How to grow a monster pumpkin

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Giant pumpkin. Photo: Lynn Ketchum
Last Updated: 
June 29, 2006

EUGENE - Is this your year to grow a giant pumpkin? If so, late May into June is the right time to get started.

To grow a giant pumpkin, you'll need about three to four months of warm growing days with daytime temperatures above 75 degrees.

Purchase seed from a pumpkin variety with the potential to grow to a large size. A couple of the largest varieties that are recommended by the OSU Extension Service as performing well under Oregon conditions include: Dill's Atlantic Giant - Bred in Nova Scotia for its gargantuan size, this variety has been known to surpass 990 pounds, with the proper growing conditions. Prizewinner - This variety regularly tops 200 pounds, says Nichol's seed catalog.

Both varieties are available from the following Oregon seed companies: Nichol's Garden Nursery, 1190 North Pacific Hwy., Albany, OR 97321-4580 or The Territorial Seed Company, P.O. Box 158, Cottage Grove, OR 97424-0061.

Plant your pumpkin seeds after the danger of frost has passed and the soil is thoroughly warm. Or start your seeds indoors and transplant outside when the soil warms up above 55 degrees. Check on the seed packet the number of days recommended for the pumpkin to grow big.

Pumpkins love fertile soil. Before planting, spade the soil about a foot deep and mix in some compost, manure, or well-balanced fertilizer. Then plant two or three seeds in a group about an inch apart in moist soil. Cover the seeds with a half-inch inch of moist soil and firm it lightly over them, then place another half-inch of soil loosely on top. Keep the soil moist, but not wet. Too much water will slow plant growth and encourage fungus diseases.

Here are some hints for encouraging your pumpkin to grow to the maximum size possible, from Ross Penhallegon and Pat Patterson, horticulturists with the Oregon State University Extension Service:

  • With cooler nights in the western regions of the state, give your pumpkin plants as much heat as possible by planting seeds under a cloche or hot cap, mulching with black plastic, or covering the growing vine with spun fiber row cover, especially as weather gets cool again in the early fall.
  • Once your pumpkin seedlings have three leaves, remove all but the strongest plant.
  • When a plant forms runners, give them more fertilizer. Ammonium sulfate or other source of nitrogen such as rotted manure, fish, or blood meal is best. Rake it in lightly, then water thoroughly.
  • Remove moisture and nutrient-robbing weeds.
  • Once three fruits set, pinch back the vines to encourage further development of the fruit. Any additional blooms should be picked. When the three baby pumpkins are about 6 inches in diameter, select the best-shaped one and pick the other two. All of the vine's food will now go to feed your potential giant.
  • Gently roll the pumpkin every week or so throughout the growing season for a perfect shaped pumpkin. You may want to place the growing pumpkin on a large piece of cardboard or piece of wood to repel soil insects. Protect the pumpkin from aphids, mites, whiteflies, leafhoppers, and squash bugs. Since early pest detection and treatment result in better control, inspect your plants frequently.
  • Fertilize your single pumpkin every two weeks or so with decomposed manure, compost or other source of nitrogen. Always water it well.
  • Harvest before the first frost. Cut your orange monster off the vine with a sharp knife, when the stem becomes hard and woody, usually about three months after planting. In most places in the state, fall frosts can begin in September. If an early frost is predicted, use a row cover to protect the wine and pumpkin. Leave two inches of stem - a broken or missing stemmed pumpkin keeps poorly.
Author: Carol Savonen, Pat Patterson