Squash Top Ten Questions

The squash family has hundreds, perhaps even thousands, of different varieties. Many are great for eating raw or useful in cooking and baking. Pumpkins are closely related to what we call squash; sometimes the same fruit is called a pumpkin and at other times a squash. The following questions give gardeners a few tips on taking care of squash and pumpkin plants.

What's the difference between summer and winter squash?

Gardeners classify squash and pumpkins into two major groups:

Summer squash includes Crookneck, Patty Pan, Straightneck, and Zucchini varieties. They are harvested when they are immature and tender, and have a limited storage life after picking. Most summer squash grow on short, bushy plants and are suitable for the average home garden. Summer squash require 50 to 60 days before harvest. Zucchini is probably the easiest squash to grow, the most productive, and has manageable plants.

Winter squash includes Acorn, Buttercup, Butternut, Delicata, Hubbard, Kobocha, Pumpkin, Spaghetti, Sweet Dumpling, Turban, and Banana varieties. They become fully ripe before frost, so their hard skins make them suitable for up to six months of long-term storage. Most winter squash grow on vines, require a great deal of space, and are best grown in large gardens. However, some winter squash and pumpkin varieties have been bred to produce smaller, more compact plants. Winter squash usually need between 90 to 110 days to grow before harvest. While Banana varieties can grow to over 40 pounds, world record pumpkins can weigh in at over 2,000 pounds!

How many squash plants do I need to feed my family?

Summer Squash: Grow 1-2 plants per person, or 4 plants per family of 4.

Winter Squash or Pumpkin: Grow 1 plant per person.

Grow more if you have a favorite variety, or plan to freeze, dry, or preserve some of the harvest for winter use.

How do I plant the squash seeds?

Start with a soil test. This will give you valuable information about any nutrient needs your soil may have. Adding too much of a nutrient can be worse than too little. Ideal soil pH is between 6.0 and 6.5, although soils with neutral or slightly higher pH produce good crops.

Improve the soil before planting by adding large amounts of compost or well-rotted manure. If enough organic material is added, more fertilization may not be needed. Later on in the season, the University of Minnesota recommends a side dressing of ½ cup of 46-0-0, one cup of 27-3-3, or three and a half cups of 10-3-1 for each 100 feet of row when the plants begin to vine.

All squash require full sunlight (8 hours or more daily). A soil that drains well, but holds moisture, and is rich in organic matter is ideal. Wait until late May or early June when the soil warms up well (70° F at a 2-inch depth) before planting directly out into the garden. Seeds will not sprout in cold or cool soil. Black plastic mulch over the ground will preheat the soil and allow a few weeks earlier planting. Often, drip irrigation is added before the plastic is laid down. Slits are made in the plastic to enable seed planting. Protect the seedlings with cloches or other devices if frost threatens.

In the family garden, summer squash is generally planted in hills. These are not raised areas of ground, but rather are clusters of 3 or 4 seedlings planted 2 inches apart at a depth of ¾ inch. The hills are spaced 5-6 feet apart. A second planting of summer squash can be sown 3 weeks later. Winter squash is planted in rows with plants 2-3 feet apart within the row, and the rows spaced 5-6 feet apart.

Monitor the plants often for watering needs (1-1 ½ inches per week). Because shallow watering encourages shallow roots, deep watering, thoroughly soaking the soil, is recommended for a stronger root system. Sandy soils, however, will need to be watered more often, but will require smaller amounts at each watering. Water at the base of the plants to avoid wetting the leaves; this helps to avoid fungal diseases. It’s also best to water in the morning so that the foliage dries during the day. Weed carefully to avoid root injury. Clean organic mulch will help retain moisture and can reduce weed problems. If using, delay applying organic mulch until the soil warms to 75° F.

Squash may be started in 3 or 4-inch pots indoors 4 weeks before the planting date. Be sure to toughen up the plants gradually (“hardening off”) before transplanting outdoors. Be aware that the delicate roots of the squash are very injury prone making the plant somewhat difficult to transplant. There should be 3 or 4 mature leaves present before transplanting.

Can I grow squash in a container?

Yes, bush varieties of squashes and pumpkins can be grown in large containers with drainage holes. Put the containers in a spot that receives at least 8 hours of direct sunlight each day. Choose a good quality sterile potting mix. A good potting mix has good drainage and is free of weeds, insects, and disease. Garden soil is unsuitable. It tends to compact, squeezing out both needed air and water. In addition, weed seeds, insects, and disease are often present in garden soil. Check the label on the potting mix for nutrient content. If more fertilizer is needed, some organic fertilizer or slow-release fertilizer may be added. Follow the fertilizer label for recommended amounts. Depending on pot size, limit the number of plants to one or two per pot. A 5-gallon pot is the minimum size for growing squash.

You may need to water more often as soil in pots tends to dry out rapidly; use your finger to test for soil moisture. Monitor the plants every day for water needs and other problems. During hot weather, daily watering may be necessary. Dark colored pots may overheat easily and may need to be shielded against excessive heat with a light-colored material. After flowers form, fertilize weekly with a diluted (50 %) nonorganic or organic fertilizer solution.

If growing summer squash, pick it every other day to encourage the plants to keep yielding.

Why are my squash making flowers but not fruit?

Poor pollination is the likely problem. Squash plants have male flowers and female flowers. For the fruit to form, pollen must be transported from the male flower to the female flower. If there are few bees available, especially on cool and cloudy days, the plants may not get adequately pollinated. The small squash will turn brown and rot on the vine. In some rainy, windy, or very cool years, poor squash pollination and poor yield can’t be avoided.

If your plant is not setting fruit, try pollinating the female flowers by hand. Squash flowers open in the morning and stay open for only a day. To pollinate, pick a fully opened male flower (the longer stemmed flower) in early morning. Remove the petals from the male flower. Dab the yellow pollen of the male flower onto the female flower’s pistil. The pistil is the sticky structure right in the middle of the female flower. Be generous when applying pollen, and a good size fruit will result. A cotton swab or camelhair brush, coated with pollen, may be used instead.

How do I know when the squash are ready to be harvested?

Harvest summer squash when it is 2-3 inches across, and up to 7 inches long. It can be harvested at smaller sizes for even more tender fruit. Leave a short stem attached to the fruit when cutting it off the vine with a knife or pruners. Be careful when handling the fruit, as the skin bruises easily. If a summer squash is overlooked, in less than a week it will grow into a large, seedy war club that causes the plant to stop yielding. Yellow-skinned Zucchini is easier to see amongst the green foliage. Harvest every other day to remove ripe fruit, as well as to examine the plants for water needs, insects, and diseases.

Winter squash is ready 3-4 months after planting. Check to see that the skin is hard; it should be hard to pierce with a fingernail. Cut the squash or pumpkin off the vine with a sharp knife, a small saw, or pruning shears. Leave 3-4 inches of stem on the fruit to protect it and to prevent disease entry during storage. If the fruit is bruised or wounded, use it first as it will not store well. Make sure to pick winter squash before the first frost since freezing will decrease its storage quality.

What are some of the most common insect problems with squash?

Squash vine borers attack summer and winter squash, as well as pumpkins. In late June to early July the female moth emerges from the ground, flies around during the day, and lays eggs at the base of squash plants. The eggs hatch in about 1 week and the larvae burrow into the stem of the squash, feeding for about 4-6 weeks. The borer is a white or cream-colored, brown-headed larva about 1 inch long. The first damage is often the sudden wilting of the vine. You might see holes at the base of the plant with orange or green sawdust-like frass, the insect’s excrement. Control: The female moth is attracted to yellow, so yellow-colored pans filled with water set out in late June will attract the moth and drown it. Infested vines can be cut open lengthwise at the base and the borer killed. Carefully cover the cut vine with soil so that it can take root. A fine pin pushed into the stem, poking at ½ inch intervals, can kill the borer. A late crop may be planted at the beginning of July, when the moths are done with egg laying. Butternut and Zucchini squash are less likely to attract borers since they prefer other squash varieties. Plants may be completely covered with spun fabric to exclude the moth, but it will have to be removed to allow pollination when the squash flowers bloom. This pest is hard to control by chemical means. An insecticide will not penetrate the vine and kill the borer. Pull up and destroy all dead plants.

Squash bugs live in groups of adults and smaller nymphs. They are shield-shaped or roughly triangular-shaped and are dark grey in color. They are sap-sucking insects that feed on the leaves, stems, and fruit. The plant may be killed. Control: Leave boards out at night near the plants; lift the boards in the morning and destroy the insects found. Remove all clusters of tiny football-shaped eggs found on the bottoms of leaves. Pyrethrum and Neem oil can be used for control. Remove or bury all plant debris at the end of the season. Wait 3 or 4 years before planting squash or pumpkins in the same area.

The striped cucumber beetle damages the leaves, flowers, stems, and fruit of squash plants. They can carry bacterial wilt in the gut and can spread the disease to squash family plants. The adult is 1/5” long, yellow green with 3 black stripes on its back. Control: Row covers can be used for early season control but must be lifted for bee pollination when squash flowers appear. Yellow sticky traps will attract and capture the insects. Kaolin clay (“Surround”) is sometimes used to prevent the insects from feeding.

Check with the University of Minnesota website for more information about pesticides for squash insect control, https://extension.umn.edu/yard-and-garden.

What are some of the most common disease problems with squash?

Powdery Mildew is a fungal disease that forms a white powdery growth on the upper surfaces of the leaves. Downy Mildew is another fungal disease that forms small yellow spot on the top of leaves, becoming irregularly shaped brown lesions. A gray mold forms on the bottom of the leaves. Both diseases can harm and kill plants. Control: Fungal diseases can be prevented with fungicide applications. These are a preventative measure and multiple ongoing applications need to be applied before the fungus is present.

Control of disease always starts with good garden sanitation. Planting disease-resistant varieties and using disease-free seed will decrease problems. Avoid overhead watering, as damp leaves provide a favorable environment for disease formation. Water at the base or use drip irrigation, if possible. Choose a soil that drains well. Rotate your vegetable crops and do not plant squash in the same area for 3 or 4 years. Keep the planting weed free to eliminate possible disease hosts that could infect your plants. Do not stress your plants; make sure to provide adequate water and nutrients. Harvest ripe fruit promptly. Destroy or bury vegetable debris.

Blossom end rot can also affect squash plants. It is characterized by dark brown or black leathery lesions on immature fruit at the end farthest from the stem. It is a physiological problem caused by the inadequate uptake of calcium by the developing fruit. Uneven or inconsistent watering, drought, or root damage can lead to the development of this condition. Excess nitrogen fertilizer can promote rapid growth of the plants and can decrease calcium in the soil. Control: Good and consistent watering will decrease the incidence of blossom end rot.

Check with the University of Minnesota website for more information about pesticides for squash disease control, https://extension.umn.edu/yard-and-garden.

How should I store the harvested squash, and for how long?

Summer squash can be stored in a perforated bag in the refrigerator for up to four days. Take care in handling to not bruise or injure fruits.

Before storage, the winter squash or pumpkins need to be “cured,” which is a drying process that toughens up the rind, heals small scratches, sweetens the fruit, and enables longer storage time. Harvest the fruit and wipe off any dirt or debris. Over a period of 10-14 days, let the squash cure in the field, greenhouse, or sunny windowsill rotating frequently to allow all sides to dry. Then store the cured squash or pumpkins in a root cellar or cool dry place. Do not stack the fruit, but separate it for good ventilation. Acorn squash stores well for only a month or two. Other squash store well for two to three months and sometimes up to 6 months; check the condition of the fruit often during the storage period.

What is the proper way to harvest and store winter squash? from Iowa State University Extension

How do I grow giant squash or pumpkin for exhibit at the local fair?

Start with good seed and genetics. It was not until the 1960’s and 70’s that Howard Dill, a Nova Scotia farmer, developed a greatly improved strain of large pumpkin. Today, Dill’s “Atlantic Giant” is the ancestor of world record pumpkins. From that seed, you can grow a 300-pound pumpkin without much effort. Many seed companies still sell this variety. “Atlantic Giant” takes about 130 days to mature. Some growers will sell seed from their thousand-pound giants, but the cost is often $6.00 or more per individual seed.

The largest pumpkins often require 150 or more days to mature and are grown until a fall frost ends all growth. To get the longest growing season possible, start your seedlings indoors in 12-inch peat pots 6 weeks before the last spring frost date. Before setting the plants out, wait until the first true leaves are present and outdoor soil temperature at a 4-inch depth is from 60 to 65 degrees F. Provide protection from cold winds and frost. Black plastic mulch will warm up the soil, reduce watering needs, and keep weeds in control. Install drip irrigation under the plastic. Poke holes in the plastic for water drainage and air penetration. A thick organic mulch may be used instead, but wait a few weeks for the soil to really warm up before applying it.

Choose a planting site in full sun with well-draining soil of neutral or slightly acid pH. Avoid low-lying spots where frost might settle. A soil test will determine the pH and if your soil lacks essential nutrients. Add plenty of compost or well-rotted manure and work it deeply into the soil. Provide plenty of space for growth by allowing at least 25 to 35 feet between plants.

After the first fruits form, remove all but the biggest fruit from each vine. If the temperature reaches into the 90’s, put up a cloth shade for the pumpkin and its vine. This will reduce stress on the plant. Shading also keeps the pumpkin skin soft and pliable, helping to prevent splitting. (Some growers apply baby oil to the pumpkin skin each day to prevent splitting). Overheating on one side of the pumpkin can cause it to explode.

Water carefully every one or two days. Never let the plants wilt, yet never water so much that the soil is over-saturated. Many growers use drip-watering systems and add fish emulsion or other organic fertilizers to their water. Slow release fertilizers tend to keep the plants growing vigorously, but not so fast that the pumpkins split open. Great pumpkins can gain over 50 pounds per day.

So enjoy your squash and pumpkins. If you’re like me, you will inspect, guard, and water them daily. You will baby the pumpkin as if it were your first newborn. You will protect it from all enemies, both foreign and domestic. You may even decide to build a little greenhouse over the plant to ward off cooler weather. And, if you are lucky, you will grow a fair-sized pumpkin, or at least amaze the little kids across the street. Good luck!

References

• Michigan State University (2016), Container gardening with vegetables & herbs
• Texas A & M University (2013), Hand Pollinating Squash
• University of Minnesota Extension (2018), Growing pumpkins and winter squash in home gardens
• University of Minnesota Extension (2018), Growing summer squash and zucchini in home gardens
• University of Wisconsin Extension (2011), A Plain Language Guide Growing Fresh Market Pumpkins, Squash, and Gourds
• Warren, S. (2007), Backyard Giants: The Passionate, Heartbreaking, and Glorious Quest to Grow the Biggest Pumpkin Ever. Learn about the triumphs, failures, and methods as farmers in the tiny state of Rhode Island fiercely compete each year to grow world record pumpkins.