Growing Squash in Iowa

Summer and winter squash are some of the most popular vegetables in the home garden. Summer squash can be eaten raw in salads, stir-fried, steamed, or cooked in various dishes. Winter squash can be baked, steamed, or boiled.

Types | Suggested Varieties | Planting | Care | Potential Problems | Harvesting & Storing | Squash Blossoms | More Information

Types of Squash

Summer Squash

Summer squashes are large, bushy plants. The fruit of summer squash are harvested when they are immature and have soft skins. Fruit can be stored for 1 to 2 weeks. There are several types of summer squash. These include zucchini (cylindrical, club-shaped fruit), crookneck (long, tapered fruit with curved necks), straightneck (bottle-shaped fruit with straight necks), and scallop (flattened, roundish fruit with scalloped edges).

butternut squash — Butternut Squash. Photo by Cindy Haynes

Winter Squash

Most winter squashes are large, vining plants. (Several semi-bush varieties are available to individuals with small gardens.) Fruit are harvested when they are mature and have hard rinds. Winter squash fruit can be stored in a cool, dry location for 1 to 6 months. Various sizes, shapes, and colors of winter squash are available. These include acorn, buttercup, butternut, and Hubbard.

Suggested Varieties

Summer Squash	Winter Squash
Dixie - yellow crookneck	Blue Hubbard
Elite - zucchini	Burgess Buttercup
Goldfinger - golden zucchini	Butternut Supreme
Jaguar - zucchini	Sweet Mama - buttercup
Seneca Butterbar - yellow straightneck	Table Ace - acorn
Spineless Beauty - zucchini	Table Queen - acorn
Sunburst - yellow patty pan (scallop)	Vegetable Spaghetti

Planting

developing winter squash on vine — Developing Squash on Vine

Summer and winter squash perform best in fertile, well-drained soils containing high levels of organic matter. They also require full sun. Organic matter levels can be increased by incorporating well-rotted manure or compost into the soil. If a soil test has not been conducted, apply and incorporate 1 to 2 pounds of an all-purpose garden fertilizer, such as 10-10-10, per 100 square feet prior to planting.

Summer and winter squash are commonly planted in hills. Sow 4 to 5 seeds per hill at a depth of 1 inch in mid-May in central Iowa. Thin to 2 to 3 vigorous, well-spaced plants per hill when seedlings have 1 or 2 true leaves. The last practical planting date for summer squash is July 20. Winter squash must be planted by June 10.

For an early crop, start plants indoors 3 to 4 weeks prior to the anticipated outdoor planting date. Since squash seedlings don't tolerate root disturbances during transplanting, start seeds in peat pots, peat pellets (Jiffy 7's), or other plantable containers. Sow 3 to 4 seeds per container. Later, remove all but 2 seedlings. Harden the plants outdoors for a few days in a protected location prior to planting to lessen transplant stress.

Hills and rows of summer squash should be 3 to 4 feet apart. Hills of winter squash should be spaced 4 to 5 feet apart with 5 to 7 feet between rows.

Care

Control weeds with frequent, shallow cultivation and hand pulling. Water plants once a week during dry weather. Avoid overhead watering which can promote powdery mildew in some varieties. Scout frequently for insect pests and address those pests as soon as they are noticed.

Variety of winter squash — A variety of winter squash in the fall. Photo by Cindy Haynes.

Potential Problems

Squash Bugs

Squash bugs have piercing-sucking mouthparts. Heavy feeding causes entire leaves to wilt, turn brown, and die. Several methods can be used to control squash bugs in the garden. Adults and brick red egg masses on the undersides of leaves can be removed by hand. Adults can also be trapped under boards or shingles placed under the plants. Turn the objects over daily and collect and destroy the hiding squash bugs. Small, immature squash bugs (nymphs) can be controlled with insecticides, such as carbaryl (Sevin). In fall, remove and destroy plant debris to deprive squash bugs of overwintering sites.

Squash Vine Borer

Squash vine borer larvae bore into squash stems near ground level. Larvae feeding within the vines eventually causes the plants to wilt and die. Squash vine borers can be controlled with applications of insecticides (rotenone, permethrin, or malathion) at regular intervals beginning in mid-June. Apply the insecticide to the base of the vines. After the final harvest, remove and destroy the plant debris. Rototilling in fall or spring may destroy overwintering pupae in the soil.

Zucchini that is too large — Summer squash should be harvested young and small. This zucchini is much to large and will be tough and full of seeds.

Harvesting & Storing

Summer Squash

Harvest long-fruited summer squash varieties when they are about 2 inches in diameter and 6 to 12 inches long. Scalloped types are best when 3 to 5 inches in diameter. Fruit should have soft skins (rinds) that are easy to puncture with a fingernail. Seeds should be soft and edible.

Store fresh summer squash in the refrigerator crisper in plastic storage bags or rigid containers to retain moisture. Stored in this manner, squash will maintain quality for 5-7 days. Summer squash can also be frozen or pickled for longer-term storage.

Winter Squash

Mature winter squash have very hard skins that can't be punctured with the thumbnail. Additionally, mature winter squash have dull-looking surfaces. When harvesting fruit, leave a 1-inch stem on winter squash.

After harvesting, cure winter squash (except for the acorn types) at a temperature of 80 to 85°F and a relative humidity of 80 to 85%. Curing helps to harden the squash skins and heal any cuts and scratches. Do not cure acorn squash. The high temperature and relative humidity during the curing process actually reduce the quality and storage life of acorn squash.

After curing, store winter squash in a cool, dry, well-ventilated location. Storage temperatures should be 50 to 55°F. Do not store squash near apples, pears, or other ripening fruit. Ripening fruit release ethylene gas which shortens the storage life of squash.

When properly cured and stored, the storage lives of acorn, butternut, and hubbard squash are approximately 5 to 8 weeks, 2 to 3 months, and 5 to 6 months, respectively.

Squash Blossoms

The flowers of both summer and winter squash are edible. They can be eaten raw or cooked. They are typically cooked by battering and frying or stuffing and frying. Harvest the flowers on the day they open and use them the same day or within a day or two. Clean blooms carefully under cool water as they bruise and tear easily. Most recipes instruct you to remove the stamens from the inside of the flower with scissors or by twisting off the base of the bloom.

Harvest only male flowers. Harvesting female flowers will reduce squash yields. Be sure to leave behind a few male flowers to pollinate the female flowers, but there are often more than enough male flowers to pick and eat. You can distinguish male flowers from female flowers by looking at the base of the bloom. The base of a female flower will have a bulge just below the petals that looks like a tiny version of the squash. This is the ovary that will develop into the fruit. Male flowers will have a thinner stem below the flower and no bulge (ovary) at the base of the petals.