The Year of the Squash

Everything You Didn’t Want to Know About Squash – and now find Fascinating!

Squash, the native North American vegetable, was cultivated by the Cochise peoples in New Mexico where unearthed remains dated back to 4000 B.C. Squash and corn are two of the oldest sources of food grown in North America.

Today, squash is easy to grow from seed and can be successfully grown by beginning gardeners. It is one of the most diverse vegetable classes with more than twenty squash sizes or shapes, ranging in color from blue gray, orange and pink to golden yellow, pastel green, cream and forest green. Squash is receiving acclaim for its nutritional value, containing both vitamins and essential minerals.

‘Papaya Pear’ Squash

Squash was one of the first crops grown in the prehistory of the New World. Our earliest physical evidence comes from the Ocampo caves in Tamaulipas, Mexico, where several species of squash have been found along with the remains of gourds, jack beans, and other crops. These remains date to about 7000-5000 B.C.

The National Garden Bureau found the earliest use of squash was by the Cochise Indians in what is now the southwestern United States. Remains of domesticated squash dating to about 4000 B.C. were found at Bat Cave, New Mexico, along with the remains of pod corn, a primitive ancestor of what we know today as corn. This is strong evidence that squash predates corn as a domesticated crop.

For centuries after the introduction of agriculture into North America, farming was practiced primarily by Indian tribes of the Southwest, and the base of their agriculture was corn and squash. About 300-500 A.D. beans were introduced into the technology, and the farming of corn, bean and squash, by a tribe called the Anasazi, marked the beginning of a new era of prosperity. Squash is not only one of the oldest of the New World crops, it became almost universally grown.

In 1276 a major drought began in the Southwest that would last until 1299. The drought caused a migration of the southwestern tribes to the south and southeast. With the migration went the knowledge of their farming technology. By the time the Europeans arrived in 1492, variations of the corn/bean/squash technology were seen wherever corn was grown. The early settlers survived because they gained this knowledge from the Indians.

Research conducted by the National Garden Bureau found the reason why these three crops were so often grown in one plot. As the corn, bean and squash technology evolved among the Indians, they came to practice a very effective polycultural technique. The corn stalk provided a pole for the beans, and the squash was grown as a ground cover. The squash provided food, but also helped control weeds, provided kindling for cooking, and produced a good organic mulch.

The knowledge of squash seems to have entered the written records of Europe late in the 16th century. We can surmise that many settlers recorded their knowledge of this and other New World plants in their private diaries and letters home. But for the formal introduction of the plants we can look to one Thomas Hariot, a mathematician, who accompanied an expedition financed by Sir Walter Raleigh. Mr. Hariot returned to England with samples of squash and knowledge of its use learned from the Indians. In 1588, Hariot published a report that was described as the first book in English devoted to the flora and fauna of what is now the United States. Cucurbita pepo was included in the 1633 edition of Gerard’s Herbal.

The 21st century home gardener would easily recognize today’s squash from this vivid Elizabethan description. “The great long Pompion which bringeth forth thicke and rough prickly stalkes, which with their clasping tendrils take hold upon such things as are neere unto them…the floures be very great like unto a bell cup, of a yellow colour like gold, having five corners standing out like teeth…the fruite is great, thick, round, set with tick ribbes, like edges sticking forth.”

Squash is a member of the family Cucurbitacea, which includes some 90 genera and 700 species of plants. They are described as tendril climbing herbs from the tropic and temperate zones, grown for the edible fruits and for ornament. In addition to squash and pumpkins, the cucurbit family includes such familiar plants as cucumbers, melons and gourds, as well as hundreds of lesser-known herbs. Three species, C.maxima, C.moschata, and C.pepo, all contain varieties listed as squash. Squashes are commonly designated as “summer” or “winter” while most of the summer squash are from C.pepo, the winter squash occur in all three species.

Summer squash is grown and harvested during the summer. The squash grows on plants that are fairly narrow at base, widening to about 3-5½ feet across at the top. Their leaves are generally long, lobed, serrated at the edges, and dark green or green mottled with silver. Summer squash is sown and harvested when soil and air temperatures are warm. Its flavor is best when picked and eaten at its immature stage; that is, before the seeds are fully developed and while the outer skin is still soft and tender.

Winter squash grows most often on big, vigorous vines or on a semi-bush. Leaves of the winter squash often exceed 15 inches or more in length and width, are generally round and may be matte or glossy-surfaced. Winter squash has an assortment of fruit size and shapes. They may be spherical, oval, or acorn shaped. The skin can be smooth, warty, or grooved and the color varies from white, yellow or orange to green, blue or black. Winter squash needs warm weather for germination and fruit set, but requires cool nights as it reaches maturity. This is necessary for sugar to accumulate and produce the sweet flavor winter squash is known for. These varieties require a longer growing season and are harvested when fruits are mature with fully developed seeds and a hard rind.

Summer Squashes:
Crookneck/Straightneck, Scallop/Patty pan, Zucchini (above), Vegetable marrow

Winter Squashes:

Acorn (above), Banana, Buttercup, Butternut, Delicata, Delicious, Hubbard (below) 

Miscellaneous Squashes:

Edible Gourds, Turban, Vegetable Spaghetti


Planning Your Garden
The first step in planning is to choose a sunny location, as squash needs full sun all day to mature and set fruit. Squash requires more space than many other garden vegetables, so advance planning is worthwhile.

Summer and winter squash have different space needs and will be discussed separately.

Most summer squash varieties have a bush habit and many of the newer hybrids have been bred for compact plant size. Plan on four square feet for each plant. This is a relatively early crop, producing fruit in about two months. Summer squash has many culinary uses from salads to stir-fry. However, they do not store well and are best used within several days of harvesting.

Most winter squash have a vining or semi-bush habit, although some newer varieties are bush. Vining types need a larger area than do the bush varieties. Plan on 12 square feet for each vining plant. Small-fruited winter squash can be trained on a 4-foot high trellis. The trellis should be placed toward the rear of the garden so that the vines do not shade other vegetables. Since it takes eighty to one hundred thirty days to produce mature winter squash, these varieties are best suited to areas of North America with a long growing season.

The phrase “growing season” simply means the number of frost free days in an area. The county extension agent can tell you the average dates of the last frost in spring and the first frost in fall. The difference between the two is the length of the growing season. Most seeds must be sown after the last frost in spring and the fruit harvested before the first frost in autumn. Seed catalogs and seed packets print a “days to maturity” designation for each plant variety. The designation includes the number of days from sowing to harvest. For example, if a particular variety takes seventy days to mature and your growing season is greater than seventy days, that variety is suitable for your location.

Because squash has such a long productive season, it is a heavy feeder. To fortify the soil, spade in organic materials such as well-rotted manure or compost before seeding. Later in the growing season, an application of a balanced fertilizer, such as 10-10-10, will replace the necessary nutrients.

Far North Gardens
Although direct sowing is the simplest and most effective way to plant squash, gardeners in the northern zones may wish to start seed indoors. Begin about three weeks prior to the last frost date. As squash has fairly large seeds, sow one seed in each pot. If peat pots are used, they can be planted directly into the garden, thus lessening transplant shock. While indoors, site the pots in full sun or under fluorescent lights; harden off outdoors, then transplant.

Sowing Seeds
There are two main ways to sow seeds in the garden; which the gardener chooses depends on space limitations and personal preference. The first method is planting in a series of hills, leaving 4 feet between hills. To create a hill, mound the earth in a cone shape about 5 inches high. Make a saucer like depression in the top of the mound and plant a half dozen seeds in a circle. Cover the seeds with 1 inch of fine soil or vermiculite. Once seeds have sprouted and grown a full set of true leaves, thin to three plants per hill. If more than one row of hills is desired, space rows 5 feet apart. The use of hills makes it easier for the gardener to walk all around the plants to water, weed and cultivate. In addition, a raised planting area warms the soil and improves drainage.

The second method is row planting. Plan to space the rows 6 feet apart to allow for plant growth, to promote good air circulation and to give the gardener easy access to the plants. Begin by sowing two to three seeds per foot, but thin to one squash about every 2 feet once true leaves emerge. Gardeners who live in areas with at least one hundred fifty frost-free days might consider a second planting of summer squash. Remove the first planting of squash after harvest. Seeding again between July 1 and August 15 will lengthen harvest times and avoid the “Zucchini Bumper Crop Blues” that can afflict many of us in late summer.

Plan to grow squash varieties suited to your climate and growing season as well as to your family’s taste.

Soil Preparation
Squash does best on a well-drained and aerated soil. If your garden site has heavy clay soil, till to improve drainage. Squash prefers soil that is neither too acid nor too alkaline; pH levels of 5.5 to 6.8 are acceptable. To learn the pH level of your garden, contact your county cooperative agency for information on soil testing.

Germination time can be hastened somewhat by presoaking seeds to soften their hard coat. Soak in tepid water for no longer than twenty-four hours; if seeds are allowed to remain wet, they are more susceptible to decay causing organisms. Dry the seed carefully before planting. Delay sowing seed until after danger of frost is past and soil temperature has warmed up to a minimum of 70ºF. At a soil temperature of 80ºF, seeds should sprout in three to five days.

Cultivation of squash is not difficult, provided the gardener remembers a few basic requirements. Winter squash is fairly drought resistant once the plants are established, but summer squash needs a regular water supply during its blossom and fruit development. Both types should receive enough water weekly, either through rain or irrigation, to wet the soil to a depth of 10 to 20 inches. Drip or ground irrigation is preferable to overhead watering because wet leaves may encourage the formation of foliar diseases such as mildew.

The use of black plastic mulch, especially for bush varieties, can cut down the need for frequent weeding. It may be difficult to put plastic mulch down in areas where running vine types are grown. Organic materials, such as grass clippings or straw, can be used and have the advantage of improving the soil when spaded into the garden at the end of the growing season. Keeping the garden area weed free will ensure that tender seedlings do not have competition for water and nutrients. Squash leaves grow rapidly and will shade out many weeds by mid-season. Spaces between rows can be hoed, but because leaf stalks are brittle and tender, it is advisable to hand weed close to the plants.

Gardeners sometimes wonder why many squash flowers do not set fruit. Separate male and female flowers are produced on the same plant or vine, but only the female flowers bear fruit. Female flowers grow on short stalks and have a bulge, the miniature squash, below the petals. Bees serve as the primary means of pollinating the female flowers.

Zucchini Summer Squash ‘Portofino’

Summer squash is harvested at an immature stage when the seeds are small and the skin is tender. One test of tenderness is to pierce the skin of the vegetable with your thumbnail. If the skin breaks easily, the fruit is still tender. Squash can be picked any time. Many gardeners prefer the baby or miniature size squash, which is harvested with the blossoms still on the fruit. If the fruit is picked frequently the plant will be encouraged to continue production. It’s easy to miss young fruit hidden by the large leaves. Walk through your patch every few days and lift leaves to see what has been hidden. Some gardeners prefer yellow or white squash since they are easier to spot amid the green foliage. Should summer squash become large however, all is not lost. If the squash is cut in half lengthwise, and the seeds removed, the fruit can be baked. Summer squash can be kept in the refrigerator for five days, if put in a moisture proof container or plastic wrap.

Winter squash is ready for harvesting when the skin is hard and resists thumbnail pressure. Cut stems 1 or 2 inches from the end of the fruit. Twisting or pulling squash from the vine may break open the fruit and make it easier to decay. Usually squash should be picked prior to the first frost. Squash can also be harvested after the first light frost has killed the foliage; squash can even recover quite well from light frost damage to the fruit, which cause small water soaked spots to appear. If the squash has been subjected to temperatures below 50ºF for two weeks, the squash may break down and rot in a few weeks.

Does winter squash need to be cured before storage?
Some sources say winter squashes can be cured to dry and harden their shells completely before they are stored. Also, curing speeds the conversion of starches to sugars, improving the eating quality. Winter squashes that can be cured are butternut, delicious, and hubbard. Acorn types are not recommended for curing. To cure, put squash in a warm, (75-80ºF) well-ventilated place, such as near a furnace or wood stove, or on a sunny, enclosed porch for a week or two. One expert says the higher temperature curing process can be skipped if you can keep a long-term storage temperature of 50-55ºF. Curing also can reduce storage life. Another source recommends picking the squash only when the rinds are well hardened and storing it in a dry, moderately warm place, such as on shelves in a dry basement that has a furnace.

Storage Techniques
The National Garden Bureau recommends storing winter squash at 50-55ºF with humidity of 50 to 75 percent. The storage location should have good air circulation, a uniform temperature and humidity. Under good storage conditions, gardeners can expect acorn squash to store ten to fifteen weeks. Other winter squashes can last up to six months in storage.

Zucchini is lower in calories than many popular summer fruits and vegetables. Corn, tomatoes and watermelon each pack more calories than zucchini’s 22 calories per cup. As summer’s bounty wanes, turn to winter squash for an excellent source of Vitamin A and minerals. Cancer researchers now believe that proper diet may have a strong role in reducing the risk of certain cancers. Research has focused on foods containing Vitamin A and beta-carotene; a precursor of Vitamin A. Beta-carotene is found in yellow and orange vegetables, such as squash. Although about the same in caloric value as potatoes, winter squash contains more than twice the potassium as potatoes.

Clean, well-maintained gardens are less likely to be infested with pests or infected with diseases. At all times of the year, keep growing areas free of perennial weeds, garden residues and trash. If a plant is badly infected, remove it from the garden, but do not add to the compost pile. After harvest, destroy squash plants to prevent over wintering of pests or viruses.

The National Garden Bureau found three pests that might be a problem to gardeners. They are the striped cucumber beetle, the squash bug and the squash vine borer. Each pest will be discussed for identification and suggested control.

The striped cucumber beetle begins as a white, slender larva with brownish ends. It grows to be an adult about ¼ inch long, yellow to black, striped or spotted. The beetle causes damage in several ways. In the larval stage, it feeds on roots underground. In the adult stage, it feeds on stems, leaves, fruit, and on young plants, which can wilt and sometimes die. The adult beetle carries two diseases of squash, bacterial wilt and squash mosaic virus. Starting seeds or transplants under a cold frame, or covering young plants with netting will help to keep beetles off. Till the soil in the spring to expose any hibernating adults.

As a nymph, the squash bug varies from bright green with a red head and legs, to dark greenish-gray with a black head and legs, and is about 3/8 inch long. As an adult, it is a flat, brownish-gray bug, about 5/8 inch long. Squash bug clusters are shiny brick red and can be found on the undersides of leaves and on stems and unripe fruit. The squash bug does its damage by sucking the juice from leaves and stems, which will wilt and dry up. Young plants are especially vulnerable.

Control this pest by picking up any bugs or egg masses you see on leaves. Lay boards on the ground near plants, bugs will gather under the boards at night. In the morning, lift the boards and destroy any bugs you find.

The squash vine borer is a problem east of the Rockies. The larvae of this pest are up to an inch long, wrinkled, and white with a brown head. Larvae are hatched from eggs laid on stems near the base, in late spring or early summer, by a clear-winged moth. Hatched larvae eat holes in the stems, causing individual stems or the plant to wilt or die. Signs of vine borer infestation include a sudden wilting of the stem, small borer holes at the base of the stem, and green sawdust like material inside stems or in piles near the borer holes.

Watch for, scrape off, and destroy any egg clusters found on stems or undersides of leaves. Split the stem lengthwise and remove or kill the borer. Cover the split with a moist mound of dirt to prevent drying and to induce root growth beyond the point of injury, or wrap the split with gauze and water well. Cut off and destroy very badly damaged stems. Prevent moths from laying eggs by spreading shiny foil under plants in late spring and early summer. The sunlight will reflect to confuse the moths.

Bacterial wilt causes a sudden wilting and drying up of squash vines and plants. The bacteria enter the plants and plug up the water vessels of the stems and leaves. Wilting will first be seen in the leaves of the plant. In the early stages of disease, the leaves may wilt in the daytime and then recover at night. Young plants will die rapidly, while older plants may at first be affected only in one stem. Wilt can also cause fruit to wither. The presence of bacterial wilt is indicated by a white, sticky, stringy substance seen when a stem is sliced and pulled apart.

Patty pan Summer Squash ‘Moonbeam’

Bacterial wilt is totally dependent on the cucumber beetle to transmit the bacterium that causes the disease. To control disease, therefore, it is necessary to control the cucumber beetle.

Viruses are indicated by yellowish-green, mottled leaves, stunted vines, and warty, deformed fruit. New leaves may die and plants may decline. Most virus or mosaic disease on squash is caused by cucumber, watermelon or zucchini yellow mosaic viruses. The virus survives in perennial weeds, in the soil, or in the seed of infected plants. Like bacterial wilt, it is spread by aphids or chewing insects such as cucumber beetles. It can also be spread by a gardener moving through or working in the garden under wet or moist conditions, such as after watering.

Powdery mildew is a fungus disease occurring all over the U.S. A powdery white growth appears on the upper surface of the leaves, which will turn yellow and die. The mildew competes with the plant for nutrients, reducing yield and perhaps even killing the plant. Older leaves are affected first. Powdery mildew spreads rapidly and is carried by the wind. It can occur under any weather conditions, but wet or dewy leaves encourage its development. Under warm temperatures it can become a serious problem. To control, strip off older leaves.

Future Breeding
The breeding objectives to be achieved are improved disease/virus tolerance, multiple disease resistance, and in the more distant future, insect and pest resistance. Breeders are increasing the color range of squash fruit, looking for unique or decorative colors. Also important, is to change the plant habit from a vining habit that extends 12 feet to a compact bush habit needing only 2 square feet of garden space. Earliness and yield are primary considerations for all experimental lines prior to an introduction of a new cultivar. Look for more squash cultivars that can be harvested early and used as summer squash, or if left on the plant, the squash forms a protective skin for storage like a winter squash.

This squash fact sheet is provided as a service from the National Garden Bureau.

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