Pumpkin seeds are tender and will not germinate in cool temperatures, so pumpkins must be planted once all danger of frost is past. Pumpkins may be started earlier indoors in small pots, but they must be transplanted with care, since the root systems are very sensitive to disturbance.
Vining varieties require 50 to 100 square feet per hill, spaced at 6-foot intervals. Bush varieties should be planted in hills approximately 4 feet apart. Insert seeds to a depth of 1 inch, at a rate of four to five per hill, and water well after seeding. Once the plants produce their first true sets of leaves, thin them to two or three plants per hill, leaving only the strongest, healthiest-looking seedlings. Pumpkins should be planted in late May in northern latitudes, and late July in southern areas.
Apply fertilizers at a rate of 1 pound of nitrogen per 1000 square feet, working gently into the top layers of soil. Organic fertilizers should be applied at a rate of 2 bushels of manure or 1 cup of bone meal per 100 square feet of garden area. Fertilizer can be broadcast before planting, or sidedressed around each plant, at a distance of 6 to 8 inches. Keep planted areas free from weeds, and use mulch to reduce weed germination and conserve soil moisture. Black plastic and organic mulches are equally effective. Water pumpkins regularly, and monitor them for insects or other pests.
Pumpkins are ready for harvest when their rinds have a hard, solid consistency and their color is a deep orange. Pumpkins should be left on the vine, if possible, until September or October, before significant frosting begins to occur. Pumpkins removed early will keep well in a cool, dry place, as long as they are harvested correctly. Cut pumpkins from vines with 3 to 4 inches of the stem attached, and avoid snapping them. Pumpkins without stems spoil faster than those that have been properly harvested. Harvest with a sharp pair of shears or a knife, and ensure the pumpkin is not sliced or bruised. Pumpkins keep best in dry air, between 50 and 55 degrees F.