Giant Pumpkin

Overview. Giant pumpkin is Cucurbita maxima, a warm-season annual vine in the cucumber family. The vine trails along the ground or climbs with tendrils, and it is an aggressive grower that is easily started from seed. For very large fruit, choose a cultivar bred for size, such as ‘Dill’s Atlantic Giant’, ‘Prizewinner’, ‘Big Max’ or ‘Big Moon’. Some of these are pumpkin-like squash rather than true pumpkins, and they are generally not used for cooking. Big Max and Big Moon can produce fruit over 200 pounds (90 kg), and giant pumpkins have been recorded at more than 1,000 pounds (450 kg).

Varieties. Results depend on the cultivar, so pick one known for size before you buy seed.

Sowing. Sow outdoors after all danger of frost has passed and the soil has warmed. Seeds are expected to sprout in 7 to 10 days, and the seed supplier gives a germination temperature of 75 to 95 °F (24 to 35 °C). Mound up soil in the middle of the planting spot and plant 3 to 5 seeds about ½ inch deep. Some extension guidance gives a depth of 1 to 2 inches (2.5 to 5 cm) instead, so the depth is not settled. When the plants have their second set of leaves, keep the strongest one and cut the others at soil level instead of pulling them.

Starting indoors. Seeds can be started indoors two to three weeks before the last expected frost. Harden the seedlings off outdoors for about a week before planting them out.

Site and spacing. Choose full sun, with at least 6 hours of direct sunlight a day, in rich, fertile, well-drained soil. Give them plenty of room: 20 to 25 feet (6.1 to 7.6 m) between plants is not unusual for world-champion pumpkins. Home guides space rows about 8 to 12 feet (2.4 to 3.7 m) apart.

Watering. Pumpkin plants need about 1 inch (2.5 cm) of water per week, ideally in the morning so the leaves dry during the day. Another guide advises 1 to 2 inches (2.5 to 5 cm) per week, applied deeply and infrequently. Mulch around the plants to hold moisture and keep weeds down.

Feeding. Feed with a complete fertilizer every week, and avoid high-nitrogen types, which may hold back flowers or fruit. Too much fertilizer can cause excess vine growth and split fruit.

Choosing fruit. When the young fruits are 6 to 8 inches (15 to 20 cm) across, keep the largest and fastest-growing one and remove the rest. Pinch back the vine ends to send energy into that fruit. Another guide suggests keeping two or three fruits on separate runners instead. Place cardboard under the fruit to help prevent soil rot.

Pests. Slugs, aphids and beetles are common pests. Cucumber beetles, squash bugs and squash vine borers also attack these plants. Squash bugs suck sap from leaves, and cucumber beetles can spread bacterial disease.

Diseases. Plants may be susceptible to slugs and snails, grey moulds and powdery mildew. Powdery mildew starts as white fungal patches on older leaves, and as the foliage dies it can expose fruit to sun and cause early ripening.

Harvest. Pumpkins are usually picked in late September or October, before heavy frosts. Cut them with a sharp knife or pruners and leave 3 to 4 inches (7.6 to 10 cm) of stem on each fruit. Fruit is generally ready about 45 to 55 days after flowering, when the vine begins to die back and the rind is hard enough that a fingernail won’t scratch it.

Frost. A light frost won’t harm the skin or flesh of the fruit but will kill the vines, and temperatures under 28 °F (-2 °C) could injure fruit.

Storage. Store fruit in a dry area that stays between 50 and 55 °F (10 to 13 °C). Keep the fruit where it won’t freeze.

Handling. Wear gloves and other protective gear when handling the plant.

Bitter fruit. If a crop tastes bitter, don’t eat it or feed it to pets.

Pets. One page lists the plant as non-toxic for cats and dogs, but the bitter-fruit caution above still applies.