Boehmeria ourantha Miq.

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 : 178-181

25. Boehmeria ourantha Miq. – Fig. 31; Map 32

Boehmeria ourantha Miq.(1851) 33. ― Boehmeria caudata (Burm.f.) J.J.Sm. var. ourantha (Miq.) J.J.Sm. (1910) 714. ― Boehmeria platyphylla D.Don var. ourantha (Miq.) Hochr. (1925) 344. ― Type: Junghuhn s.n. (holo U), Indonesia, Jawa [Java], Bantam Dist. – See Note 1.

Boehmeria pseudotomentosa Yahara (1981) 16, syn. nov. ― Type: Shimizu et al. 22457 (holo KYO, n.v.), north-eastern Thailand, Phu Kradung. – See Note 2.

Boehmeria tomentosa sensu auct.,incl.Wedd.(p.p.), non B.tomentosa Wedd. s.str.; B. macrophylla Hornem. var. tomentosa (Wedd.) D.G.Long , sensu D.G.Long,non var. tomentosa (Wedd.) D.G.Long , s.str. – See Note 3 and 5.

Robust erect subshrub or shrub, 0.1–2(–4) m tall; ultimate stems robust, 2 –3 mm diam, hairs dense, spreading, soft golden-brown, (0.5–) 1–2 mm long; eventually glabrescent. Stipules conspicuous, narrowly triangular, tapering to apex, (5–)6–11 by 2– 3 mm, length 3 × width, thin(–thick)-textured, densely hairy outside on midrib. Leaves opposite, not or moderately dimorphic in size only, ‘larger’ leaf with length of lamina 1–1.5 ×, but petiole 1–2(–2.5) ×, length of ‘smaller’ ones; broadly ovate or deltate, at least some usually medium or large, (7–)10–20 by (5.5–) 7–15 cm, length (0.8–)1.3–1.5(–1.8) × width; margin dentate, most or all leaves with (20–)25–30(–33) medium-sized teeth either side, teeth 2–3 by 4–6.5(–8) mm (wider rather than more numerous on largest leaves but some of the smallest leaves with only c. 17 teeth, these 1.5 by 3 mm), their width 2–3 × length, acute or obtuse but mucronate, slightly up-curved (their upper margin convex or ‘S’-shaped), ± uniform size but leaf margin entire near base; leaf apex acute, short-attenuate or indistinctly acuminate, acumen consisting mainly of one short broad apical tooth only 1.5–3 × length of marginal teeth and length often only 2 × width, usually rounded at tip; base symmetrical or almost so, ± truncate or broadly shallowly cordate (rarely broad-cuneate or broadly rounded); basal veins extending into distal half of lamina, upper lateral veins 1–2 either side, similarly arranged in both sides or sometimes 3 veins on one side, lowermost arising near middle of lamina or all arising in distal half, basal veins thinly prominent abaxially, upper veins and reticulation rather indistinct; texture thin- or thick-chartaceous; both surfaces velvety with spreading hairs like stem, so dense as to give golden sheen to leaf, or sometimes shorter and sparser adaxially (rarely both sides); petiole quite variable relative to lamina, 0.15–0.25(–0.3) × lamina length. Flower­clusters borne on leafless inflorescence-bearing axes, these ± erect, unbranched, 1 per axil, (4–)6–10(–15) cm long; entirely male axes sometimes present in lower part of plant, upper axes either entirely female or bisexual with mainly female flowers, male flowers being either restricted to a few male clusters at extreme apex or as scattered flowers in mainly female clusters, more numerous towards axis apex and with uppermost clusters sometimes entirely male; flower-clusters ± contiguous or male ones often (female rarely) spaced up to 2 mm apart, entirely male clusters only 2–3 mm diam, with few–15 flowers; entirely female clusters (2–)5–6(–8) mm diam, with c. 40–more than 100 flowers; bracts 2–3 by 1–1.5 mm, narrowly or broadly triangular with narrowly acute tip, sometimes conspicuous in male clusters; bracteoles variable in shape and size, obovate or spathulatelanceolate, 0.5(–1) mm long but inconspicuous in the densely congested clusters. Male flowers 4-merous, subsessile or on pedicels up to 1 mm, mature buds globose, c. 1.5 mm diam, tepals with prominent dorsal appendage; hairs dense, short, spreading. Female flowers flattened-ovoid, c. 1 by 0.3–0.5 mm, tapering to apex, densely hairy; stigma 1–1.5(–2) mm. Fruiting perianth quite variable in shape and proportions, ovoid to ellipsoid or obovoid and often 3-angled, 1.5–2 by (0.5–) 1–1.5 mm with apex acute, rounded or truncate, rarely with indistinct beak, moderately laterally flattened, sometimes more flattened around the achene forming a ± distinct rim or narrow indistinct wing, with dense spreading hairs in distal half. Achene occupying most of fruiting perianth, ovoid.

Distribution ― North-eastern India, Burma, Thailand, south-western China, Indonesia (Jawa).

Habitat & Ecology ― Dense evergreen forest, open scrub, grassland, disturbed land (old cultivations), roadside banks (under Cinchona ); 1000–2300 m altitude.

Conservation status ― Near Threatened (NT). The species is known from c. 50 collections, some of which are recent. The EOO of 3 372 270 km 2 is misleading due to the distance between Jawa and its known localities in Indochina, but its AOO of less than 500 km 2 suggests that it is at risk. It occurs in 15 rather scattered locations, and in fairly restricted forest habitat. Although the habitats in many of its localities are not currently threatened by serious degradation, and it therefore does not meet the criteria for a formal status of Vulnerable (VU), it may become so in the future with increasing agriculture in these regions.

Notes ― 1. Blume (1857: 221) cites the name of this species as “ B. urantha ” but refers it to Miquel, so it is considered an orthographic error, not a new name.

2. The holotype of B. pseudotomentosa has not been seen but most other collections cited in the original description have been studied. Yahara (1981) in describing B. pseudotomentosa noted its general resemblance to B. ternifolia (see Note 7) and the similar inflorescence architecture to that of B. yaeyamensis (see Note 4); he also noted the earlier misapplication of the epithet tomentosa (see Note 3) to his ‘new’ species but was apparently unaware that the earlier name B. ourantha applied to this entity.

3. See under B. virgata subsp. macrophylla var. tomentosa for discussion of this confusing situation of valid publication of a new combination based on application of epithet to a different taxon.

4. Boehmeria ourantha is distinctive in its male flowers arranged at the apex rather than base of mainly female inflorescence-bearing axes, its long spreading golden indumentum (often at least 2 × the length of hairs seen in most other taxa) which is often so dense on most parts as to give a distinctive golden sheen to the plant and its broad truncate to cordate velvety leaves. It was reduced to a variety of the very variable entity B. virgata subsp. macrophylla (as B. caudata (Burm.f.) J.J.Sm. var. ourantha ) by Smith (1910) who is stated by Hochreutiner (1925) to have seen collections originally identified by Miquel, but it is here considered worthy of recognition as a species because of this unusual arrangement of male flowers. In most species of Boehmeria including B. virgata , male flowers, if found on a mainly female axis, are located in the basal part, often on short entirely male branches; in B. virgata male flowers also differ in being subsessile rather than pedicellate. Only B. pilosiuscula (sympatric) and B. yaeyamensis (allopatric, Ryukyu Islands) have the same unusual arrangement of male flowers; these two taxa also resemble it in their densely congested female clusters giving a distinctively cylindrical appearance to the fruiting axis but differ in their stem indumentum of mixed minute and long hairs not giving a golden sheen. Boehmeria pilosiuscula also differs in smaller leaves with a distinctly oblique base and B. yaeyamensis in broadly crenate leaves.

5. Hochreutiner (1925), in making the new combination B. platyphylla var. ourantha , noted the apical male clusters on unbranched bisexual axes and the long indumentum as distinctive, suggesting that var. ourantha might be worthy of recognition as a species but not wishing to over-ride existing taxonomy. He also noted it as distinct from the Malagasy entity bearing the epithet “ tomentosa ” (here placed as B. virgata subsp. macrophylla var. tomentosa (Wedd.) Friis & Wilmot-Dear ).

Nevertheless, the misapplication of the epithet “ tomentosa ” to material of B. ourantha has continued in much subsequent literature (e.g., Chen et al. 2003: 170). Most confusingly, the combination B. macrophylla Hornem. var. tomentosa (Wedd.) Long , based on the Afro-Malagasy B. tomentosa Wedd. , was misapplied for Asian material in the Flora of Bhutan ( Grierson & Long 1983: 126). Boehmeria virgata subsp. macrophylla var. tomentosa (Wedd.) Friis & Wilmot-Dear is an Afro-Malagasy taxon and in addition to the different arrangement of male flowers is also rather dissimilar in its overall appearance with velvety but whitish indumentum giving a grey rather than golden cast to the plant, leaves narrower and not truncate with teeth smaller, more numerous (35–40) and inflorescence-bearing axes long, slender with well-spaced clusters.

6. Hochreutiner (1925) also remarked that B. ourantha somewhat resembled B. rotundifolia (= the Himalayan B. virgata subsp. macrophylla var. rotundifolia ); the partly sympatric subsp. macrophylla vars. macrostachya and scabrella are also sometimes similar to B. ourantha in general appearance; the first two varieties are easily distinguished by hairs on the stem and adaxial (often also abaxial) leaf surface inconspicuous adpressed, var. scabrella by its short usually adpressed stem indumentum, leaves often smaller with teeth smaller relatively narrower and hairs stiffer giving a rough texture to the surface; both var. rotundifolia and var. scabrella are also distinguished by the entirely male inflorescence-bearing axes being branched, and var. rotundifolia by its leaf apex abruptly narrowly long-acuminate.

7. Forms of the sympatric but less widespread B. ternifolia var. ternifolia with densely-pubescent stems and leaves are very easily confused with B. ourantha but differ in the leaf apex abruptly acuminate consisting of an apical tooth which is usually long and tail-like and/or constricted at its base; inflorescence-bearing axes are also usually less congested, never bisexual and the male ones are often branched; the indumentum is also usually shorter (≤ 0.3 mm) and sparser and thus does not give a distinctive golden sheen to the plant; the leaf margin usually bears less than 25 teeth either side and the distal teeth are often progressively markedly wider than the lower ones.

8. The more densely hairy forms of B. holosericea ( Japan, South Korea), allopatric but rather similar in its leaf shape and its erect often thick female inflorescence-bearing axes with large crowded clusters, are distinguished by male flowers (sessile) on separate pendulous axes, minute stem hairs, rounded and outward-pointing marginal teeth of their often thinner-textured leaves.

Figures

Map 32 Distribution of Boehmeria ourantha Miq.