It’s Pumpkin Season!
How to Grow Our Favorite Fall Food

By Kari Spencer

At the close of a long hot summer, the arrival of the pumpkin heralds the welcome arrival of autumn.  More than just the emblem of ancient folklore, the pumpkin packs a nutritional punch, supplying a rich source of vitamin C, vitamin A, fiber, and potassium. The kings of the fall garden, pumpkins demand a large amount of real estate in which to grow, generous quantities of water, fertile compost-enriched soil, and ample sunlight. In exchange, the gardener is rewarded with a harvest of pumpkins that are nutritious, delicious, and versatile for many kinds of recipes.
When to Plant:  Pumpkin seeds will not germinate in cold soil and tender seedlings are easily damaged by frost, so it is best to refrain from planting until all danger of frost has passed. In cool climates, it may be helpful to warm the soil one week before planting by covering it with black plastic. To plant, cut one-inch holes in the material and plant through the openings. In northern regions of the United States, plantings are generally made in late May, or in early July for southern regions.
How to Plant:  Enrich the garden soil with generous amounts of compost or composted manure.  Plant pumpkin seeds one inch deep in mounds or rows spaced 3-5 feet apart, depending on the variety.  To ensure good germination rates, place four or five seeds per hill, thinning to one or two healthy seedlings per hill as they begin to grow and develop several leaves.
Locate plants near the edges of the garden so that the aggressive vines can be directed away from other plants. As pumpkins begin to develop, support them on a thick piece of newspaper, a carpet square or cardboard to discourage rot that occurs when the tender skin comes in contact with the soil underneath.
Watering:  A regular, deep watering schedule will help pumpkins to grow large in size, at an even growth rate that prevents splitting.   Water the soil around the plant stem using a drip system or soaker hose, and avoid wetting the leaves and fruits, which can encourage the development of fungal diseases.  The ideal time of day to water is early in the morning.  During the afternoon heat, pumpkin leaves will often wilt, and then perk up again as the sun begins to set.  However, if you notice wilting before noon, it may be a sign that the plant needs more water.
Fertilizing:  Amend the soil regularly with a layer of compost or composted manure that is spread on top of the soil or piled in trenches between planting mounds. Begin to fertilize when plants are about one foot tall with a nitrogen fertilizer that will promote healthy vines and leaves. Watch closely for signs that flowers are beginning to form.  Then, to encourage blooms, switch over to a product that has less nitrogen and more phosphorous, such as a “bloom booster” fertilizer.  Too much nitrogen at the bloom stage can cause vines to continue to grow leaves at the expense of flowers, which will result in a diminished harvest.
Increasing Pumpkin Size:  To increase the size of your pumpkins, pinch off the fuzzy ends of the vines when they begin to set fruits.   This will halt lateral vine growth and focus the plant’s energy on producing large-sized pumpkins.  Maximizing the size of giant varieties is accomplished by removing all but one or two female flowers from each vine.  By doing so, all of the vine’s energy is concentrated on growing one or two mammoth-sized pumpkins.
Weeds:  Pumpkins do not thrive if they have to compete with weeds for water and nutrients.  Keep the rows and mounds free of weeds, but be mindful of aggressive cultivation.  Pumpkins have shallow roots that are easily damaged by garden tools.
Troubleshooting:  A common complaint amongst gardeners is that their pumpkins have blooms, but are not setting fruit. It is helpful to know that the first flowers that appear on pumpkin vines are all male.  If the vine has just begun to show flowers, all that may be necessary is a little bit of patience until the female blooms appear, and then fruit will begin to set.  If female blooms are present, but pollination is not occurring, check the weather.  Daytime temperatures hovering over 90^oF, with night time temperatures in the 70s or above, hinder pollination.  Fruit set should resume as temperatures drop.
Pests:  Pumpkin pests include cucumber beetles, squash bugs, squash vine borers, corn rootworm beetles and aphids.  Monitor your plants daily to catch infestations in their early development, deterring the insects with a spray of neem oil, pyrethrum, or other organic treatments. Applications should be made at dusk to reduce damage to beneficial insects.  Remove infested plant materials and debris from the garden, and dust the soil with diatomaceous earth to hinder tender larvae.
Diseases:  Powdery mildew is a fungus that shows up as gray or white spots on leaves and stems.  It is an incurable condition, weakening plants and distorting fruits if not controlled.  To curb its negative effects, remove diseased plant material and discard it in a hot compost pile or bag it and throw it away.  Spray the remaining plant with a mixture of one part cow’s milk to nine parts water, or one teaspoon baking soda to one quart of water.  Either of these mixtures will help to prevent the spread of the disease, and both treatments must be reapplied after rain.
Harvesting:  Pick pumpkins when the flesh is a deep, solid color.  The rind should be hard and the skin resistant to light pressure by your fingernail.  The best time to harvest is in late September or early October. Use gloves and pruning shears to remove the pumpkin from the vine, leaving a few inches of stem attached.  Pumpkins with intact stems not only have a handle, but they also remain fresh longer.  Use caution when handling pumpkins as wounds and bruises decrease the amount of time that they will “keep.”
Curing: Cured pumpkins taste best and last longer.  To cure harvested pumpkins and harden the rind for storage, set them in the sun for ten days.  Cover or move them into a shed if rain or frost is predicted.  When cured, store pumpkins in a cool place (ideally 50^oF,) protected from frost, with none touching another.  Pumpkins kept in ideal conditions should last two to three months without spoilage.
Once carved for Jack-O-Lanterns, pumpkins can rot quickly.  Make your carved creations last longer by submerging them in a bucket with a ten-percent bleach solution (one part bleach and ten parts water.)  After soaking for ten minutes, remove them from the water and allow them to dry.  The bleach will deter decomposing bacteria so that your pumpkin stays fresh.  If you notice a black spot growing on the interior, soak the pumpkin again or cut out the spot and spritz the area with bleach solution. Display pumpkins in a cool area out of the sun to ensure that they look lively throughout the season.
Kari Spencer is a Master Gardener volunteer and the founder of The Micro Farm Project, a tiny urban farm in the heart of Phoenix, AZ.  A former elementary school teacher, she currently enjoys teaching adults, spreading her passion for gardening, cooking and small livestock.  She shares the farm with her husband, Lewis, their four daughters, and a host of chickens, turkeys, sheep, goats, rabbits and quail. Check out her blog!