Boehmeria nivea

Wilmot-Dear, C. M. & Friis, I., 2013, The Old World species of Boehmeria (Urticaceae, tribus Boehmerieae). A taxonomic revision, Blumea 58 (2), pp. 85-216 : 99-102

1. Boehmeria nivea (L.) Gaudich. — Fig. 1 ; Map 2 , 3

Boehmeria nivea (L.) Gaudich.(1830) 499. ― Urtica nivea L. (1753) 985. ― Ramium niveum (L.) Kuntze (1891) 632. ― Type: Unknown collector in Herb. Linn. 1111.19 (lecto LINN, selected by Ghafoor 1977: 18). – See Note 1.

Urtica candicans Burm.f.(1768) 197. ― Boehmeria candicans (Burm.f.) Hassk. (1844) 79. ― Boehmeria nivea (L.) Gaudich. var. candicans (Burm.f.) Wedd. (1869) 207. ― Type: Rumphius, Hortus Amboinensis 5: t. 79 (lectotype, selected here).

Urtica tenacissima Roxb.(1832) 590. ― Boehmeria tenacissima (Roxb.) Blume (1857) 211,f. 56. ― Boehmeria nivea (L.) Gaudich. var. tenacissima (Roxb.) Miq. (1859) 253. ― Type: Roxburgh s.n. (holo BM; iso BR, G), cultivated in Calcutta Botanic Gardens. – See Note 2.

Boehmeria mollicoma Miq. in Zollinger (1854) 100, 104. ― Type: Zollinger 1454 (holo BO, n.v.), Indonesia, Jawa [Java]. – See Note 3.

Boehmeria compacta Blume (1857) 210. ― Type: Unknown collector (possibly Blume) s.n. (holo L), Indonesia, Jawa.

Boehmeria nivea (L.) Gaudich. var. reticulata Blume (1857) 211. ― Syntypes: Blume & Sieber s.n. (L, several collections, presumed syntypes), Japan .

Boehmeria nivea (L.) Gaudich. var. concolor Makino (1909) 251. ― Boehmeria frutescens (Thunb.) Thunb. var. concolor (Makino) Nakai (1927) 515. ― Boehmeria nipononivea Koidz.var. concolor (Makino) Ohwi (1953) 441. ― Boehmeria nivea (L.) Gaudich. forma concolor (Makino) Kitam. in Kitamura & Murata (1962) 208. ― Syntypes: T. Makino s.n. (not traced), Japan,Ryukyu Islands,Yamashiro Island,Takao; K.Ikeda s.n. (not traced), Harima Prov., Mt Masui, 1902.

Boehmeria nivea (L.) Gaudich. var. viridula Yamam. (1932) 50. ― Boehmeria frutescens (Thunb.) Thunb. var. viridula (Yamam.) T. Suzuki (1936) 20. ― Boehmeria nivea (L.) Gaudich. forma viridula (Yamam.) Hatus. (1971) 234. ― Types: Yamamoto 542 (not traced), Taiwan, Kwarenko Pr., Beisan; Suzuki 1168 (not traced), Taiwan, between Doba and Taiheizan, 28 July 1928.

Boehmeria nipononivea Koidz.(1941) 223. ― Boehmeria nivea (L.) Gaudich. subsp. nipononivea (Koidz.) Kitam. in Kitamura & Murata (1962) 208. ― Boehmeria nivea (L.) Gaudich. forma nipononivea (Koidz.) Hatus. (1971) 234. ― Boehmeria nivea (L.) Gaudich. var. nipononivea (Koidz.) W.T. Wang (1981a) 320. ― Type: No material cited or traced.

Boehmeria thailandica Yahara (1981) 4. ― Type: Tagewa et al. 11233 (holo KYO, seen as digital image), Thailand, Phiitsanulok.

Shrub or subshrub, rarely robust herb, 1–4(–7) m tall; ultimate branches robust, 3–4 mm diam, with abundant to dense hairs, these short fine adpressed, or variable (0.1–≥ 0.5 mm long) fine or coarse spreading. Stipules linear-lanceolate, connate in proximal part or free to base, 5–12 by 1–2 mm. Leaves alternate, not or scarcely dimorphic in size, broadly ovate to elliptic (rarely almost orbicular), very variable in size and proportions, 7–20 by 4–18 cm, length (1–)1.52(–3) × width; margin very coarsely dentate, dentate-serrate or crenate, teeth 14–20(–25) either side, these larger on larger leaves (rather than more numerous) and therefore relatively few for size of lamina, ± uniform in size, (2–)3–4 by 4–10 mm, or proximal ones progressively shorter and less distinct; leaf apex usually with abruptly narrowing long acumen (rarely broadly acute); base sometimes cordate, usually truncate or broadly rounded but often abruptly narrowly cuneate at extreme base; basal veins extending into distal half or third of lamina, upper lateral veins (1–)2–3(–4) either side, well-spaced with lowermost arising from proximal quarter or near middle of lamina, inconspicuous on both sides of lamina or finely prominent abaxially; coarser tertiary venation more or less scalariform, most visible abaxially; texture membranous or fairly thin-chartaceous; adaxial surface either glabrous, with sparse coarse cystoliths giving rough feel, or also with sparse hairs, these fine, adpressed, ± 0.4 mm long; abaxial surface with or without shining white tomentum of long tangled hairs varying in density from thick and obscuring coarser reticulation to thinner and patchy with even fine reticulation visible; indumentum on veins and, where tomentum is entirely absent, also on rest of abaxial surface, consisting of sparse to abundant spreading fine hairs of varying lengths, usually longer on main veins, rarely even young leaves soon glabrescent; petiole relatively long, often half of lamina length, (3–) 6–11 cm. Flower­clusters partly axillary but most arranged along specialised and very slender axes 3 –10 cm long, arising as a pair from each axil, mostly much-branched throughout length, often with 2nd–4th-order branching, initial branches often partly dichotomous, successive orders of branching shorter and final branchlets very short <1 cm long; flower-clusters mostly only on one side of axes; bracts minute, broadly triangular, 0.5–1 by 0.3–0.5 mm; plants unisexual or with female inflorescence-bearing axes towards stem apex, male towards base, some axes with both male and female clusters, male towards base; clusters small, 2–4 mm diam, flowers in male clusters recorded as tinged pink, up to 10, in female clusters greenish yellow, 10–30 densely crowded; bracteoles inconspicuous, only up to 0.3 mm long. Male flowers 4-merous, sessile, large, mature buds depressed-globose, 1.5 mm diam, tepals without dorsal appendages, sparsely hairy (hairs spreading). Female flowers narrowly ovoid, 0.5–0.8 by 0.3 mm, with abundant coarse often hooked hairs; stigma often minute, 0.3–1 mm. Fruiting perianth 1–1.5 by c. 0.6 mm, ovoid or ellipsoid without beak, ± flattened, with marginal ridge and often tapering to pedicel region up to 0.3 mm long; surface with conspicuous long spreading hairs.

Distribution ― Presumed native to China, Indochina and Japan, but natural distribution difficult to ascertain. The species has been in cultivation for over 3000 years in China (see Note 7) and is now widely naturalised in the Old World as well as being widely cultivated for fibre.

Habitat & Ecology ― Evergreen forests especially along streams; widely naturalised at forest margins, in ravines and thickets, along roadsides and in other disturbed areas, often on limestone; 70–1700 m altitude.

Conservation status ― Least Concern (LC). It is impossible now to establish the natural distribution of this common, widely cultivated and naturalised species.

Notes ― 1. The authority of B. nivea is normally cited as “(L.) Gaud.” even though Gaudichaud cites Linnaeus’s U. nivea with only a quotation mark. Despite this expression of doubt we have accepted that Gaudichaud in effect made a new combination.

2. The combination B. tenacissima , based on U. tenacissima , was apparently first made by Blume (1857) but he wrongly attributed it to Gaudichaud (1830: 500) where neither the combination nor the epithet appear. Miquel (1859: 243) repeated the error.

3. The name B. mollicoma is tentatively placed in synonymy here since its description conforms to this taxon: “young parts golden-hairy, leaves alternate with long petiole, acuminate, fine-serrate, coriaceous, adult leaves glaucous grey tomentose, rough-hairy adaxially. Female inflorescence-bearing axes axillary dichotomously branched, with interrupted glomerules, fruiting perianth ovoid white-hairy”.

4. “ Boehmeria utilis Blume (1853) 483” – This name is cited by both Blume (1857: 211) and Miquel (1859: 253) in synonymy (under B. tenacissima and B. nivea var. tenacissima , respectively). The reference given is “Indisch Bij. (1853): 483 n. 4”, but we have not been able to trace such a reference, nor have we been able to find the name in any other of Blume’s known works which might have been cited incorrectly.

5. Boehmeria nivea is easily recognisable by its combination of consistently alternate leaves which are often discolorous (indumentum tomentose, with hairs shining, white) and often broader than long and its very slender much-branched peduncles which are usually partly dichotomous, some branches usually with 3rd or 4th-order branching giving a clearly paniculate appearance to the inflorescence architecture. Boehmeria zollingeriana has branched (female) axes and sometimes some leaf-pairs alternate leaves but is so dissimilar in stems glabrescent reddish, leaves with adaxial surface glabrescent, shiny smooth, drying dark brownish black rather than green, abaxial surface with inconspicuous adpressed hairs and male clusters axillary with long-pedicellate flowers, that the two would not be confused.

6. Boehmeria nivea is very variable in density of indumentum on abaxial leaf surface, leaf-size, shape and proportions and in length of marginal teeth although teeth are always relatively few even on large leaves; stigma is very short but variable in length (in Japan and China mostly only 0.3–0.5 mm long; in Indochina, Thailand, Indonesia usually 0.5–1 mm long). Variants have often been recognised formally at the level of species, variety or form, distinguished on characters such as size of leaves, shape of leaf base, length of acuminate apex, density or presence or absence of white tomentum on abaxial leaf surface and stipules connate or free, but a range of intergrading forms exists with all characters varying independently such that formal distinction is artificial.

Walker (1976: 413) stated that it was not possible to define limits between the varieties which had been formally described as present on Ryukyu Islands and Weddell (1856: 391), in discussing the variation, had earlier come to a similar conclusion. However, Yahara (1981: 4), while noting the widely varying density of indumentum, formally distinguished those forms which entirely lack white tomentum as B. thailandica . He stated that they are distinctive also in unbranched habit, very thin-textured leaves and more extensively branched inflorescence-bearing axes often longer (rather than shorter) than petiole of subtending leaf, and restricted to tropical dry evergreen forest, whereas discolorous forms occur in disturbed vegetation and dry soil. We have seen similar thin-leaved concolorous material in China , Vietnam and Japan (Ryukyu Islands), often with particularly narrow leaves (length up to 3 × width), much narrower than any seen in the white form, but the distinctions mentioned by Yahara do no hold up because we have observed sparsely white-tomentose forms also having thin-textured leaves and extensively branched inflorescence-bearing axes and occurring in undisturbed habitat, and similar concolorous material sometimes occurring in disturbed or degraded forest. Therefore a formal distinction between strictly concolorous and sparsely discolorous forms cannot be maintained on grounds of either habitat or morphology.

7. Chen et al. (2003: 167) states that it is now widely cultivated in eastern Asia, especially China, where the history of cultivation can be traced back at least 3000 years. The species was introduced to Europe and the Americas in the 18th century. They suggest that B. nivea originated in eastern Asia and that forms with white tomentum absent or very sparse may be the original wild form. Our observation that entirely concolorous forms seem to be restricted to eastern Asia and are mostly found in relatively undisturbed vegetation together with forms with erratic patches of thin sparse tomentum, whereas forms with dense white or grey tomentum are mostly found in disturbed areas, supports this suggestion. However, since these sparsely tomentose forms have a wider distribution and wider habitat-range and also grade into the clearly discolorous entity via a continuous series of intermediate forms, it is not possible to define and recognise formally this supposed naturally-occurring variety. As discussed above, separation of merely those forms with leaves entirely lacking white tomentum from similar and apparently also naturally-occurring but sparsely tomentose forms would be artificial and misleading. We therefore here treat the variation as one polymorphic taxon at the rank of species. Nevertheless, a separate map of the completely concolorous variants has been provided ( Map 3 ), since, even without being able to include the full range of the putative original wild form, it shows clearly the restriction of these variants to eastern Asia.

8. Concolorous forms are sometimes mistaken for two consistently opposite-leaved taxa. Boehmeria polystachya (Himalayas, China) is distinguished by tertiary leaf-veins more robust, inflorescence-axis with only 2nd-order branching and a winged fruiting perianth. When inflorescence-bearing axes are only small and little-branched, concolorous forms can be confused with the widespread B. virgata subsp. macrophylla var. macrostachya which differs in inflorescence-axis only branched near base and with only 1st-order branching.

9. Discolorous forms would not be mistaken for other species of Boehmeria , but, when sterile, are frequently confused with discolorous-leaved species in other genera of the tribe, especially Oreocnide frutescens (eastern and south-eastern Asia), Debregeasia australis ( Australia) and various species within Leucosyke once separated as Maoutia (Asia and the Pacific). Fertile material is easy to distinguish since all three genera have a capitate stigma and inflorescence-bearing axes strictly dichotomously branched, with all clusters at the apex of branches rather than mostly laterally branched with clusters lateral as well as terminal on branches.Additionally, Oreocnide also has a conspicuous fleshy receptacle surrounding each fruiting perianth, and the leaves of O. frutescens are always relatively narrow, sometimes obovate. Debregeasia australis has much more conspicuous leaf venation than B. nivea because the white tomentum is almost absent from veins, and the apex of its fruiting perianth opens with a ‘mouth-like’ slit rather than being tightly constricted as normally seen in Boehmeria . Leucosyke has a very short perianth not reaching the base of the stigma, often also thick-textured bullate leaves. However, sterile material of L. puya and related Pacific taxa can be impossible to distinguish with certainty, although their leaves have less clearly scalariform tertiary venation than B. nivea . Pipturus argenteus , also discolorous-leaved, is distinguished by stigmas long, straight and caducous, inflorescence-bearing axes solitary in axil and tomentum less bright white, consisting of extremely short hairs, this tomentum also present on male and female flowers.

Figures

Map 2 Distribution of Boehmeria nivea (L.) Gaudich. (discolorous).

Map 3 Distribution of Boehmeria nivea (L.) Gaudich. (concolorous).

Fig. 1 Boehmeria nivea (L.) Gaudich. a. Female branch;b. male branch;c, d. leaves of varying form;e. discolorous leaf, detail of abaxial surface; f. concolorous leaf, detail of abaxial surface; g. stipule; h. detail of male inflorescence-bearing axis with two flower-clusters; i. male bud; j, k. details of female inflorescencebearing axes with (j) congested and (k) loosely arranged flower-clusters;l-n. fruiting perianths of different form (l and m from same plant) (a, f, k: Henry 12542, K; b, g-i: Suddee 968, K; c, e, j, n: Balansa 2508, K; d: Teijsmann s.n., L; l, m: Hansen 12748, K). — Scale bars: a-d = 2 cm; e-h, j, k = 2 mm; i, l–n = 1 mm.