Squash and Pumpkins

The cultural requirements of squash and pumpkins are similar and there is often  great confusion in differentiating the two. T.W. Whitaker and G.W. Bohn presented evidence in 1950 that five species of Cucurbita, known as pumpkins and squash, originated in the Americas. They defined the terms pumpkin, summer squash, and winter  squash as follows: Pumpkin: the edible fruit of any species of Cucurbita used when ripe as a table vegetable or in pies; flesh is somewhat coarse and/or strongly flavored, hence is not generally served as a baked vegetable. Summer Squash: The edible fruit of any  species of Cucurbita, commonly C. pepo, used when immature as a table vegetable. Winter Squash: The edible fruit of any species of Cucurbita used when ripe as a table vegetable or in pies; flesh is usually fine-grained and of mild flavor, hence it is suitable for baking.

Only the female flowers produce fruit; male and female parts are in separate flowers. Male flowers emerge first, followed by the females.

Climate Requirements

Most pumpkin and squash seeds will not germinate satisfactorily in cold soil and the plants are injured by light frosts. Planting should be delayed until the soil has warmed to 68oF and all danger of frost has passed. Plant at a depth of 4 inches The use of summer squash transplants should be considered if early harvest is important.

Fertilizer and Lime

It is best to base fertilizer and lime applications on soil test results. General recommendations, when using black plastic mulch, would be 1 pound of actual nitrogen, 2 pounds of phosphorus, and 3 pounds of potash per 1,000 square feet. On bare ground, increase the amount of nitrogen by 25 percent. It is best to do this as a sidedress application when vines begin to run. Lime should be applied only if indicated by a soil test in order to maintain a pH between 6.5 and 6.8.

Culture

The use of black plastic mulch will conserve moisture and help control weeds. Spacing of the plants or seeds in the row depends on growth habit of the vegetable. For bush-type squash and pumpkins, hills of two plants should be spaced 3–4 feet apart with rows on 4–5 foot centers. For vining types, hills of two plants should be spaced 5 feet apart with rows on 7-foot centers. The vining types of squash and pumpkins need the extra space and will invade even more space if allowed, so plan and plant accordingly.

Insects and Diseases

Important insect pests of pumpkin and squash are the squash bug, squash vine borer, cucumber beetle, and  aphids. Important diseases are powdery mildew, downy mildew, angular leaf spot, black rot, gummy stem blights,  mosaic viruses, and bacterial wilt.

Harvesting and Storage

Summer squashes of all types and varieties should be harvested when they reach a size of 4–6 inches long  and 1½–2½ inches in diameter. This ensures high-quality fruit and additional fruit production. High-quality winter squashes and pumpkins are associated with maturity so they should not be harvested until they are fully ripe. Fruits subjected to a hard frost will not keep; harvest should be completed before cold weather. A portion of the stem is usually left attached to the pumpkin or squash at harvest time.  Halloween pumpkins are most attractive when a stem or "handle" is carefully allowed to remain.

Store only those fruit that are free of cuts, wounds, and insect or disease damage. Immediately after harvest the fruit should undergo a ripening or curing process to harden the shell. A curing period of about two weeks at 75–85 oF with good circulation is desirable. Store at 50–70 oF with humidity between 50 and 70 percent.

Adapted from Ted W. Gastier, Ohio State University Extension, 2000