Postharvest handling of pumpkins and winter squash

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Pumpkins and winter squash are maturing somewhat erratically as a result of the cool weather this summer.  As fruit matures, it is often difficult to decide when to cut the fruit from the plants. If there is a wide range of maturity in the field, it may require several trips across the field to cut off mature fruit. All fruit should be cut from vines when the fruit is mature and the handle is still intact. If left attached to the vines, foliar diseases can move into the handles and fruit. The incidence of foliar diseases in the field has a direct effect on the potential quality and longevity of the fruit.

Pumpkins and squash are warm-season crops, and require a long, warm, sunny growing season to reach maximum size and yield. In a cool summer, such as we have just experienced, the rate of growth is reduced and fruit require extra time to reach full maturity. However, when plants begin to deteriorate rapidly from powdery mildew and other foliar diseases, it is time to harvest.

Pumpkins and winter squash are mature when the color of the skin turns from green to their mature color. Jack-o-lantern pumpkins have a shiny, bright orange skin when mature. When the fruit are mature, they should be cut from the vines to let the curing process begin. Curing of pumpkins and squash is a very important part of the post harvest process and should always be included in the crop plan. Removing fruit from the plants reduces the chance that healthy handles will become infected with any of the common rotting fungi that infect the plants.

Curing allows the fruit to shrink about 10 percent in weight, which results from loss of some water. During the process, cuts and bruises heal, and fruit infected with pathogens rot. (If shipped immediately off the field, these infected fruits often rot at retail outlets, and growers have to retrieve them or pay for removal.) Fruit should be kept above 70°F for about two weeks for optimum curing. Warm, sunny weather in the field is the best method of curing.

Pumpkins and squash are very susceptible to cold temperatures, and exposure to temperatures below 40°F will shorten shelf life. Never place pumpkins or winter squash in refrigerated storage below 50°F. A cool night or two in the field won’t do much damage, but a frost can cause discoloration of fruit skin and eventual rot. Storage in refrigeration results in rotten fruit.

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