Shrubs 1–9 m tall, bushy habit. Branchlets quadrangular to subterete, stellate tomentose to almost glabrous; long branchlets delicate, declinate on apical parts. Leaves alternate; leaf blade short, stellate tomentose on both surfaces or upper surface glabrescent, margin entire or undulately dentate. Leaves on long vegetative branchlets with short petiole 1–2 mm; leaf blade very narrowly elliptic to almost linear, 3–10 × 0.2–1.3 cm, base cuneate, apex acuminate to obtuse. Leaves on floriferous branchlets somewhat different, shortly petiolate to subsessile; leaf blade 5–15 × 2–10 mm, base cuneate to decurrent, apex rounded to obtuse. Inflorescences congested, only on short lateral branchlets, paniculate cymes or glomerules, 1–4.5 × 1–3 cm. Flowers fragrant. Calyx campanulate, 2.5–4 mm, outside stellate tomentose and with some glandular hairs, inside a few minute glandular hairs on upper half; lobes triangular, 0.5–1.7 mm. Corolla lilac, violet, or purple, occasionally white, with an orange throat, tube 6–10 × 1.2–1.8 mm; lobes suborbicular to broadly ovate, 1.2–3 × 1.2–3 mm, outside sparsely pubescent, some stellate hairs to almost glabrous, inside with pilose zone from in lower half from 0.5–1 mm above the base. Stamens inserted at middle of corolla tube; anthers seesile or subsessile, oblong, 1–1.8 mm. Pistil included, glabrous, 2.5–4 mm long; ovary ovoid to subovoid, 1–2 mm, laterally comporessed. Style c. 1 mm; stigma large, clavate. Capsule ellipsoid, c. 5 × 2 mm, glabrous. Seeds pale brown, narrowly oblong, 1.5–2 mm, winged all around. Flowering spring to early summer. (Leeuwenberg 1979; Li & Leeuwenberg 1996).
Distribution China Gansu, Hebei, Henan, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, Sichuan, Xizang
Habitat In thickets, along river banks or dry river beds, high up in mountains, 1500–4000 m asl.
USDA Hardiness Zone 5-9
RHS Hardiness Rating H6
Awards RHS AGM
Conservation status Not evaluated (NE)
Taxonomic note Buddleja tsetangensis was sunk as a synonym of B. alternifolia by Leeuwenberg (1979), whose taxonomy of old world Buddleja is followed here. However some authorities such as Plants of the World Online maintain it as a distinct species – it has never been described at infraspecific rank. Some nomenclatural distinction is of value to horticulture and so we discuss it below under the heading ‘tsetangensis type’.
Buddleja alternifolia was described and named by Maximowicz in 1880, and introduced into cultivation by William Purdom and Reginald Farrer around 1915. Unlike nearly every other member of the genus B. alternifolia has alternate rather than opposite leaves, the feature for which it is named. The leaves are uncharacteristically small and narrow, and the species is fully deciduous in most situations. It forms a graceful arching shrub or small tree. The flower-bearing branchlets are pendulous and their leaves slightly smaller than average; in mature specimens these form a cascade of flowers that give the plant its common name of Fountain Buddleja. A well-formed, established plant in full flower is a beautiful sight. The inflorescences are spirally arranged in congested cymes along the branchlets, and the corolla is generally a pinkish lilac. The flowers appear in late spring or very early summer (April–June in the UK, depending on conditions).
B. alternifolia is generally considered to be very hardy, but Tom Christian notes that an established shrub was killed outright in Highland Perthshire, Scotland, in the 2009–2010 winter when temperatures dipped below –15°C during a period of sustained sub-zero temperatures (T. Christian pers. comm. 2021). It is tolerant of most soil types, although a rich loamy soil with good drainage is preferred, and grows best a sunny position. A popular garden shrub, it is non-invasive and has a relatively low seed set. As a species bearing its flowers on wood made during the previous summer, it should not be spring-pruned; any necessary pruning should be immdiately after flowering, which will initiate strong vegetative growth.
B. alternifolia is relatively common in cultivation, only B. davidii and B. globosa are more widely known. It can reach the proportions of a small tree, but can also be pruned into a standard and grown as a free-standing shrub, or trained over arches and pergolas, or against a wall (Bean 1988; Stuart 2006).
RHS Hardiness Rating: H4
Named for its silvery leaves, ‘Argentea’ is identical to the species except for the increased tomentum on both leaf surfaces; the flowers are also darker – mauve rather than lilac. Possibly less vigorous and less forgiving of adverse conditions than typical forms of the species, it is nonetheless easy to grow in any reasonable well-drained soil. It is considered by some one of the finest cultivars of any Buddleja (Stuart 2006).
Synonyms / alternative names
Buddleja alternifolia UNIQUE
A seedling of B. alternifolia selected by Peter Moore of the Longstock Nursery, Hampshire, UK in 2007. Generally, the plant resembles the species in most respects, having narrow alternate foliage and being fully deciduous. The individual flowers are mauve and slightly altered in shape, however, these flowers are sterile; this probably accounts for the ability of UNIQUE to re-bloom repeatedly throughout the summer on new shoots, a habit very unlike the species which flowers once in the late spring on the previous year’s growth (P. Moore, pers.comm.).
Synonyms / alternative names
Buddleja tsetangensis Marquand
The type specimen of Buddleja tsetangensis (Marquand 1930) was collected at high altitude (3600 m) in the Tsang-Po valley by Kingdon-Ward in 1924 (KW 5616) (Marquand 1929). This was originally considered a separate species but was subsequently sunk as a synonym of B. alternifolia in the last major revision of African and Asian members of the genus (Leeuwenberg 1979) and this taxonomy is followed here. Leeuwenberg did not consider the distinguishing features – a lax but congested growth habit and a white rather than lilac corolla – sufficient to merit species status, and so he included this taxon within B. alternifolia based on its very similar flower morphology (Leeuwenberg 1979). It is worth noting however that the species is still accepted (September 2021) in Plants of the World Online, but without comment or reference to Leeuwenberg’s lumping. Certainly in the eyes of a horticulturist, plants of this type are quite distinct from B. alternifolia.
More recently, a specimen has been collected from the same location by Keith Rushforth and introduced into cultivation under KR 4881; this plant forms a small tree with a lax but congested habit. The foliage is always alternate and silver-grey; the leaf-blade is narrow with repand-dendate margins. The flowers are white and appear on the previous year’s growth in the spring. Although initially identified as B. × wardii Marquand (a naturally occuring hybrid of B. alternifolia and B. crispa, and sympatric with B. tsetangensis), the current author believes this plant to be B. alternifolia of the B. tsetangensis type. The flower morphology of this collection is identical to B. alternifolia and unlike that reported for B. × wardii; most notably KR 4881 lacks the tomentose ovary reported for B. × wardii (Marquand 1930).