Is a Pumpkin a Squash? Understanding Cucurbitas

Learn the difference between Cucurbita pepo and Cucurbita maxima squash – and where “pumpkins” fit into the family.

| Fall 2016

It’s somewhat difficult to come up with a backyard garden crop more a part of American culture than that plump, round, ribbed, vining fruit that we look forward to honoring every fall. Of course, corn makes the world go ‘round — but not sweet corn like you find in the typical backyard garden. Americans also consume about a potato per day on average. And who doesn’t like green beans? Yet all those backyard crops take a back seat each fall as families head into the pumpkin patch, gather around the picnic table to carve jack-o’-lanterns, and in the end enjoy a delicious squash pie at Thanksgiving. Wait … squash?

The simplest maxim is all pumpkins are squash, but not all squash are pumpkins. So what is a pumpkin, and why do we care? Botanists call one particular group of squash, which belongs to one particular species, pumpkins. The species, Cucurbita pepo, differs from all other species of squash in certain characteristics, such as its leaves and stem. The classic orange fruit, whether big or small, round or oblong, is what botanists routinely agree is a pumpkin. Not everyone else, though, is on the same page. Let’s try to get to the bottom of it, shall we?

C. pepo squash include scallop (var. clypeata), zucchini (var. cylindrica), yellow summer squash, the winter varieties of acorn (var. turbinata), pumpkin (var. pepo), and spaghetti squash, among others. One difference between summer and winter squash is that we eat summer squash before the seeds have hardened and the fruit has ripened, while we eat winter squash only after the fruit has matured.

The Domestication of Cucurbita Pepo

Let’s wind back thousands of years. Some 8,000 to 10,000 years ago, Native Americans domesticated C. pepo squash from wild gourds in Mexico. What these squash were really like is unclear, but they may have been cultivated only for their seeds at first and, in some cases, for their hard shells. What we do know is that these first domesticated fruits contained the distinctive orange pigmentation of true pumpkins.

Fast forward four or five thousand years to eastern North America, where a second group of Native Americans domesticated another gourd — the Ozark wild gourd (C. pepo var. ozarkana) — and created a whole new line of C. pepo squash cultivars, possessing green, white, and yellow skin colors and a vast array of fruit types. These all had, and still have, the ability to cross-pollinate with each other. Cucurbita pepo is one of the most variable species in the world for fruit shape. If you let your zucchini cross-pollinate with your acorn squash and grow out the seeds, you’ll see what I mean.

By the time Columbus came to America, Native American agriculture was in full swing, including the extensive cultivation of corn, beans, squash, sunflowers, and Jerusalem artichokes in the eastern section of the continent. The squash species in the northeast was primarily C. pepo, with some cultivation of Cucurbita argyrosperma in the more southwestern reaches of eastern America. The C. pepos had a wide array of fruit types, including what we typically call gourds, similar to the types grown for Halloween today. There were also types of scallop summer squash, acorn winter squash, and our familiar orange pumpkin.

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