Cucurbita

Plants sometimes shrublike in cultivated forms of C. melopepo, annual or perennial, monoecious, procumbent and trailing or climbing; stems (annual, often sulcate or angled), hairy; roots tuberous or fibrous or a taproot; tendrils 2–7-branched or absent. Leaves: blade suborbiculate to broadly ovate, ovate-lanceolate, reniform, or triangular, usually deeply to shallowly palmately (3–)5(–7)-lobed, sometimes unlobed or 2-lobed, lobes depressed-ovate, ovate, broadly or narrowly triangular, or obovate to lanceolate, oblanceolate, oblong-lanceolate, or subrhombic, (base truncate to cordate), margins serrate to denticulate or mucronulate, surfaces eglandular or glandular, glands scattered, sessile or stipitate to peltate. Inflorescences: staminate flowers solitary [in axillary fascicles]; pistillate flowers solitary, from different axils than staminate; floral bracts absent. Flowers: hypanthium campanulate, cylindric, or cupulate; sepals 5, (straight, erect), subulate-linear to lanceolate [spatulate]; petals 5, (often recurving), connate 1/2 length, cream or yellow to orange, broadly ovate to oblong-ovate, oblong-elliptic, triangular, triangular-ovate, or lanceolate-ovate, 25–90[–120] mm, pubescent to puberulent, corolla campanulate. Staminate flowers: stamens 3; filaments inserted at hypanthium base, distinct or slightly connate; thecae connate, forming central oblong body, sigmoid-flexuous, connective narrow; margins differentiated or not in thickness, texture, and color, surface smooth or slightly rough to punctate-sculptured. x = 20.

Distribution

North America, Mexico, West Indies, Central America, South America, introduced nearly worldwide.

Discussion

Species of Cucurbita have long provided fruits that are staples of the world’s diet. Radiocarbon dates for C. pepo from Guilá Naquitz Cave in subtropical central Oaxaca, Mexico, document the earliest known cultivation of a squash––between 10,000 to 8000 calendar years ago (B. D. Smith 1997)––predating the appearance of maize, beans, and other directly dated domesticates in the Americas by about 4000 years. The oldest known cultivated maize cobs also have come from Guilá Naquitz Cave, dated about 6250 calendar years ago. Cultivated cucurbits were introduced into the Old World quickly after the discovery of the New World (H. S. Paris et al. 2006), and since the 17th century they have spread over the tropics and subtropics and temperate regions. After its introduction to the Old World, C. pepo apparently underwent secondary diversification in Europe and/or Asia Minor (J. R. Harlan 1951).

Cucurbita has been divided into two groups (T. W. Whitaker and W. P. Bemis 1975): the arid-zone perennials with tuberous storage roots, and the more mesophytic annuals or short-lived perennials without storage roots. Four of the domesticated species (C. argyrosperma K. Koch, C. maxima, C. moschata, and C. pepo) plus one wild species (C. ecuadoriensis Cutler & Whitaker) comprise the mesophytic lineage (O. I. Sanjur et al. 2002). One other among the mesophytic domesticated species, C. ficifolia, is outside the mesophytic clade and basal to it.

Uncertainty about the number of species in the genus reflects two areas of subjectivity: some domesticated species are commonly treated as conspecific with a wild species when a derivative-progenitor relationship is indicated––the domesticated Cucurbita maxima arose from the wild C. andreana Naudin of South America; and, the taxonomic status of some entities is not unambiguously resolved––C. digitata was treated by M. Nee (1990) to include four taxa, three of which are sometimes treated as distinct species. In any case, the geography and morphology of all the entities potentially treated at specific rank is fairly well understood. Additionally, Nee has noted that a wild ancestor of C. moschata, from reports from Colombia, may remain to be discovered and described; similarly, he has predicted that the wild ancestor of C. ficifolia exists somewhere in the Andes.

Four of the domesticated species are treated here because they sometimes are encountered in the flora area outside of cultivation; in most cases, these plants can be characterized as waifs, as they apparently do not maintain themselves in persistent populations for more than one or a few years.

Cucurbita argyrosperma K. Koch (Japanese pie pumpkin, white cushaw) is currently grown in the United States and known to have been in cultivation in eastern North America since pre-Columbian times (G. J. Fritz 1994); it has not been reported to grow outside of cultivation in the flora area.

Identification of species among plants of domesticated Cucurbita often is difficult (especially among C. maxima, C. melopepo, C. moschata, and C. pepo) because habit, vestiture, leaf shape, and floral characters commonly show parallel variation, and fruit shape and size are highly variable.

Species 14–22 (9 in the flora).

Selected References

Bailey, L. H. 1943. Species of Cucurbita. Gentes Herb. 6: 266–322.

Bemis, W. P. and T. W. Whitaker. 1969. The xerophytic Cucurbita of northwestern Mexico and southwestern United States. Madroño 20: 33–41.

Decker, D. S., T. W. Walters, and U. Posluszny. 1990. Genealogy and gene flow among annual domesticated species of Cucurbita. Canad. J. Bot. 68: 782–789.

Nee, M. 1990. The domestication of Cucurbita (Cucurbitaceae). Econ. Bot. 44(3,suppl.): 56–68.

Rhodes, A. M. et al. 1968. Numerical taxonomic study of Cucurbita. Brittonia 20: 251–266.

Sanjur, O. I. et al. 2002. Phylogenetic relationships among domesticated and wild species of Cucurbita (Cucurbitaceae) inferred from a mitochondrial gene: Implications for crop plant evolution and areas of origin. Proc. Natl. Acad. Sci. U.S.A. 99: 535–540.

Whitaker, T. W. and W. P. Bemis. 1975. Origin and evolution of the cultivated Cucurbita. Bull. Torrey Bot. Club 102: 362–368.

Wilson, H. D. 1990. Gene flow in squash species. BioScience 40: 449–455.

Wilson, H. D., J. Doebley, and M. Duvall. 1992. Chloroplast DNA diversity among wild and cultivated members of Cucurbita (Cucurbitaceae). Theor. Appl. Genet. 84: 859–865.

Lower Taxa

Cucurbita digitata, Cucurbita ficifolia, Cucurbita foetidissima, Cucurbita maxima, Cucurbita melopepo, Cucurbita moschata, Cucurbita okeechobeensis, Cucurbita palmata, Cucurbita pepo

Key

1	Leaf blades unlobed or shallowly 2-lobed, longer than broad.	Cucurbita foetidissima
2	Midveins of leaf lobes not adaxially densely hispidulous-strigillose with white hairs; tendrils eglandular; plants usually annual, rarely short-lived perennial; roots taproots or fibrous	> 4
3	Leaf blade sinuses nearly or completely to petiole, lobes narrowly lanceolate to narrowly oblanceolate or oblong-lanceolate.	Cucurbita digitata
3	Leaf blade sinuses 1/2–2/3 to petiole, lobes lanceolate-acuminate to triangular or triangular-lanceolate.	Cucurbita palmata
4	Corollas cream to pale creamy yellow; stems glabrous or glabrate to coarsely hirsute or villous with flattened, vitreous hairs, rarely sparsely short-hispid, without pustulate-based hairs; fruit flesh intensely bitter.	Cucurbita okeechobeensis
5	Stems villous to hirsute or puberulent to pubescent, or combination, usually without pustulate-based hairs	> 7
6	Stems hispid with persistent, strongly pustulate-based hairs and hispidulous-hirsutulous understory.	Cucurbita pepo
6	Stems densely puberulent to hirsutulous, scattered longer hairs with strongly to weakly pustulate bases absent or present.	Cucurbita melopepo
7	Peduncles in fruit relatively soft, corky-thickened, terete, not prominently ribbed, not abruptly expanded at point of fruit attachment.	Cucurbita maxima
7	Peduncles in fruit hardened, woody, 5-ribbed, abruptly expanded or not at point of fruit attachment	> 8
8	Peduncles in fruit abruptly expanded at point of fruit attachment; sepals narrowly lanceolate; fruit flesh usually yellow to orange to greenish; seeds whitish to cream or light brown, surface ± punctate-sculptured, margins raised-thickened and ± undulate, golden yellow to silvery.	Cucurbita moschata
8	Peduncles in fruit slightly expanded or not at point of fruit attachment; sepals linear to linear-lanceolate or subulate-linear; fruit flesh white to whitish or yellow to light orange or greenish; seeds dark brown to black or whitish to cream or tawny, surface ± smooth, margins raised-thickened and smooth, colored as seed surface	> 9
9	Anther filaments glabrous; fruit flesh usually yellow to light orange to greenish or whitish, bitter or not; seeds whitish to cream or tawny.	Cucurbita melopepo
9	Anther filaments short-villous; fruit flesh usually white, sweet; seeds usually dark brown to black, sometimes whitish.	Cucurbita ficifolia