Pumpkin

Pumpkins are warm-season annual vines that trail along the ground or climb with tendrils. Plants sold as pumpkins belong to several Cucurbita species, and the fruit comes in many colors, shapes and sizes, mostly orange when ripe. Some types are grown for carving and some for pies, and certain giant cultivars can exceed 200 pounds (about 90 kg).

Sowing. Sow seeds outdoors after the danger of frost has passed. Seeds are easily sown from seed especially when soils are warm. Some growers start seeds indoors two to three weeks before the last expected frost, then harden seedlings off for a week before planting. Sow two or three seeds per hill or pot and thin to one plant once the first true leaves appear.

Depth and spacing. Advice on sowing depth differs. One extension guide says about ½ inch (1.3 cm) deep, while another says 1 to 2 inches (2.5 to 5 cm) deep in mounds. Spacing also varies: rows 8 to 12 feet (2.4 to 3.7 m) apart with one plant per spot, or transplants 2 to 3 feet (61 to 91 cm) apart in rows 4 to 6 feet (1.2 to 1.8 m) apart.

Sun and transplants. Pumpkins need at least 6 hours of direct sun a day. You can also transplant in late spring, early summer or after the last frost. Start transplants indoors in 3-inch containers about 3 weeks before planting time. Black plastic mulch warms the soil and can speed maturity.

Watering. Water deeply and regularly at the base of each plant, especially in hot, dry weather and once fruit starts to form. Plants need about 1 inch (2.5 cm) of water per week. USU advises 1 to 2 inches (2.5 to 5 cm) per week and drip irrigation where possible.

Feeding and weeds. Pumpkins have a high need for nutrients, so fertilize before planting and side-dress when fruits first develop. Avoid high-nitrogen fertilizers, which may inhibit flower initiation or fruit growth. Use mulch around plants and remove young weeds by hand or with a hoe.

Common pests include aphids, squash bugs, cucumber beetles and slugs. UMD also lists squash vine borers, squash beetles, downy mildew and powdery mildew. Powdery mildew starts as white patches on older leaves, and virus-infected plants look mottled and curled; control aphids and destroy badly infected plants.

Pollination. Male flowers appear one to two weeks before female flowers, and bees must carry pollen to the female flowers. Poor fruit set is common in rainy weather when bees are inactive. Avoid pesticides during bloom to protect pollinators.

Pumpkins are usually harvested in late September or October, before heavy frosts. Cut them with a sharp knife or pruners, leaving 3 to 4 inches (7.6 to 10 cm) of stem on each fruit, and avoid bruising. A mature pumpkin has a hard rind that resists scratching from a fingernail.

Light frost kills the vines but does not damage the skin or flesh; temperatures under 28 °F (−2 °C) could injure fruit. Sources give different timelines: USU says 45 to 55 days after flowering, while UMD says most pumpkins need more than 100 days to ripen.

Store pumpkins in a dry area between 50 and 55 °F (10 to 13 °C). Keep them where they will not freeze. Pumpkins store well only when the rind is hard and firm.

Gardening experts listing describes this plant as non-toxic for cats and dogs. Do not read that pet rating as applying to people. No toxicity rating for people is given for this plant in these pages.