Hylocereus undatus
Cactaceae subfam. cactoideae
night-blooming cere us, nightblooming cactus
diffuse, taproots, or tuberlike, sometimes adventitous.
usually sharply 3-angled, to 500+ × 4–7.5 cm;
ribs with undulate margins and gray, hornlike bark;
areoles 2 mm diam.
segmented or unsegmented, usually conspicuously succulent with thick cortex and pith, surface usually ribbed or tuberculate, usually somewhat woody with wood confined to internal ring, bark sometimes becoming proximally hardened and woodlike;
areoles circular to linear [protracted into finger-shaped shoots in Neoraimondia of South America], hourglass-shaped in some genera, with spiny portion separated from flowering portion by a groove in the stem surface, spiny areoles completely separate from flowering areoles in some genera, bearing 0–90 spines, glochids absent.
absent or rudimentary and microscopic or nearly so, less than 1 mm.
1–4 per areole, brownish gray, inconspicuous.
acicular, subulate, daggerlike, ribbonlike, hairlike, or bristlelike, smooth, rough, striate, or annulate-ridged, glabrous (rarely pubescent), epidermis intact, not separating as sheath.
fragrant;
outer tepals white, outermost strongly reflexed, midstripes yellowish green;
inner tepals white, broad, oblanceolate;
filaments 50–75 mm;
style cream, 175–200 mm.
diurnal to nocturnal, bisexual (rarely unisexual or functionally so), solitary in areoles (rarely several), radially symmetric (rarely bilateral), sessile, broadly salverform, urceolate, funnelform, or long tubular;
flower tube epigynous, usually conspicuous, adnate to upward extension of stem surrounding ovary, 0.2–15[–30] cm;
triangular leaflike bracts or small scales sometimes present on ovary and flower tube;
nectary often apparent, forming open chamber surrounding base of style.
spheric to oblong.
dehiscent or indehiscent, depressed-spheric or spheric to long clavate, juicy, fleshy, or dry;
perianth persistent or deciduous.
2 × 1 mm.
1–3000+, yellowish, reddish, brown, or black, spheric, comma-shaped, lenticular-reniform, pyriform, or obovoid, 0.4–5 mm, rarely strophiolate, never arillate.
= 22.
Hylocereus undatus
Cactaceae subfam. cactoideae
Hylocereus undatus is sporadically naturalized in tropical and subtropical regions worldwide where it is cultivated for its large, edible fruits and beautiful flowers, which are among the largest in the cactus family. In Florida, H. undatus has escaped from cultivation in nine counties, forming large colonies in some areas. Individuals of this species grow prolifically and may soon overrun their substrate. Whether populations of H. undatus in the United States are merely persisting or are also reproducing sexually remains unclear.
The vernacular name night-blooming cereus has been applied to several genera of cacti with large, nocturnal flowers.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera ca. 111, species ca. 1500 (28 genera, 121 species in the flora).
Subfamily Cactoideae is the most diverse group of the Cactaceae, in terms of size, architecture, habitat, and habit. The vast majority of North American species are xerophytic, with columnar to spheric or barrel-shaped stems. A few are geophytic, that is, stems are mostly deep-seated in the soil substrate, often with the plant consisting mostly of an enlarged taproot and the visible parts of the stems appearing nearly flush with the soil surface or nearly buried during drought, becoming taller and slightly more conspicuous only during the growing season. Fewer species still, are epiphytic, and those only in the tropical and subtropical regions of North America and South America.
In the following treatments, most authors have attempted to recognize varieties wherever current evidence is compelling. Where evidence is equivocal, our tendency has been to include greater variability within varieties and, hence, fewer formal trinomials. Unfortunately, in the absence of strong supporting evidence, herbarium specimens of cacti are usually inadequate for the purpose of making taxonomic decisions. As a consequence, some populations of conservation interest here have been placed into synonmy before critical studies have been conducted to determine quantitatively and objectively how distinct each population is, or which deserve varietal status. Authors do not intend to imply that other varieties should not eventually be recognized. More systematic work, including DNA research and field research of all variants, is needed as a prelude to reassessing the status of currently listed and proposed populations. Such populations need to be protected during the entire phase of analysis and reassessment.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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