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Article from Bean's Trees and Shrubs Hardy in the British Isles
'Rhododendron augustinii' from the website Trees and Shrubs Online (treesandshrubsonline.
Shrub, to 10 m; young shoots scaly and usually pilose. Leaves (4–)5–10(-ll) × 1.8–3(–4) cm, narrowly elliptic to elliptic, apex acute to acuminate, upper surface glabrous or with a few hairs overlying the midrib, lower surface sparsely covered with distant golden to brown scales, midrib pilose, the hairs sometimes extending along the petioles. Flowers (2–)3(–5), in a loose terminal inflorescence; calyx disc-like or with lobes to 3 mm, puberulent and often ciliate; corolla blue to purple, or white, with greenish or brown spots, zygomorphic, open-funnel-campanulate, 28–40 mm, outer surface with tube sometimes scaly and/or pilose; stamens 10; ovary scaly, apex pilose, impressed below the declinate style. Flowering April-May. Royal Horticultural Society (1997)
Distribution China SE Tibet, N Yunnan, Sichuan, Hubei
Habitat 1,300–4,000 m
RHS Hardiness Rating H4
Conservation status Least concern (LC)
An evergreen shrub from 4 to 10 ft high, of bushy habit, but sometimes up to 25 ft high in the wild; shoots hairy the first and second years, scaly the first. Leaves oblong-lanceolate, 11⁄2 to 4 in. long, 1⁄2 to 1 in. wide, tapering to a fine point, tapered or rounded at the base, upper surface dark green, minutely wrinkled, and covered with fine down, undersurface scaly, and with pale bristle-like hairs on the midrib; stalk up to 1⁄4 in. long, hairy like the midrib. Flowers in May in clusters of three or four. Calyx usually very small. Corolla 21⁄2 in. across, broadly funnel-shaped, wavy at the margins, varying in colour from white to pink, purplish pink, and bluish, with yellow, olive-green, or brownish spots on the uppermost lobes. Stamens ten, reddish brown, hairy near but not at the base. Ovary scaly; style downy at the base or glabrous. Bot. Mag., t. 8497 and n.s., t. 79. (s. Triflorum ss. Augustinii)
Native of Central and W. China; discovered by Augustine Henry near Patung, Hupeh, in 1886. It first flowered in Europe in Maurice de Vilmorin’s collection at Les Barres, raised from seed sent by the missionary Farges; the plants had pale purple to white flowers. To Britain it was introduced by Wilson, who in 1900 collected a large quantity of seed near Changyang, Hupeh. More was sent by him from other parts of the province and from Szechwan during his expeditions for the Arnold Arboretum. For the Forrest introduction see below under var. chasmanthum.
According to Wilson, R. augustinii is a very common species in Hupeh and ranges far into Szechwan. ‘It is’, he wrote, ‘partial to the margins of woods but is happiest in open rocky situations where it is fully exposed to the sun.’ It is exceedingly variable in the colouring of the flowers. According to Wilson, the most common shades in the wild are pale purple to rose-purple. But near-blue forms also occur and by selection, and by crossing the best-coloured plants, these forms have come to predominate in the great rhododendron gardens, of which they are now one of the chief glories. But these near-blue plants are really a race of cultivars and are not representative of the species as a whole. It has been said that the bluer the flower the more tender the plant, but this may not be true of garden-raised seedlings. Some of the paler shades are just as beautiful, though they may not look so impressive on the show-bench. R. augustinii is not a species for gardens subject to spring frosts and is inclined to be shy-flowering in cool gardens.
Plants originally grown under the name R. chasmanthum, now included in R. augustinii, were raised from seeds collected by Forrest and by Rock in various parts of N.W. Yunnan. There is really no significant botanical difference between these southern forms and the type, but Davidian has pointed out that they usually have more flowers per truss (up to six), and the lobes of the corollas tend to be reflexed. These can still be distinguished as var. chasmanthum (Diels) Davidian. Some at least of the Forrest introductions flower somewhat later than the Wilson forms. This is true, for example, of the batch raised at Exbury from F.21470. A selection from these received an Award of Merit when shown by Lionel de Rothschild on June 3, 1930, and a First Class Certificate on June 7, 1932, so the flowering time of this form is about three weeks later than is normal for R. augustinii.
There is a form of R. augustinii with red flowers, raised from Forrest 25914, collected near Wei-hsi, which has been named var. rubrum Davidian. It flowers earlier than normal, in late March or early April.
The synonyms should be deleted; see subsp. chasmanthum below.
subsp. chasmanthum (Diels) Cullen R. chasmanthum Diels; R. augustinii var. chasmanthum (Diels) Davidian; R. chasmanthoides Balf. f. & Forr. – The following differential characters are given by Dr Cullen: indumentum of midrib beneath extending to the underside of the petiole (not so in subsp. augustinii); upper leaf-surface glabrous or with hairs on midrib only (fine bristly hairs on all veins above in subsp. augustinii); corolla without scales on the outside (scaly in subsp. augustinii).
The horticultural characters of this subspecies are mentioned on page 603.
† subsp. hardyi (Davidian) Cullen R. hardyi Davidian – This was described by Mr Davidian in 1974. Dr Rock collected the type-specimen in 1932 and introduced this subspecies in 1949, during his last expedition to China. It is fairly near to subsp. chasmanthum, but the flowers are white and the leaves deciduous. Native of northwestern Yunnan.
subsp. rubrum (Davidian) Cullen R. augustinii var. rubrum Davidian; R. bergii Davidian – This was mentioned at the bottom of page 603. The flowers are not really red, but a reddish shade of purple. Possibly a natural hybrid (Rev. 1., p. 73).
Dr Cullen points out that the type of R. vilmorinianum Balf.f. (not mentioned in the main work) is R. augustinii subsp. augustinii, but plants cultivated under the name are probably a natural hybrid between R. augustinii and R. yunnanense (Rev. 1., p. 73).
R. vilmorinianum Balf.f.
Leaves evergreen, upper surface with hairs overlying the veins, lower surface with indumentum extending along petioles, consisting of filiform acicular hairs; corolla blue or lavender, tube scaly
Distribution China (C & E Sichuan, Hubei).
Taxonomic note (incl. R. vilmorinianum Balf.f.)
R. hirsuticostatum Hand.-Mazz.
Leaves evergreen, upper surface glabrous or hairs restricted to midrib, lower surface with indumentum hardly extending along petioles; corolla blue or lavender, often relatively pale, tube lacking scales usually pilose.
Distribution China (SE Tibet, N Yunnan, W Sichuan).
Taxonomic note (incl. R. hirsuticostatum Hand.-Mazz.)
R. hardyi Davidian
Leaves deciduous, corolla white.
Distribution China (NW Yunnan).
Awards AM 1926 (Dame Alice Godman, Horsham); flowers lilac-mauve with greenish dots. AM 1930 and FCC 1932 (L. de Rothschild, Exbury) to var. chasmanthum; flowers bluish purple, with ochraceous spots.
Taxonomic note (R. hardyi Davidian)
This is a variable species; of the four subspecies recognized above, subsp. augustinii is only poorly differentiated from subsp. chasmanthum. The leaf indumentum will distinguish this species from all but R. trichanthum.
R. bergii Davidian
Leaves evergreen; petioles with hairs of two kinds, filiform-acicular as well as loriform; corolla reddish purple.
Distribution China (NW Yunnan).
Awards AM 1978 (R.N.S. Clarke, Borde Hill, Sussex) to a clone R. bergii ‘Papillon’; flowers red-purple, paler at rim, with darker bars on reverse, spotted.
Taxonomic note (R. augustinii Hemsl. var. rubrum Davidian & incl. R. bergii Davidian)