Boehmeria sieboldiana Blume

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 : 183-185

27. Boehmeria sieboldiana Blume — Fig. 33 ; Map 34

Boehmeria sieboldiana Blume (1857) 220. ― Boehmeria platyphylla D.Don var. sieboldiana (Blume) Wedd. (1869) 213. ― Syntypes: Herb Siebold s.n. [L 908.185-1370] (L), Japan; Siebold s.n. [L 908.185-1446] (L), Japan; Burger s.n. [L 908.185-1420] (L; isosyn P), Japan.

Perennial herb, up to 1.3 m, often robust and thick-stemmed (up to 8 mm diam), ultimate stems (1–) 1.5–2 mm diam; hairs very sparse to abundant, fine, adpressed. Stipules long and narrow, 4–9 by 1–1.5 mm, with long-acuminate apex. Leaves opposite, not or slightly dimorphic, with length of ‘larger’ leaves up to 1.4 × ‘smaller’ ones and relatively narrower, and narrowly ovate or ovate-attenuate to rhombic-ovate, rarely very narrowly elliptic-ovate, most leaves medium or large, (8–)10–20 by 3.5–10 cm, length 2–3(–4.5) × width (leaves near base of stem often longer and relatively broader, up to 24 by 15 cm, length only 1.5 × width); marginal teeth (13–)15–30(–40) either side, large, acute, often relatively narrow, mostly outward-pointing (upper margin straight or slightly convex), usually fairly uniform in size (0.5–)2–5(–10) by (3–)5–9(–15) mm (rarely distal ones larger, up to 1.5 × broader but not markedly longer than proximal ones and with their upper margin slightly concave); leaf apex attenuate-acuminate with a single fairly long tooth up to 0.2(–0.25) × total lamina length; base broadly rounded or slightly cordate or rounded with abruptly short-cuneate extreme base; basal veins reaching distal third of leaf, upper lateral veins 3 –5 either side but scarcely distinguishable from coarser tertiary venation, lowermost arising near middle of lamina, these and the somewhat scalariform coarser tertiary venation visible but not prominent abaxially; texture membranous or thin-chartaceous, rarely thicker and leaves slightly bullate (but see Note 3); surface glabrous or sometimes (especially very young leaves) with hairs both sides, these very sparse, long; abundant minute cystoliths visible adaxially in dry state; petiole 0.25–0.5 × lamina length. Flower­clusters borne on leafless inflorescence-bearing axes, these unbranched, ± erect, 8 –more than 20 cm long, uni- or bisexual with female clusters in upper part; clusters usually fairly well spaced 1–4 mm apart giving slender appearance, rarely almost contiguous; male clusters small, 1–2 mm diam, with few–10 flowers, female clusters 1.5–3 mm diam (up to 4(–5) mm in fruit), with 10–50 loosely arranged flowers; bracteoles obovate, inconspicuous, c. 0.3 mm long. Male flowers 4-merous, sessile, lobes divided more or less to base, mature buds depressed-globose, c. 1.5 mm diam, tepals without dorsal appendages, hairs sparse, adpressed. Female flowers broad-ovoid, often relatively flattened, c. 0.7 by 0.3 mm; stigma of varying length, 0.3–2 mm long. Fruiting perianth either broadly ovoid to obovoid sometimes tapering to indistinct pedicel, only moderately laterally flattened but with distinct marginal rim or ± winged, or rhombic to subglobose with broadly rounded base, not or scarcely laterally flattened and without marginal rim; 1–2.5 by 0.7–1.5 mm, length usually less than 1.5 × width; glabrous or very sparsely adpressed-hairy.

Distribution ― South Korea (Jeju ‘Quelpart’ Island), Japan (Honshu,Shikoku,Kyushu, Ryukyu Islands),southern and south-eastern China.

Habitat & Ecology ― Dense forest on Eocene limestone, littoral forest, secondary forest, thickets, margins of cultivation, often in partial sun in moist soil by streams or on coral; 10– 1400 m altitude.

Conservation status ― Least Concern (LC). It is known from more than 200 collections from many locations in a wide range of habitats, and some of these collections are recent. Separate formal assessments are not given for the two, intergrading, varieties.

Notes ― 1. This species is distinctive in its leaves rhombic or rhombic-ovate, fairly narrow (‘nettle-like’) ± glabrous and usually thin-textured, marginal teeth fairly uniform, large but relatively narrow, flower-clusters relatively small and well-spaced.

2. Two varieties of B. sieboldiana are recognised. Var. fuzhouensis is considered worthy of recognition in its possession of several correlated characters and its apparent restriction to part of the species range, but recognised only at varietal level due to the existence of several intermediate collections from part of the same region (Zhejiang).

3. Forms of B. sieboldiana var. sieboldiana with marginal teeth slightly larger towards the leaf apex are difficult to distinguish from some forms of B. japonica , which is partly sympatric with B. sieboldiana , extending to Northern China and Northern Japan (Hokkaido) but absent from Ryukyu Islands. Boehmeria japonica differs from B. sieboldiana mainly in its leaves ovate (rather than mostly rhombic-ovate) with cuneate to truncate base, also mostly relatively broader (length rarely up to 2 × width); leaves differ in one or usually two of the following characters of the marginal teeth: distal ones progressively markedly larger than proximal; or all teeth markedly up-curved; or teeth very few (only up to 12 either side) and very long such that leaf appears laciniate, leaves then also often being smaller than in B. sieboldiana with their terminal tooth often comprising up to half of lamina length. Some forms of B. japonica have spreading hairs, the inflorescence-bearing axes are sometimes branched, and its fruiting perianth is often broadly-winged. Differences are discussed in detail under B. japonica (see Note 12). Material somewhat intermediate (possibly hybrid) between the two species includes the type collections of B. kiusiana and B. sieboldiana var. ovata , which are cited under B. japonica var. japonica (see Note 7).

4. Material intermediate in appearance with B. holosericea (sympatric but less widespread: Japan, South Korea) occurs in Japan. Boehmeria holosericea differs from B. sieboldiana in leaves thicker, broader, sometimes somewhat bullate with short distinct acumen, fewer veins, female axes with large contiguous clusters and most parts of plant usually with spreading indumentum. In the intermediate material leaves are relatively broader and mostly more thick-textured than in B. sieboldiana , female axes have flower-clusters large and contiguous and fruiting perianth sometimes broader-winged and tapering. This entity, described as B. egregia Satake , was considered by Kitamura & Murata (1961) as intermediate, possibly a hybrid with B. splitgerbera, Ohba (2006: 108) similarly suggested it to be a hybrid between B. sieboldiana and B. splitgerbera , but Yahara (1983a) thought hybridisation unlikely because it lacks any of the distinctive characters of B. splitgerbera (two kinds of hairs, bilobed leaves, bifurcated main veins). He suggested the possibility of parallel evolution, but it could equally be considered, and is here considered, as intermediate (possibly a hybrid) with B. holosericea . This intermediate material includes the type of B. egregia , which is therefore cited below.

5. Walker (1976: 413) noted similarly thicker- and broader-leaved variants (also with longer stigma and fruiting perianth) in Ryukyu Islands (which he referred to as B. sieboldiana , referring to the thin-leaved ones as B. formosana even though the types of both names have thin narrow leaves), but suggested that the two entities were probably variants of a single species.

The following type and the name based on it represents material intermediate with B. holosericea :

Boehmeria egregia Satake (1936) 487. — Type: Satake 3522

(holo TI; iso TI), Japan, Honsyu, Izu Province, Izu Osima

ls., 9 Sept. 1935.

Key to varieties

1. Leaves narrowly ovate or rhombic-ovate, length 2–3 × width, marginal teeth 2–4 mm long, often more than 25 either side; fruiting perianth tapering to base, ovoid or obovoid, moderately laterally flattened with distinct marginal rim or wing. — Japan; South Korea; southern and south-eastern China.......................... a. var. sieboldiana

Figures

Map 34 Distribution of Boehmeria sieboldiana Blume var. sieboldiana (●) and B. sieboldiana Blume var. fuzhouensis (W.T.Wang) Friis & Wilmot-Dear (Ê).

Fig. 33 a–l: Boehmeria sieboldiana Blume var. sieboldiana. a. Habit of stem with inflorescence-bearing axes; b. large leaf from basal part of stem; c. small leaf from upper part of stem (same plant); d, e. leaves from different plants; f. leaf, detail of adaxial surface; g. leaf, detail of abaxial surface; h. detail of stem and stipule; i. detail of male inflorescence-bearing axis with two flower-clusters (inflorescences); j. male bud; k. detail of female inflorescence-bearing axis with three flower-clusters (inflorescences); l. fruiting perianth. — m, n: Boehmeria sieboldiana var. fuzhouensis (W.T.Wang) Friis & Wilmot-Dear. m. Leaf; n. fruiting perianth (a–c, f–h: Furuse 45347; d: Wilford 547; e: Mizushima 939; i–k: Furuse 3790; l: Fosberg 37912; m, n: Chung 2798; all K). — Scale bars: a–e, m = 2 cm; f -i, k = 2 mm; j, l, n = 1 mm.