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Growing the Perfect Pumpkin

I can almost see the head tilt: what? Pumpkins are a fall food/decoration and this is spring.

Pumpkins are native to the Americas. In fact, Native Americans cultivated pumpkins as an important food source. When half of the Pilgrims died after their first winter, the Patuxet Squanto Indians showed the survivors how to plant pumpkin vines in amongst the corn. One of the advantages of growing pumpkins was that they kept well throughout the winter, providing a continual source of fresh food.

Belonging to the family Curcubiaceace, there are four species: C. pepo, C. argyrosperma, C. moschata and C. maxima. The shape and coloration of pumpkins varies widely, but all are tendril-bearing vines with alternate leaves. Only C. pepo is considered a true pumpkin by botanists.

In the South, it is best to plant pumpkins of the C. moschata variety – these are the only ones that will tolerate the heat and humidity that is typical of our summers. Pumpkins in this variety have dark green, large, hairy, triangular leaves with pointy tips. The vines are spreading and the blossoms are large with leafy sepals at the base. The seeds are beige (smaller than most pumpkin varieties), and have an interesting “ragged” margin.

Miniature pumpkins are small enough to hold in your hand and are sold under cute names like ‘Baby Boo’, ‘Sweetie Pie’, ‘Jack Be Little’ and ‘Munchkin’. While the fruits are small, the vines spread rampantly so give plants lots of room (they are especially attractive grown on a trellis or arbor). All miniature pumpkins are C. pepo, so you may have mixed success growing them.

Culinary pumpkins are best when they have firm, sweet flesh. Recommended varieties include ‘Magdelena Big Cheese’, ‘Long Cheese’, ‘White Rind Sugar’, or ‘Golden Cushaw’.

Carving pumpkins are grown for their attractive appearance and generally are not good for eating. Selections that will do well in our summers are ‘Southern Field’, ‘Kentucky Field’, or ‘Dickinson’.

Pumpkins are grown from seed. When selecting seed, you will first determine the types of pumpkin you are interested in growing: miniature, culinary or carving. Other factors to consider are the number of days from sowing to harvest, the amount of space the vines will take, and whether or not the seed was open pollinated (pollinated by natural means). All heirloom varieties are open pollinated, and in general are hardier, more resistant to insects, and more flavorful.

Pumpkins are a long warm season crop (85-125 days from sowing to maturity) and should be planted as soon as the risk of frost is past; the last average frost date in Fairview is March 20. To germinate, the soil temperature must be over 60 degrees F. (the optimum range is 70-90 degrees F.) and the daytime temperature consistently between 80-85 degrees F. A good rule of thumb is to plant pumpkins when blackberries start to bloom. Plant in rich, well-drained soil in a sunny part of the garden, protected from wind (the large leaves dry out quickly).

Planting pumpkin seeds on hills allows you to incorporate lots of organic matter into the hill, and increases drainage. Space hills 8-10 feet apart (check the seed packet for the recommended spacing according to the variety you have chosen). In the center of each hill make a small depression and sow four evenly space seeds. Plant seeds 1-2” deep and lightly cover with soil. Most varieties germinate in 7-10 days. When the seedlings are 2” tall and have their first true leaves, remove all but the strongest by either pinching or snipping them off (don’t pull them out as you may hurt the roots of the remaining seedling). Seedlings will grow rapidly if provided with consistent moisture. An easy way to do this is to bury a plastic jug in the center of the hill (with holes punched in the bottom) and keep it filled with water. When using this system, plant the seeds around the jug.

Our springs are often cool and wet, so to get a jump on the weather, you can start seeds indoors two weeks before the last frost date. Timing is important because if the plants are held inside too long they will become spindly and root bound. Pumpkin roots grow long and thick and so quart or gallon size containers are best. The advantage of using pots made of peat or pressed fiber is that they can be planted directly into the garden and the risk of transplant shock is reduced. Fill containers with a sterile planting mix (or seed starting mix) within 1” of the top. Plant two seeds in each pot. Water the pot with a spray of warm water (if using tap water, allow it to sit out overnight so that chlorine and minerals will evaporate). Place the pot in a warm place (if you have a heat mat, this is the time to use it) and provide a light source for 12-18 hours a day. Water the pots daily so that the potting mix is moist but not soggy. Seeds should germinate in 5-10 days. In about two weeks the first true leaves should appear; at this time, thin to the strongest of the seedlings.

Harden off the seedlings by placing the pots outside in a protected, shady spot during the day and bring pots back inside before the sun goes down. After one week they can be left out overnight as long as the nighttime temperature doesn’t dip below 40 degrees F. Continue to check that the soil is consistently moist.

When planting into the garden, choose an overcast day or plant just before the sun goes down. Plant the seedling at the same depth it was growing in the pot. If more than 1” of stem shows above the ground, place soil around the stem to encourage root formation. If the seedlings are in pressed fiber or peat pots, poke some holes in the bottom and remove 1” of top. Any pot material that is exposed above ground will wick away moisture from the plant. Protect the seedlings from chilly nights by covering them with a floating row cover, or other product that can be removed during the day. An effective, low cost option is to cut out the bottom of a gallon jug and cover the plant. Whatever you use, make sure that the leaves don’t touch the sides of the plastic.

If you believe in the philosophy of companion planting (the close planting of different plants that enhance each other’s growth or protect each other from pests), don’t plant pumpkins near cucumbers (attract cucumber beetles which will attack the vines), potatoes (inhibit the growth of the vine and fruit), or raspberries (increase the susceptibility to blight). Good neighbors for pumpkins include borage and lemon balm (increases bee activity which increases pollination), corn and sunflowers (which act as windbreaks), nasturtiums (repel squash bugs), and radishes (deter cucumber beetles). It’s important to practice crop rotation by not planting pumpkins in the same place year after year.

Pumpkins are heavy feeders. Every three weeks during the growing season, side-dress with compost, fish emulsion, or a 5-10-5 fertilizer. Weeds compete with seedlings for water and nutrients, so keep the patch weeded (by hand so that roots are not disturbed). The best option is to apply a thick layer of mulch to discourage weeds, conserve soil moisture and keep fruits clean. Because pumpkins have hollow stems and large leaves, don’t allow the soil to dry out. Early morning watering is best so that the leaves have a chance to dry out before the sun goes down.

To encourage a nice, round shape, rotate the fruits occasionally, but turn just a little each time so that the brittle stem is not broken. During the two weeks before the anticipated harvest date, pinch out flowers and small green fruits so that the energy of the plant can be directed to the remaining pumpkins.

Harvest pumpkins as they reach the size that you desire. A good indication that the pumpkins have reached their mature size is that the vines and leaves turn brown and shrivel, the fruit turns from yellow to orange, and the rind hardens (stiff enough that your fingernail won’t pierce the skin). Use shears to cut the stems as long as possible (6” is perfect). Do not pick up a pumpkin by its stem; if it breaks the fruit will rot. All pumpkins must be harvested before the first fall frost (the average first fall frost date in Fairview is November 12) or the fruits will be ruined for storage.

Pumpkins need to be cured before they are stored. This process hardens the shell and reduces the water content, making the flesh sweeter. Cure pumpkins by laying them in a single layer, without touching, in a warm (70-80 degree F.) place for at least a week. After curing, wipe the shells with a damp cloth dipped in a 1:10 bleach:water solution. They are now ready to be stored.

Late-maturing and hard shell varieties store best. Store whole pumpkins with stems at least 2” long and skin so hard that your fingernail won’t pierce the skin. A whole pumpkin will store at room temperature for one month and five months in the refrigerator. Pumpkins can also be frozen, canned or dried.

One of the biggest challenges you’ll face when growing pumpkins is the stress that occurs when our daytime temperatures exceed 90 degrees F. and nighttime temperatures stay above 80 degrees F. Working a lot of compost into the soil before planting will provide good moisture retention in the soil and lessen the stress. Using a fertilizer with a high phosphorous content (the middle number of the N-P-K formula), will encourage the growth of a large root structure and allow the plant to uptake water and reduce stress as well. Mulch will help keep the soil cooler and help retain moisture.

Throughout the growing season, train vines to grow away from the shoulders of the fruit to avoid twisting the vine or crushing a runner. Most pumpkin growers recommend pruning the vines when the plant reaches a size of 20 feet in diameter (usually in late summer). At this time, start removing the tips of the runners and remove any side runners before they set down roots. Continue this practice until harvest.

Pumpkins take up a lot of space in the garden, so give them lots of room to roam. Placing plants closer than recommended will result in smaller fruit and increased pest/disease problems. Options to allowing vines to roam are to trellis them (larger fruits will need to be hung in slings - a good use for the pantyhose that we rarely wear these days), pinch back the growing tips after the fruits have set, or choose a compact variety.

There are several pests that attack pumpkins: aphids, cucumber beetles, squash bugs, leaf miners, leaf hoppers, white flies and squash vine borers. If you know the life cycle of the pests, you can use floating row cover at the time of their emergence. Be alert to egg clusters on the underside of leaves and remove the individual leaves (place in a plastic bag in the trash, not in the compost pile). If you find that your plant is infested, go on attack immediately. The first line of defense is a sharp blast of water, hand-picking the bugs and drowning them in a jar of water, or using a product such as Safer soap. If you must resort to a stronger chemical, read and follow the label directions.

There are several diseases that attack pumpkins: blights and wilts, anthracnose, rots and mildews, and viral diseases. Most can be avoided by planting resistant varieties or controlled with the use of fungicides; the exception is viral diseases, the plant must be removed and destroyed (once again, not in the compost pile).

While it may seem like a lot of work to grow pumpkins, they are really quite easy, fun and rewarding to grow. I hope you’ll give it a try and have your own pumpkin patch this year.

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