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American agave, American century plant, centuryplant, maguey americano

Mckelvey's century plant, thorn-crested agave

Habit Plants acaulescent or short-stemmed, commonly suckering, trunks less than 2 m; rosettes not cespitose, 10–20 × 20–37 dm. Plants acaulescent, usually suckering; rosettes densely cespitose, 3–6 × 5–10 dm.
Leaves

erect, spreading to ascending, occasionally reflexed, 80–200 × 15–25 cm;

blade light green to green or glaucous-gray, sometimes variegated or cross-zoned, narrowly to broadly lanceolate, smooth, rigid;

margins nearly straight or undulate to crenate, armed, teeth single, 5–10 mm, 1–4 cm apart;

apical spine dark brown to grayish, conical or subulate, 2–6 cm.

mostly erect, 30–40(–70) × 3–4.5(–5) cm;

blade light green to yellowish green, without bud-prints, linear-lanceolate, stiff, adaxially plane to concave toward apex, abaxially convex toward base;

margins undulate to crenate, nonfiliferous, not easily detached, conspicuously armed, teeth single or occasionally double, 4–6(–8) mm, 1–2 cm apart;

apical spine reddish to grayish, subulate, 1–1.5(–2) cm.

Scape

5–9 m.

3–4.5(–5) m.

Inflorescences

paniculate, not bulbiferous;

bracts persistent, triangular, 5–15 cm;

lateral branches 15–35, horizontal to slightly ascending, comprising distal 1/3–1/2 of inflorescence, longer than 10 cm.

spicate, densely flowered on distal 1/2;

bracts caducous, acicular, 3–5 cm;

peduncle 4 cm or shorter.

Flowers

erect, 7–10.5 cm;

perianth yellow, tube funnelform to cylindric, 8–20 × 12–20 mm, limb lobes erect, subequal, 20–35 mm;

stamens long-exserted;

filaments inserted above mid perianth tube, erect, yellow, 6–9 cm;

anthers yellow, 25–35 mm;

ovary 3–4.5 cm, neck constricted, 3–6(–8) mm.

1 on short pedicel, or 2–7 per cluster, erect, 3.5–4(–4.5) cm;

perianth greenish white to yellowish green, tube campanulate, 2–4 × 8–10 mm, limb lobes erect to slightly spreading, subequal, 14–20 mm;

stamens long-exserted;

filaments inserted on rim of perianth tube, spreading, greenish or lavender, 3–4.5 cm;

anthers pale yellow, 15–20 mm;

ovary 1.8–2.2 cm, neck constricted 5–7 mm.

Capsules

short-pedicellate, oblong, 3.5–8 cm, apex beaked.

sessile or short-pedicellate, oblong and 1.8–2.5 cm or globose and 1.5–2 cm, apex beaked.

Seeds

6–8 mm.

5–6 mm.

2n

= 60.

Agave americana

Agave univittata

Phenology Flowering spring.
Habitat Sandy flats
Elevation 0–100 m (0–300 ft)
Distribution
from USDA
sw United States; Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico
[BONAP county map]
Discussion

Subspecies 2 (2 in the flora).

Various chromosome numbers have been reported for Agave americana under a variety of names, typically without regard to the plant’s origin or its precise taxonomic disposition. Nonetheless, the species is most certainly a polyploid complex based on x = 30, with reports of n = 30 and 2n = 60, 120, and 180 documented by S. D. McKelvey and K. Sax (1933), H. Matsuura and T. Sutô (1935), E. B. Granick (1944), A. K. Sharma and U. C. Bhattacharyya (1962), M. S. Cave (1964), S. Banerjee and A. K. Sharma (1987), Huang S. F. et al. (1989) and B. Vijayavalli and P. M. Mathew (1990). Various dysploids have also been reported (A. F. Dyer et al. 1970; J. L. Strother and G. L. Nesom 1997). See H. S. Gentry (1982) for details.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The name Agave lophantha was mentioned by C. J. W. Schiede (Linnaea 4: 582. 1829) without a description. C. S. Kunth (Enum. Pl. 5: 838. 1850) validated the name, but not before A. univittata was proposed. Neither name is typified nor is any authentic material known. H. S. Gentry (1982) incorrectly retained A. lophantha and it is now widely used. A. J. Breitung (1959) was the first to adopt A. univittata, and that name is taken up here.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Leaves 80–135 cm, 4–6 times longer than wide; capsules 3.5–4 cm.
subsp. protamericana
1. Leaves 100–200 cm, 6–10 times longer than wide; capsules 4–8 cm.
subsp. americana
Source FNA vol. 26, p. 452. FNA vol. 26, p. 449.
Parent taxa Agavaceae > Agave Agavaceae > Agave
Sibling taxa
A. asperrima, A. chrysantha, A. decipiens, A. delamateri, A. deserti, A. desmettiana, A. gracilipes, A. havardiana, A. lechuguilla, A. mckelveyana, A. murpheyi, A. neglecta, A. palmeri, A. parryi, A. parviflora, A. phillipsiana, A. schottii, A. shawii, A. sisalana, A. toumeyana, A. univittata, A. utahensis, A. weberi, A. ×ajoensis, A. ×arizonica, A. ×glomeruliflora
A. americana, A. asperrima, A. chrysantha, A. decipiens, A. delamateri, A. deserti, A. desmettiana, A. gracilipes, A. havardiana, A. lechuguilla, A. mckelveyana, A. murpheyi, A. neglecta, A. palmeri, A. parryi, A. parviflora, A. phillipsiana, A. schottii, A. shawii, A. sisalana, A. toumeyana, A. utahensis, A. weberi, A. ×ajoensis, A. ×arizonica, A. ×glomeruliflora
Subordinate taxa
A. americana subsp. americana, A. americana subsp. protamericana
Synonyms A. heteracantha, A. lophantha
Name authority Linnaeus: Sp. Pl. 1: 323. (1753) Haworth: Philos. Mag. Ann. Chem. 10: 415. (1831)
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