Squash (Curcurbita sp.)
Of all the vegetable varieties, squashes are by far the most diverse in shape, size, and overall appearance. The sheer complexity of this vegetable group invites growers on a life-long adventure. There are many hundreds of different named varieties of squash (perhaps more types in cultivation than any other group of vegetable), each with its own fascinating history and facts about squash, but there are countless more yet to be developed, as the plants are so easy to breed and prone to cross-pollination.
Part of the trouble with dealing with these diverse vegetables is that traditional gardening books have dealt with them exclusively in terms of the ways they are used. “Summer squash” refers to those varieties that are harvested during the summer, before they are fully mature, while they are still tender, moist, and full of flavour. This group includes zucchinis, crooknecks, straightnecks, the scalloped types (pattypans), and the tender spherical squashes. “Winter squashes” are much more diverse, and include all varieties that are harvested at the end of summer when they are fully mature: Acorn, buttercup, butternut, delicata, spaghetti, all gourds, and a host of pumpkins.
This approach does a bit of a disservice to the different kinds of squashes because among pumpkins alone, there may be three different species. We think of all other types of vegetables in terms of species or subspecies and there are a couple of good reasons to shift the way we think of squashes in this direction. Most obviously, to celebrate the diverse shapes, flavours, and characteristics shown by those within a single species. Just think of Cucurbita pepo, which includes pumpkins, acorns, zucchinis, vegetable marrows, delicatas, buttercups, and many others! The second reason why this shift in approach is important is about saving seeds from year to year. All members of C. pepo can cross pollinate with one another. Likewise, all types of C. moschata can cross-pollinate among themselves – the same is true for C. maxima. You might not think that growing a zucchini next to a pumpkin could produce seeds that, if grown out, will be unpredictable to the point of uselessness, but such is the nature of the genus Cucurbita.
All forms of squash (and there are many that, for one reason or another, are not commonly grown in our area), arose in the Americas, primarily in the areas that are now Mexico and Central America. C. maxima have been in cultivation for more than 4,000 years. This great expanse of time, coupled with the plant’s luxurious tendency to cross pollinate and take on new forms, allowed indigenous Americans to cultivate or create as they traveled a spectrum of forms prior to European contact in 1492. Indeed, the English word, squash, is descended from the Narragansett word askutasquash. This was a dialect of the Massachusett speaking people, whose language is now included in the greater family of Algonquin.
Of course, it was not until Columbus’s time and onward that Europeans or Asians had any exposure to squash – as well as tomatoes, beans, and peppers. Something about squash captivated the minds of Europeans, particularly in the south, where the plants grew so well in the temperate Mediterranean region.
In 1768, the French botanist A.N. Duchesne began to examine the genus Cucurbita by painstakingly crossing male and female flowers by hand, growing out the fruit, and then growing out the resulting seeds. He made hundreds of detailed watercolour paintings of the parent and offspring fruits, and all the various cultivars he discovered. Duchesne’s remarkably dedicated work resulted in a very clear understanding of which squashes comprised which genus and parent group. Simply put, the varieties most often grown as food crops since his time look like this:
Cucurbita maxima includes the largest pumpkins, banana squashes, the buttercups, Hubbards, turban-shaped kinds, zapallitos, and some others.
Cucurbita moschata is comprised of the neck group (with very long bodies and a bulbous seed cavity at the blossom end), cheese pumpkins, tropical pumpkins, and Japonica types.
Cucurbita pepo is the most diverse group of plants in terms of its fruits. This species can produce pumpkins (smooth-skinned or warty, the oil-producing types, summer pumpkins, and many of the pumpkins grown for Jack-o’-lanterns); acorn squashes (including true, top-shaped acorns, delicatas, and Jack Be Little pumpkins); scalloped squashes; crookneck and straightneck squashes; vegetable marrow (including spaghetti squashes); zucchinis (which are always an even thickness along their length); cocozelle types (these look like zucchinis, but have a bulbous blossom end); and an amazing range of decorative gourds with a wild range of colours, shapes, and sizes. The species name pepo refers to the nature of the fruit (technically it is a berry) – thick-skinned, fleshy, and housing seeds in a small cavity at one end or along its length.
Because of their diversity, few generalizations can be made about the nutritional values of the various squashes. Summer squash (zucchinis, cocozelles, summer pumpkins, scalloped types, vegetable marrows and a handful of others) are eaten while they are immature, and are at the peak of their texture and flavour only a few days after pollination. These contain as much as 95% water, but are high in dietary fibre, protein, vitamin C, and potassium. Because winter squashes are left to mature, they contain significantly greater quantities of sugar, vitamins, and a much broader range of minerals. Pumpkin seeds are loaded with protein, zinc, vitamins, and are thought to lower cholesterol. Oil extracted from pumpkin seeds (which is very popular in Central and Eastern Europe) is rich with the fatty acids that maintain good blood vessel and nervous system health.
It is no surprise that squash festivals are common across North America. The fruits can be colourful, of a peculiar shape, or just enormous, so they have become symbols of the rural autumn fair. Morton, Illinois, is the self-proclaimed Pumpkin Capital of the World, and is home to the Libby’s pumpkin canning plant. In the second week of September, Morton hosts its Annual Pumpkin Festival, with all the themes we have come to expect – pumpkin cookoffs, carving, live music, lots of food, and so on. It’s also the venue for the annual “Punkin Chuckin’ Contest,” wherein competitors are invited to bring contraptions with which to hurl 5-10lb pumpkins into an open field. This competition has seen catapults, trebuchets, and all manner of pumpkin propelling devices. The Q-36 Pumpkin Modulator, however, holds the world record for pumpkin propulsion. The Q-36 is a 30m (100’) air cannon that weighs 16,000kg (36,000 lbs), and was unveiled at the Morton contest. It fired one pumpkin 1,430m (4,680’)!
How to Grow:
Difficulty: All squash are easy to grow if you can provide enough space in full sun. All squashes have very large root systems, so none are particularly suited to container growing. Allow 10-20 square feet per plant.
Timing: Direct sow or transplant in late May or early June when soil is warm.
Sowing: Build up a small hill of soil, and sow 3 to 5 seeds per hill, 2cm (1”) deep. Thin to the best looking plant by cutting, not pulling, so as not to disturb the roots.
Spacing: Summer Squash: Rows 1—2.4m (3—4′) apart with plants spaced 45—60cm (18—24”) apart. Even the bush summer squash are big plants and most gardens do not need more than 2 or 3. You need to leave room so you can get to the plants to harvest them regularly. Winter Squash: Rows 1.2—1.8m (4—6′); space plants 45—60cm (18—24”). Farm: 100′ Row: 14—28g. Acre: 1—2kg (2—4lb). Rows: 1.8—2.4m (6—8′) apart; space plants 90cm (36”) apart. Winter squash are even bigger plants and many are vines. They can be set at the edge of the garden, so that the vines go across the lawn or path.
Soil: These big plants need lots of food! Use one cup of complete organic fertilizer under each plant. Do not water until after the plants are established. Like other flowering or fruiting plants, these require full sun. Add ample organic matter to the planting site to retain moisture, and aim for a pH range of 6.0 to 6.5.
Growing: All squash grow male flowers first then the female flowers are produced. The female flowers have tiny fruits at the base of the petals and require pollination by bees mostly. Incomplete pollination often happens at the beginning of the season, and results in misshapen fruit at the flower end. Just discard these damaged fruit. You can encourage bees to your garden by planting Buckwheat and/or Phacelia. For the largest pumpkins, grow only one fruit per plant by removing all female flowers once you can verify that a fruit is forming. Gradually adjust the fruit so that is growing perpendicular to the vine. Feed the plants every two weeks with a fish-based liquid fertilizer.
Harvest: Summer squash become blander as they mature, so aim to harvest very young fruits as frequently as every day. Winter squash is ripe if your thumbnail doesn’t mark the skin and the stem is dry and brown. Cut the stem about 4cm (2”) from the fruit. Squash survive a light frost, but store better if harvested before frost.
Storage: Field-cure for 10 days in the sun, or cure indoors in a warm room for 4 or 5 days. To prevent mould sponge the skins with a solution of 10 parts water to 1 part chlorine bleach. Store at 10-15°C (50-60°F) with low humidity with good air circulation. Try on a shelf in the garage.
Seed info: In optimum conditions at least 80% of seeds will germinate. Optimum soil temperature for germination: 25°-35°C (68-95°F). Usual seed life: 2 years.
Growing for seed: All squash varieties will cross-pollinate within their species, but not between species. You can grow one variety of each of the three species side by side without any cross-pollination occurring. Isolate individual varieties within a species by 1km (½ mile) if you are planning to save the seeds for the purposes of planting again. Otherwise, plants can be hand pollinated, with the fertilized female flowers taped shut so they cannot receive any insect visitors.
Pests & Disease: Bacterial wilt (Erwinia tracheiphila) – Remove and destroy infested plants. If striped or spotted cucumber beetles appear control as soon as possible. Powdery mildew – avoid wetting foliage if possible. Water early in the day so that above ground parts will dry as quickly as possible. Avoid crowding plants and eliminate weeds around plants and garden area to improve air circulation. Viral disease – Remove and destroy entire infested plant along with immediately surrounding soil and soil clinging to roots. Eliminate wild cucumber and milkweed nearby. Control aphids early in the season by washing off with water as needed early in the day. A hard stream of water can be used to remove many aphids.
All squash plants bear their male (pollen producing) flowers at the ends of long, narrow stems like the ones shown above.
All squashes also bear female (pollen receiving) flowers. Note the thickened base of each – this is the ovary of the flower. If it is fully fertilized, it will swell into a mature, seed-bearing fruit. If you notice squash (particularly zucchini) fruit that wilt or yellow at the blossom end, it is a result of incomplete pollination. These should be cut from the plant and discarded or composted.