangements. It is unlikely that there are large contracts out there waiting for a keen grower to come forward but squash could be a line to add to an existing contract or programme.

What next?

Further information can be found in 2 excellent books: Growing Green by Ian Tolhurst and Jenny Hall, and Organic Vegetable Production edited by Margi Lennartsson and Gareth Davies. Commercial seed catalogues can also be a good source of basic information especially where the company specialises in squash seed e.g. Tozers. Always check www.organicxseeds.co.uk for organic seed availability and seek justified derogations where the varieties you want are not available. Consider growing a range of varieties if introducing the crop for the first time and respond to your customers’ choices.

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