Clematis
Clematis L.
Clematis is a genus with ca. 300 species in temperate regions of the world (Xie & al. 2011). The genus is particularly rich in China where 147 are known, 93 of them endemic (Wang & Bartholomew 2001). A single species is native in Belgium, C. vitalba L. (Lambinon & Verloove 2012).
Clematis is extremely diverse and has been divided in several smaller genera. However, molecular data seem to support a broad generic concept (Xie & al. 2011). Also, infrageneric classifications based on morphology does not seem to be supported. Further genetic studies have shown that Clematis is in fact very closely related with Anemone (Lehtonen & al. 2016), especially if the latter is accepted in a broad sense (i.e., including, among others, Hepatica and Pulsatilla). However, pending further evidence, Clematis is here treated in its traditional sense.
The genus is very popular in horticultural and many species are valued as ornamentals. Useful accounts with identification keys for Clematis in cultivation in Europe are provided by, for instance, Brandenburg (1989), Roloff & Bärtels (2006) and Jäger & al. (2008). More than 50 species are upheld by Brandenburg l.c. Their recognition, however, is often a difficult matter. Hybrids and cultivars are widespread in cultivation. In some cases, especially for large-flowered hybrids, plants can only be assigned to cultivar-groups (Roloff & Bärtels l.c., Brandenburg l.c.). Many of the cultivated taxa (including several of the more popular hybrids!) freely reproduce from seed and are regularly observed as escapes, sometimes even without parental plants growing nearby. In the absence of flowers such saplings are hard to identify. Therefore, in addition to the taxa included in this account several others probably also occur in the wild but their correct identity should be assessed.
Native Clematis vitalba has considerably enlarged its distribution area in Belgium in the past decades and now occurs in regions where it is not originally native. It is not impossible that some of these records refer to cultivars, hybrids or even different, related species. The Vitalba Group in horticulture includes, in addition to C. vitalba, also C. ligusticifolia Torrey & A. Gray, C. potaninii Max. and C. virginiana L. (Donald 2015).
A useful, copiously illustrated account for the genus in Germany (wild as well is horticulture) is available here: http://www.blumeninschwaben.de/Zweikeimblaettrige/Hahnenfuss/waldrebe.htm. An overview of all species and cultivars available in horticulture is provided by RHS at: https://www.rhs.org.uk/plants/plantsmanship/plant-registration/Clematis-....
Numerous societies offer information on Clematis in cultivation. Links to some of the more important follow here under:
American Clematis Society: https://secure.clematisqueen.com/node
Clematis on the Web: http://www.clematis.hull.ac.uk/index.cfm
International Clematis Society: http://www.clematisinternational.com/
British Clematis Society: http://www.britishclematis.org.uk/
1 Stem erect, not climbing === 2
Stem climbing === 3
2 Leaves entire. Sepals blue. Flowers usually solitary and terminal, nodding === Clematis integrifolia
Leaves once pinnate, with 5-7 leaflets. Sepals white. Flowers numerous in axillary, erect panicles === C. recta
3 Sepals yellow === C. tangutica
Sepals bluish, white or purplish === 4
4 Leaves predominantly ternate (sometimes the upper undivided) === 5
Leaves pinnate === 6
5 Sepals white or pink. Flowers 4-6 cm across, on previous year’s shoots === C. montana
Sepals dark violet-blue or white. Flowers 10-14 cm across, on current year’s shoots === C. xjackmanii
6 Sepals blue to purple. Beak of achene glabrous in fruit. Flowers solitary or up to three === C. viticella
Sepals creamy white. Beak of achene plumose in fruit. Flowers in multi-flowered panicles === 7
7 Sepals hairy on both surfaces. Leaves once pinnate (native) === C. vitalba
Sepals hairy only on lower surface. Leaves twice pinnate === C. flammula
Literature:
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