History and Taxonomy:

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 is suitable for baking.

Climate:

Most of the seeds of pumpkin and squash 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 68 degrees F at a depth of four inches and all danger of frost has passed. The use of summer squash transplants should be considered if early harvest is important.

Fertilizer and Lime:

Fertilizer and lime applications are best based on soil test results. General recommendations, when using black plastic mulch, would be one pound of actual nitrogen, two pounds of phosphorus and three pounds of potash per 1,000 square feet. On bare ground, increase the amount of nitrogen by 25 percent. This would best be done as a sidedress application when vines begin to run. Lime should be applied only if indicated by a soil test so as to maintain a pH between 6.5 and 6.8.

Culture:

The use of black plastic mulch will conserve moisture and help control weeds in the row. Spacing of the plants or seeds in the row depends on the growth habit of the vegetable. For bush type squash and pumpkins, hills of two plants should be spaced three to four feet apart with rows on four to five foot centers. For vining types, hills of two plants should be spaced five feet apart with rows on seven 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. See GreenShare Factsheets on these specific pests and diseases for more information and control recommendations.

Pollination:

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

Harvesting:

Summer squashes of all types and varieties should be harvested when they reach a size of four to six inches long and 1.5 to 2.5 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.

Storage of Winter Squash and Pumpkins:

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 to 85 degrees F with good circulation is desirable. Store at 50 to 70 degrees F with humidity between 50 and 70 percent.

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