Why Did My Pumpkin Stop Growing?

Cold Weather

Planting pumpkins too early in the spring may result in poor germination or stunted growth. Lay black plastic over the soil two weeks before planting to warm the soil, and plant pumpkin seeds only after the last expected frost when daytime temperatures are predictably above 75 degrees Fahrenheit. Pick pumpkins in the fall before the first heavy frost. Pumpkins are ripe when the rinds are hard and brightly colored. Pumpkins left in the garden after a frost become soft and rot quickly.

Pumpkins need full sun and adequate soil moisture to grow. Water them weekly during hot, dry weather, reducing water as fall approaches to harden the rinds. Dig 2 inches of compost or manure into the soil before planting pumpkins and fertilize them mid-season with a nitrogen fertilizer. Apply 1/2 cup of a 46-0-0 fertilizer for each 25 feet of pumpkin row. Give pumpkins plenty of room since they grow on long, vigorous vines and overcrowding can stunt growth. Plant pumpkins at least 3 to 4 feet apart.

Non-selective insecticides kill bees and other insects that pollinate pumpkins, potentially reducing yields. Hand pick and destroy beetles, spray aphids and leaf hoppers with insecticidal soap and treat caterpillars with Bacillus thuringiensis (Bt), a biological control that kills only caterpillars. Don't fertilize pumpkins with weed and feed formulas because the herbicides in these formulas will kill pumpkins. If you apply herbicides to other areas of the garden, apply them carefully on a windless day. Herbicides may drift onto desired plants, killing them or stunting their growth.

A common reason pumpkins stop growing is vine damage. The vines are fragile and easily damaged by foot traffic. Once the vine is damaged or the pumpkin is severed from the vine, growth halts. Squash vine borers eat their way through the vines and can eventually kill the plant. Wilted leaves are usually the first sign. Remove infected plants and destroy them. Powdery mildew is a fungal disease that causes white, powdery growth on the leaves, vines and even the fruit. Left untreated, it can stunt growth or even kill pumpkins. Plant disease-resistant varieties and space plants so air circulates freely to minimize the risk of disease. Several fungicides are available for treating powdery mildew, including a natural baking soda product.