Cucurbita pepo L.

Standardized Common Name: Pumpkin

Family: Cucurbitaceae

Taxonomy: The term “pumpkin” has no taxonomic meaning, and is at least occasionally applied to large, thick-rinded fruits belonging to four species, including C. argyrosperma Huber subsp. argyrosperma (also known as C. mixta Pang.), C. maxima Duch., and C. moschata Poir. as well as C. pepo. Cucurbita pepo subsp. pepo, the most common of the cultivated species, encompasses a wide variety of fruits, including zucchini and summer and winter squash varieties as well as many pumpkins. The thin-hulled Styrian Oil Pumpkin, C. pepo subsp. pepo var. styriaca Grebenščikov, is commonly used in the production of pumpkin oil.

Description: Annual vine, prickly-stemmed, with twining tendrils at the base of some leaves. Leaves alternate, long-petioled, erect, to 30 cm long and broad, palmately lobed, prickly; base cordate; apex and apices of main lobes broadly acute; margins wavy or toothed. Plants monoecious. Flowers unisexual, solitary in leaf axils, long-pedicelled; calyx cup-shaped, bristly, green, 5-lobed; corolla funnel-shaped with 5 erect to spreading lobes, yellow, to 10 cm long. Male flowers with 3 stamens; filaments white, short, free below and fused above; anthers forming a central column, 1–1.5 cm long, yellow, with convoluted surface. Ovary of female flower inferior, 3–5-loculed; styles fused into short column; stigmas 3, yellow, convoluted. Fruit a pepo, with leathery exocarp and thick fleshy edible mesocarp; size and shape extremely variable, the largest exceeding 100 kg in mass; color variable, ranging from green and white to bright orange at maturity; peduncle in fruit strongly 5-angled; seeds numerous, to 2.5 cm long, ovate, flattened, pale.

Parts in Commerce: Seeds

Identification: Most varieties of C. pepo are thick-hulled, which is the primitive condition.

• (10–)15–25 mm long, 7–14 mm broad
• Strongly flattened
• Ovate with a narrowed neck, the neck often curved to one side
• Conspicuous smooth, rounded margin around edges; groove or ridge delimiting margin visible on each side of seed
• Groove may be brownish-tinged, but margin itself not darker than face of seed
• Scar at end of neck perpendicular to neck, slightly angled, or rounded
• Surface cream to tan throughout, smooth or with irregular wrinkles
• Seed coat easily broken; interior of seed taken up by whitish embryo surrounded by thin green layer
• Embryo edible, with mild, nutlike flavor

C. pepo var. styriaca: The Styrian oil pumpkin and other thin-hulled or so-called “hull-less” varieties are used for oil production due to the increased yield and reduced need for processing to remove hulls. In these seeds, two layers of the multilayered seed coat are missing and others differentially developed, resulting in a very different appearance:

• Dark green due to thicker chlorenchyma and absence of covering layers
• Outermost layer thin, clear and membranous, sometimes peeling
• Edges narrowed, not covered by a rounded margin; instead, a fine pale ridge may be visible running around edge of seed

Other species of “pumpkin”: The following features may be used to distinguish seeds of C. pepo from seeds of other commonly cultivated edible species:

C. argyrosperma (variable, with some or all of the following features):

• Typically whitish, sometimes with silvery overtones (rarely golden)
• Margin may be ridged or wavy; color gray or light brown, often darker than face of seed
• Thicker than C. pepo, with both faces conspicuously convex and elevated above a narrow margin, often large
• Surface of some varieties may be irregularly cracked, revealing long, narrow epidermal cells like closely packed hairs

C. maxima:

• Usually white, sometimes smooth brown
• Thicker than C. pepo, plump; sometimes over 25 mm long
• Scar at end of neck strongly oblique, often entirely on one side of neck and slanting backwards (not to be confused with an oblique appearance caused mostly by a curve in the neck itself, which is found in all species)

C. moschata:

• Margin brownish, darker than face of seed, which is grayish or tan
• Under magnification, margin usually has irregular surface, appearing wavy, corky or stringy

References:

Bailey LH. The domesticated Cucurbitas—I. Gentes Herbarium (The Kinds of Plants). 1929;2:62–115.

Merrick LC. Systematics and evolution of a domesticated squash, Cucurbita argyrosperma, and its wild and weedy relatives. In: Bates DM, Robinson RW, Jeffrey C, eds. Biology and Utilization of the Cucurbitaceae. Ithaca, NY: Cornell University Press; 1990:77–95.

Merrick LC. Systematics, Evolution, and Ethnobotany of a Domesticated Squash, Cucurbita argyrosperma. Ph.D. Dissertation, Cornell University; 1991.

Russell P. Identification of the commonly cultivated species of Cucurbita by means of seed characters. J Wash Acad Sci. 1924;14:265–269.

Singh D, Dathan ASR. Structure and development of seed coat in Cucurbitaceae. VI. Seeds of Cucurbita. Phytomorphology. 1972 [publ. 1973];22:29–45.

Teppner H. Cucurbita pepo (Cucurbitaceae)—history, seed coat types, thin coated seeds and their genetics. Phyton. 2000;40:1–42.