AMORPHOPHALLUS MACRORHIZUS
PROTOLOGUE: Amorphophallus macrorhizus Craib, published in Bull. Misc. Inform. Kew 1912: 419 (1912). The protologue is reproduced below.
SYNONYMS:
HETEROTYPIC SYNONYMS: Amorphophallus longituberosus var. robustus S.Y.Hu in Dansk Bot. Ark. 23(4): 436 (1968) Amorphophallus xiengraiensis Gagnep. in Notul. Syst. (Paris) 9: 123 (1941)
DISTRIBUTION: N. Thailand: Thailand.
DISTRIBUTION NOTE: Northern Thailand — not uncommon in the Doi Suthep-Pui National Park and eastward to Chiang Rai⁴.
SPECIES DESCRIPTION:
Tuber huge, elongate, unbranched or with few branches in lower part, 10-35 cm long, 1.5-6 cm in diam. (top), dirty brown, lacking seasonal offsets. Leaf solitary; petiole 40-110 cm long, 1-2 cm in diam. (base), turgid, densely, velvety hairy; color pattern very variable, from nearly entirely pale green with a few elongate, whitish spots, to reddish brown with many blackish green, large confluent spots, sometimes almost entirely covering the petiole, many intermediate patterns exist often suffused with reddish shades; lamina to 110 cm in diam., leaflets elliptic to obovate, shortly acuminate to apiculate, 10-36 cm long, 5-16 cm in diam., upper side dark, velvety green with a narrow reddish or purplish margin, smooth, lower side greyish green, hairy.⁴
INFLORESCENCE:
Inflorescence solitary, long-peduncled; peduncle like petiole, to 125 cm long; spathe erect, cymbiform, deep, lower part transversely oval, limb triangular, 9-25 cm long, 3-20 cm in diam., base convolute or nearly entirely open, grading into the limb or slightly constricted at the top, lower margins of the limb strongly recurved, outside pale green with some small, darker green spots at the base, the margin suffused with a purplish hue, top dark green, inside pale green with a purplish margin, base green or dirty maroon chequered with pale green or entirely pale maroon, the latter color sometimes extending over nearly the entire spathe, veins at the base impressed, groove-like, in between with very tiny, punctiform warts. Spadix sessile or very shortly stipitate, slightly to distinctly longer than spathe, 11-30 cm long, appendix with or without a few, scattered, blackish, thin hairs.⁴
ECOLOGY:
Found in dry, deciduous dipterocarp-oak forests, on shaley, granitic bedrock in very hard soil, in shaded places; altitude: 300-1500 m⁴
PROPAGATION:
We only attempted rooting this species once in early September and failed to root any cuttings.
ETYMOLOGY:
From Greek makros, “large” or “long,” and rhiza, “root,” literally “large-rooted.” The epithet refers to the species’ exceptionally large, elongate tuber, which may reach approximately 35 cm in length. Although botanically a tuber rather than a true root, historical botanical epithets commonly used rhiza more broadly for conspicuous subterranean structures.
NOTES:
1. Closely related to Amorphophallus cruddasianus (Myanmar) and differing in the possession of the velvety hair-cover on the leaf and the occasional hairs on the appendix, the latter also being much narrower. Amorphophallus macrorhizus is remarkable for the irregular occurrence of hairs on the appendix, a feature unique to the group of species it belongs to.⁴
2. Two names are regarded as synonyms: Amorphophallus xiengraiensis, described by Gagnepain in 1941 from Chiang Rai, and Amorphophallus longituberosus var. robustus.⁴ Craib described the species in 1912 from Kerr's collections at the foot of Doi Suthep near Chiang Mai.²
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus macrorhizus Craib
2. Bull. Misc. Inform. Kew 1912: 419 (1912) — protologue.
3. Alan Galloway — Amorphophallus macrorhizus, alangallowaybotanicals.com.
4. Aroideana 19 (1996):P7 - 131
5. Propagation of Amorphophallus by Leaf Petiole Cuttings — Juniper Level Botanic Garden
6. Amorphophallus xiengraiensis: Notulae Systematicae (Paris) 9: 123(1941)