Pumpkin (Curbita spp.) is an iconic plant in North American gardens, a form of squash that symbolizes autumn through its use in creative Halloween jack-o-lantern carvings or as a filling for delicious Thanksgiving pies. While most people think of a pumpkin as a large, spherical orange fruit with a ribbed rind, pumpkins also come in colors including white, red, pink, and blue, and with rinds that can be smooth, bumpy, oval, flattened, or round.
All pumpkins are a type of winter squash, but some are simply grown as decoration. Most home-grown pumpkins are cultivar or hybrids of the Curbita pepo species, but there are also other pumpkin species you may run across, including C. maxima, C. argyrosprema, and C.moschata. The species readily cross-pollinate and many commercial varieties are carefully developed hybrid types.
Like most squash, pumpkin is a low-growing vining annual with large, coarse leaves. The plants flower with yellow blooms in July and August, producing rapidly growing fruits that are left to ripen on the vine for harvest in fall.
Pumpkins require quite a long period of frost-free weather (75 to 120 days) to mature, and they also require warm soil temperatures (at least 60 degrees Fahrenheit) for the seeds to germinate. For this reason, they are typically seeded into the garden just as soon as the soil is sufficiently warm in the spring. In regions without the necessary long growing season, pumpkins are often started from seeds indoors, two to four weeks before the last spring frost.
|Botanical Name||Curbita spp., especially C. pepo|
|Plant Type||Annual vine|
|Size||9 to 18 in. tall; 10- to 15-foot spread|
|Sun Exposure||Full sun|
|Soil||Rich, moist, loamy|
|Soil pH||Slightly acidic (6.0 to 6.8)|
|Native Area||North America|
|Hardiness Zones||Grown as an annual in zones 2 to 11|
How to Plant Pumpkins
Pumpkins are typically planted in raised rows or in hills that allow the sun to warm the soil early in the spring. Plant four or five seeds per hill, about 1 inch deep. Hills should be spaced 4 to 8 feet apart, as these plants require a lot of space to sprawl out. Where space is limited, pumpkins can be trained up a trellis; make sure it is strong and study since there can be as many as nine pumpkins per vine. When the plants are 2 to 3 inches tall, thin out the seedlings to retain one or two of the most vigorous plants.
Growing pumpkins is mostly about giving them plenty of food and water, as both are essential for growing large fruit. Be very careful of the vines as the plants grow, as they are surprisingly delicate. As the pumpkin fruit begins to form at the base of the flowers, snip off all but a few of the developing fruits in order to direct energy to the remaining pumpkins. This is especially useful if your goal is to grow large jack-o-lantern pumpkins. A piece of cardboard or a wooden board placed under the fruit will prevent it from rotting.
Turn the pumpkins slightly every week or so, to keep the growth symmetrical. Do this gently—you don’t want to snap the vines.
Pumpkins (and all squash) need full sun to produce and mature their fruits.
Pumpkins prefer rich, well-draining soil. Before planting, mixing in a good amount of organic material, such as compost or peat moss, is recommended. Soil pH should be slightly acidic, 6.0 to 6.8.
Give your plants at least 1 to 2 inches of water a week, especially when they're blooming and setting fruit. Watering should preferably be done through drip irrigation or ground-level soaking rather than from overhead.
Temperature and Humidity
Like all squash, pumpkins need heat—and lots of it—to produce good fruit. Pumpkins grow best at temperatures between 65 and 95 degrees Fahrenheit. Very humid conditions, when combined with heat, can foster the growth of fungal diseases.
Pumpkins feed heavily in order to develop their extensive vines and large fruit. Feed regularly (every two weeks), beginning with a high-nitrogen fertilizer when the plants are about 1 foot tall, to support good foliage growth. Just before the plants begin blooming, switch to a high-phosphorus fertilizer to support fruit development.
The best pumpkin varieties to grow will depend on how you plan to use them.
Some pumpkin varieties good for cooking include:
- 'Cinderella' is so named because it looks like the deep-ribbed pumpkin that transformed into Cinderella's coach in the classic animated movie. It has thick, custard-like meat that works well in all types of cooking.
- 'Lumina' is a white pumpkin that works well for baking, with a rind that also is good for carving.
- 'Sugar Pie' is excellent for pies since it has sweet, fine-grained flesh. You also can use this variety in soups and casseroles.
Pumpkins good for carving include:
- 'Connecticut Field' is the variety most often grown commercially for Halloween use. This standard orange pumpkin weighs between 10 and 20 pounds. It is not a great pie pumpkin, but it makes a great Jack-o-lantern, with an easy-to-carve rind.
- 'Jack-O-Lantern', aptly named, has a relatively thin rind that glows when a light source is placed inside the hollowed shell.
- 'Howden' is a slightly elongated pumpkin weighing up to 20 pounds. Its meat is also good for cooking.
Unusual, novelty pumpkins are now available in dozens of varieties, including:
- 'Atlantic Giant' is a variety for those who want to try their hand at growing mammoth pumpkins. Individual pumpkins have known to exceed 1,000 pounds.
- 'Wee-Be-Little' is a miniature, baseball-sized pumpkin that grows on bush-like vines.
- 'One-Too-Many' is named because the creamy skin with red veins is said to resemble the complexion of a drunken person. It makes a good pie pumpkin, and can also be used for carving or decoration.
- 'Red Warty Thing' is a bright orange-red pumpkin covered with knobby "warts." It is great for carving and also can be used in cooking.
Pumpkins are long-season growers. Most need somewhere between 90 and 110 days to mature. If you live in a short-season climate, make sure you choose a variety that will have time to mature in your garden.
Don't rush harvesting, or your pumpkins won't last long or taste great. Wait until the color is uniform and the shell doesn’t dent when pressed with a fingernail. At this point, the vines should have begun to dry and shrivel. Watch for when the tendril closest to the pumpkin turns brown. That's the peak time to harvest.
Pumpkins can withstand a light frost but always harvest before a hard frost. Cut them off the vines with a pruner, leaving 2 to 4 inches of stem. This is not a handle—it's there to help the pumpkin cure and to keep a disease from entering where the stem joins the pumpkin. Try not to break it off.
Pumpkins are quite the same as true winter squashes. They will not store through the winter, but you should be able to hold onto them for a month or two. They need to be cured to store well. Place in a warm, sunny spot (low to mid 80s degrees Fahrenheit) and space them far enough apart so they are not touching. Allow them to cure about 10 days. Then, they can be stored in a cool, dry spot (50 degrees).
Common Pests and Diseases
Pumpkins are prone to many of the pests and diseases that affect other types of squash. Most damaging are vine borer insects that can infiltrate the stems and kill the plants. Vine borers are hard to treat, so the best approach is prevention—wrapping the base of the vine where it meets the soil with tin foil or another shielding material.
Squash bugs and cucumber beetles can also be a problem with pumpkins. Squash bugs most often affect young plants, causing them to wilt and die. The best preventive measure is to regularly inspect plants and pick off the red eggs or grayish insects. A variety of pesticides approved for pumpkins will kill these insects, but chemical controls should be a last resort.
Cucumber beetles are small striped beetles that eat holes in leaves and cause them to turn yellow and wilt. You can prevent cucumber beetles by using row covers over the plants, but these will need to be removed when it is time for the flowers to pollinate.
Powdery mildew is the most common disease of pumpkins. It is caused by fungal spores in the soil splashing up onto the leaves. It is very hard to prevent or treat, though there are mildew-resistant varieties you can grow. Fortunately, powdery mildew is rarely fatal—just somewhat unsightly.
Pumpkins can also fall prey to anthracnose—a more serious fungal disease. Anthracnose causes dark, sunken lesions on leaves and can also affect fruits that lie on the ground. It thrives in wet, warm conditions and is spread by rainfall or by watering. Remove and destroy any damaged plant parts as you spot them, and keep the ground free of debris. Once anthracnose is widely present in the soil, you should rotate crops for the next season. Don't plant any pumpkins or Curbita species in that area for two or three years.