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Dan Crowley (2020)
Crowley, D. (2020), 'Acer divergens' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub or tree to 10 m in the wild. Bark pale brown to yellowish-grey. Branchlets glabrous, turning grey to brown and woody by the end of the first year. Buds ovoid, usually with 6 pairs of imbricate scales. Leaves broadly pentagonal in outline, base subcordate to truncate, 3– to 5-lobed, 2–3.5 × 3–5 (–8) cm, margins entire, lobes triangular to ovate, apically obtuse, upper surface mid-green, lower surface pale green; petiole 2–3 cm long, slender, glabrous, exuding milky sap when broken; autumn colour yellow. Inflorescence, corymbose, erect, glabrous, few flowered. Flowers yellowish-green, 5-merous, usually andromonoecious. Samaras 1.2–2.2 cm long, wings spreading nearly horizontally; nutlets flattened. Flowering from April to May, appearing with unfolding leaves, fruiting from September to October. (Yaltirik 1967; van Gelderen et al. 1994; le Hardÿ de Beaulieu 2003).
Distribution Turkey Artvin, Erzurum
Habitat Dry and sunny slopes along watercourses between 400 and 1500 m asl.
USDA Hardiness Zone 5-6
RHS Hardiness Rating H6
Conservation status Vulnerable (VU)
Taxonomic note This species is treated as a subsp. of Acer cappadocicum by van Gelderen et al. (1994). The treatment at specific rank follows Yaltirik (1967), who also includes two varieties within it, the nominate variety, with 5-lobed leaves with truncate bases, and var. trilobum Yalt, with 3-lobed leaves with rounded bases. It is part of the A. cappadocicum complex, along with that species (including subsp. sinicum), A. lobelii and A. shenkanense.
The rarest member of the Acer cappadocicum complex in cultivation, A. divergens was introduced to Kew in 1923 Bean (1976), remaining largely restricted to specialist collections ever since. Morphologically it appears quite distinct from A. cappadocicum and other members of the complex, possessing far smaller leaves and, significantly, branchlets that turn brown and woody by the end of the first year’s growth. In this respect it appears more allied to A. pictum than to A. cappadocicum, though its relationship to A. campestre should also be investigated. As noted elsewhere, a comprehensive molecular study on the section is required. Endemic to northeastern Turkey, its range does overlap with that of Acer cappadocicum subsp. cappadocicum, and though van Gelderen et al. (1994) suggest that the two merge at their extremes, hybridisation in the wild is not reported by authors of the Turkish flora.
In cultivation, as in the wild, the species takes a multistemmed form. Single-stemmed trees with untypically large leaves grown in collections should be observed with scepticism, as hybridisation with any number of its relatives in the section is quite possible. Known origin material in cultivation is somewhat scarce, though wild origin plants, fitting the typical variety, grow at Chelsea Physic Garden and Howick Hall. Perhaps unsurprisingly, the species appears happier in the Chelsea climate than in Northumberland. Plants of var. trilobum have not been observed in collections.