All about Pumpkins

October is pumpkin season!  Whether its pumpkin pie or pumpkin spiced lattes, cute décor or scary jack-o-lanterns, many of us enjoy pumpkins this time of year. 

Below are answers to common pumpkin questions.

What is a pumpkin?

This is a more difficult question to answer than you would suspect! “Pumpkin” is a general term used to describe any winter squash that has a hard rind, typically ribbed, and roughly round in shape with orange to yellow (sometimes white) skin. There are several species and varieties of squash that fit this description.  That means the common name of pumpkin is used for several different species of squash. Cucurbita pepo includes field pumpkins (pumpkins that we associate with jack-o-lanterns and Halloween) and acorn squash. Cucurbita moschata includes butternut squash and a few other pumpkins (‘Dickinson’ is a popular one). Cucurbita maxima are the large-fruited squash like Hubbard squash and pumpkins like ‘Big Max’ or ‘Dill’s Atlantic Giant’ (these are the super-sized pumpkins you see at the state fair). The final species is Cucurbita mixta which includes cushaw-type pumpkins.

How do you pick the perfect pumpkin?

When at the store or pumpkin patch look to purchase pumpkins that are firm, heavy, and uniform in color.  Avoid fruit with any cuts, holes, bruises, or soft spots on the outer surface.  Wash or brush any dirt off the pumpkin to be sure there are no damaged spots on the rind.  The rind should not feel spongy and pumpkins should have a deep hollow sound when knocked on with your hand.  Unless it is being used for cooking, be sure it sits nicely and won’t wobble or fall over while on display.  Look for pumpkins with a stem still firmly attached to the fruit. Not only are they more attractive, but they are less likely to rot with a stem intact.   Transport pumpkins in boxes or areas of the vehicle where they will not roll around in transit as this can cause cuts, bruises, or stems to be broken off.  Do not carry the fruit by their stems as it may not be able to support the weight of the fruit and may break off.  Once home, wash the outside of the pumpkin with soapy water or a solution of 10% bleach solution (1 part bleach to 9 parts water) to remove any fungus or bacteria that may cause rot.  When stored in a cool, dry location that will not freeze, pumpkins can be enjoyed for several months.

How do you grow pumpkins?

Pumpkins perform best in fertile, well-drained soils containing high levels of organic matter. They also require full sun. Organic matter levels can be increased by incorporating well-rotted manure or compost into the soil.  In average garden soils, apply and incorporate 1 to 2 pounds of an all-purpose garden fertilizer, such as 10-10-10, per 100 square feet prior to planting.

Pumpkins are commonly planted in hills spaced 4 to 5 feet apart with 5 to 7 feet between rows. Sow 4 to 5 seeds per hill at a depth of 1 inch in mid-May in central Iowa. Thin to 2 to 3 vigorous, well-spaced plants per hill when seedlings have 1 or 2 true leaves. The last practical planting date in Iowa is mid-June.

For an early crop, start plants indoors 3 to 4 weeks prior to the anticipated outdoor planting date. Since the seedlings don't tolerate root disturbances during transplanting, start seeds in peat pots, peat pellets (Jiffy 7's), or other plantable containers. Sow 3 to 4 seeds per container. Later, remove all but 2 seedlings. Harden the plants outdoors for a few days in a protected location prior to planting to lessen transplant stress.

Control weeds with frequent, shallow cultivation and hand pulling. Water plants once a week during dry weather.


October is pumpkin season! Photo courtesy of Cindy Haynes. 

What common pests and diseases affect pumpkins?

Pumpkins, along with many other winter squash, are susceptible to several insect pests and diseases.  Squash bugs, squash vine borers, and powdery mildew are serious and common problems encountered when growing pumpkins at home.

Squash bugs have piercing-sucking mouthparts. Heavy feeding causes entire leaves to wilt, turn brown, and die. Several methods can be used to control squash bugs in the garden. Adults and brick red egg masses on the undersides of leaves can be removed by hand. Adults can also be trapped under boards or shingles placed under the plants. Turn the objects over daily and collect and destroy the hiding squash bugs. Small, immature squash bugs (nymphs) can be controlled with insecticides, such as carbaryl (Sevin). In fall, remove and destroy plant debris to deprive squash bugs of overwintering sites.

Squash vine borer larvae bore into squash stems near ground level. Larvae feeding within the vines eventually causes the plants to wilt and die. Squash vine borers can be controlled with applications of insecticides (rotenone, permethrin, or malathion) at regular intervals beginning in mid-June. Apply the insecticide to the base of the vines. After the final harvest, remove and destroy the plant debris. Rototilling in fall or spring may destroy overwintering pupae in the soil.

Powdery mildew is white spots or “powder” that develops on leaves starting in mid-summer and enlarge as the summer progresses. By late summer or fall entire leaves may appear white. Powdery mildew is usually favored by moderate temperatures and humid (but not wet) conditions. It tends to be more severe in the shade and in areas with little airflow. Because of this, putting plants in full sun and cultural practices that promote airflow (such as appropriate spacing) can help to minimize powdery mildew problems. Avoid overhead watering to keep foliage dry. Fungicides can be used if powdery mildew infestations have caused yield losses in the past.  Inspect foliage frequently in early summer and at first sign of the disease apply sulfur-based fungicides according to label directions.  Reapplication will be necessary for the remainder of the growing season to prevent the disease from spreading.

How do you harvest and store pumpkins?

Harvest pumpkins when they have developed a uniform orange color and have a hard rind.  Harvest all mature pumpkins before a hard freeze.  A light frost will destroy the vines but should not harm the fruit.  However, a hard freeze may damage the fruit.

When harvesting pumpkins, handle them carefully to avoid cuts and bruises.  These injuries are not only unsightly, they provide entrances for various rot-producing organisms.  Cut off the fruit with a pruning or lopping shears.  Leave a 3- to 4-inch handle on the pumpkins.  A pumpkin with a 3-to 4-inch handle is more attractive.  Also, pumpkins are less likely to rot when they are harvested with a portion of the stem attached to the fruit.  Do not carry the fruit by their stems or handles.  The stems may not be able to support the weight of the fruit and they may break off.

After harvesting, cure the pumpkins at a temperature of 80 to 85 degrees Fahrenheit and a relative humidity of 80 to 85 percent.  Curing helps to harden their skins and heal any cuts and scratches.

After curing, store pumpkins in a cool, dry, well-ventilated location.  Proper curing and storage slows the rate of respiration and prolongs the storage life of the fruit.  Storage temperatures should be 50 to 55°F.  Do not store pumpkins near apples, pears, or other ripening fruit.  Ripening fruit release ethylene gas which shortens the storage life of pumpkins.  Place the pumpkins in a single layer where they don't touch one another.  Good air circulation helps to prevent moisture from forming on the surfaces of the fruit and retards the growth of decay fungi and bacteria.  Placing pumpkins in piles generates unwanted heat which may result in the rotting of some fruit.  Periodically check pumpkins in storage and discard any fruit which show signs of decay.  Properly cured and stored pumpkins should remain in good condition for 2 to 3 months.

What type of pumpkin is made into canned pumpkin? 

Generally little pumpkin is used for canned pumpkin puree – at least very little of the species and varieties we think of when we think of pumpkins!  Instead most canned pumpkin is actually made from butternut or other winter squashes. The term “pumpkin” is used to describe many different species of squash and the most edible species is used for canned pumpkin puree.  The primary squash/pumpkin used for pumpkin puree is a type of Cucurbita moschata which includes butternut squash and Dickinson pumpkin, the most common commercially grown cultivar. While Curcurbita pepo, the species that grows pumpkins used for jack-o-lanterns, is the species most commonly associated with the name pumpkin (and it is edible), it is not used for canned pumpkin puree because it tends to be more fibrous or stringy.

What is pumpkin spice?  

Pumpkin spice describes a popular spice blend that is typically used to flavor pumpkin pie.  It is a combination of cinnamon, cloves, ginger, nutmeg, and allspice.  While most bakers have a special and sometimes secret recipe for this spice blend, it is usually 4 parts cinnamon to 1 part ginger, nutmeg, allspice, and cloves respectively.  Interestingly, while pumpkins are native to temperate North America, all of the spices used in pumpkin spice blends are from tropical plants.

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Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on October 15, 2021. The information contained within may not be the most current and accurate depending on when it is accessed.