Squash belongs to the genus Cucurbita, a group of plants within the gourd family, Cucurbitaceae. Although botanically fruits, they are typically treated as vegetables in a culinary context. Squash has a deep history in global agriculture, with evidence of domestication in Mesoamerica dating back at least 8,000 years, predating the cultivation of both maize and beans in the region.
The Complexity of Counting Squash Varieties
Determining a single, definitive number for squash varieties is impossible due to botanical classification and ongoing cultivation. The Cucurbita genus includes approximately 13 to 30 species, but only a small handful are widely grown for human consumption. The complexity lies in distinguishing between a species and a cultivar.
A species is a basic biological unit, while a cultivar (cultivated variety) is a population selected by humans for specific traits. While the number of recognized species is low, the number of cultivars derived from them is vast. Globally, the number of distinct, named cultivars and hybrids is estimated to run into the hundreds, potentially exceeding 400 varieties. This number constantly changes as new varieties are bred and older ones disappear.
Distinguishing Summer and Winter Squash
Squash is commonly categorized by the culinary distinction of summer versus winter squash, based on their maturity at harvest and physical properties. Summer squash is harvested when the fruits are young and immature, typically during warmer months. These varieties are characterized by a tender, thin, edible skin and soft flesh with high water content.
Summer squash, such as zucchini and pattypan, have a short shelf life due to their delicate nature. Their seeds are immature and soft, making the entire fruit suitable for consumption without extensive preparation. Summer squash is best suited for quick cooking methods like sautéing, grilling, or eating raw.
Winter squash is left on the vine until full maturity, usually harvested in late fall before the first frost. This longer period allows the rind to harden and thicken significantly. This tough exterior enables varieties like butternut and acorn to be stored for months throughout the winter. The mature flesh is denser, less watery, and often sweeter than summer varieties, making it ideal for roasting, baking, or pureeing.
The Four Major Edible Squash Species
The immense diversity of squash, from zucchini to massive pumpkins, originates primarily from just four domesticated species of the Cucurbita genus. Understanding these species provides the biological structure for culinary classifications.
Cucurbita pepo
Cucurbita pepo is the most diversified species, containing the largest range of forms and the majority of summer squash varieties. This species includes summer staples like zucchini and yellow crookneck squash, as well as winter varieties such as acorn, delicata, and spaghetti squash. C. pepo is known for its hard, angled peduncle (stem).
Cucurbita maxima
Cucurbita maxima is responsible for the largest squash and pumpkin varieties. It is characterized by a softer, spongy peduncle that flares out at the point of attachment. This group includes the Hubbard squash, turban squash, and the dense-fleshed Kabocha. C. maxima varieties are recognized for their sweet, starchy flesh.
Cucurbita moschata
Cucurbita moschata varieties are notable for their high beta-carotene content, which contributes to their deep orange flesh. This species is identified by a hard, woody, five-sided peduncle that is distinctly flared where it meets the fruit. The most recognizable member of this group is the butternut squash, along with the Long Island Cheese and Seminole pumpkins.
Cucurbita argyrosperma
Cucurbita argyrosperma (formerly C. mixta) is the fourth major species, though it is less common in mainstream markets. The most well-known cultivar is the cushaw squash, which has a distinct bell or pear shape. This species is primarily cultivated in Mexico and the southwestern United States.
A Guide to Common Market Squash
Many frequently purchased squash varieties belong to the dominant Cucurbita pepo species. Zucchini, the common green or yellow cylindrical squash, and Pattypan squash, with its distinctive flat, scalloped shape, are both summer squash cultivars of C. pepo.
Acorn squash, known for its dark green, deeply ridged rind, and Spaghetti squash, which produces stringy, noodle-like flesh when cooked, are winter varieties belonging to C. pepo. Butternut squash, a tan-skinned, bell-shaped winter squash, is a prime example of C. moschata. Kabocha squash, prized for its sweet, dry texture, is a winter squash belonging to the C. maxima species.