Ornamental pumpkins vary in size from less than a pound to over 500 lbs., depending on the type and particular variety. Market demands determine the desired size. In some markets, uniform size is an important aspect of quality. Production of extremely large pumpkins (over 500 lbs.) is a specialty demanding intensive management of individual pumpkin plants and fruit.

Plant population influences fruit size, with higher populations producing smaller fruit, on average. Changes in spacing between plants within a row have a greater impact on fruit size than changes in between-row spacing. Plant population recommendations may be found in the Midwest Vegetable Production Guide, or through your local Cooperative Extension Service.

Drought stress, especially during fruit development, will limit fruit growth.

Diseases, insects and weeds can reduce fruit size. Control recommendations for commercial growers may be found in the Midwest Vegetable Production Guide, or through your local Cooperative Extension Service.

The stem or peduncle, which attaches the pumpkin fruit to the vine, is a critical part of a jack-o-lantern pumpkin. A strong, green peduncle is essential for a high quality jack-o-lantern. A peduncle that is easily broken or detached from the fruit is undesirable. The length and width of the peduncle should be proportional to the size of the fruit: while a length of 2 inches may look balanced on a pie pumpkin, a length of 4 or 5 inches would be better for a 20-lb. jack-o-lantern. Pumpkin varieties differ greatly in peduncle quality.

Insect feeding or diseases such as powdery mildew and plectosporium blight can weaken a peduncle. Control recommendations for commercial growers may be found in the Midwest Vegetable Production Guide, or through your local Cooperative Extension Service.

The shape of a pumpkin is governed by genetics. Market demands determine desirable shapes. Currently, for jack-o-lantern types the most desirable shape seems to be a little taller than wide. Fruit that is asymmetrical is considered to be lower quality in wholesale markets. Misshapen pumpkins may result from physical obstruction during growth of the fruit. For giant pumpkins, flattened and lopsided shapes are typical and the market does not demand uniformity. Niche markets exist for unusual shapes such as the flattened and strongly sutured Cinderella types like the variety 'Rouge vif d'Etampes'.

Pumpkin color is important in ornamental markets. Deep orange is generally favored for jack-o-lantern pumpkins at this time. The genetic background of the pumpkin is a major factor in determining fruit color. Most jack-o-lantern varieties are green when immature and turn orange at maturity. Some varieties are yellow when immature and turn orange at maturity. Giant pumpkins are typically yellow or whitish when immature and turn pink-orange to bluish-gray at maturity. Niche markets exist for unusual pumpkin colors such as white or tan.

Warm temperatures speed pumpkin fruit maturation and color development. As air temperatures drop in late summer, the warmth from sunlight on one side of a pumpkin will cause it to turn orange more quickly than the side in the shade.

Use of herbicides containing the active ingredient clomazone can cause lighter fruit color in giant pumpkin varieties belonging to the species Cucurbita maxima, including many of the giant pumpkins.

Fruit infected with one or more viruses often fail to turn completely orange, with the green remaining as speckles or spots. Occasionally, this may be considered attractive and of higher quality, but more typically pumpkins with severe virus symptoms are not marketable.

Fruit harvested before it has turned completely orange will continue to turn color, but green areas will not develop the full color of a pumpkin left on the vine.

Insect Damage on Pumpkin Fruit