(incl. Stranvaesia Lindl.)
The generic limits of Photinia have long been controversial. According to Potter & al. (2007) it should be maintained as a separate genus. Others have included it in a broadly circumscribed genus Aronia (Mabberley 2008). In Potter & al. l.c. Stranvaesia – usually included in Photinia – is also reinstalled at generic level (see also Phipps 1990, Lingdi & Spongberg 2003 a, b). However, this is in discordance with more recent phylogenetic studies (Guo & al. 2011): all phylogenetic trees produced indicated that Stranvaesia should be merged into Photinia, while Pourthiaea and Aronia should be delimited as two separate genera. The separation of Stranvaesia from Photinia is also poorly supported on morphological grounds. Both genera are indeed very similar and one of the main distinguishing features (carpel dehiscence) appears to be unreliable (Lingdi & Spongberg 2003 a, b). Also, hybrids are easily produced between Photinia and Stranvaesia. A common cultivar of Photinia davidiana (cv ‘Redstar’) is believed to be such a hybrid. According to Gardner & Knees (1995) Aronia and Photinia differ on stamen number (respectively less than 25 and numerous) but this does not hold true (ca. 20 in all species concerned in both genera in the present account). The three Belgian representatives of Photinia s.l. (incl. Stranvaesia) (all non-native species) are readily told apart: Photinia s.str. counts two deciduous species with leaves with toothed margins whereas the single species of Stranvaesia is evergreen and has leaves with entire margins.
As currently circumscribed Photinia s.l. probably counts about 60-70 species (Lingdi & Spongberg 2003 a, b). These are predominantly native in East, South and Southeast Asia. Several species are cultivated as ornamentals, especially for their colorful foliage. Gardner & Knees (1995) enumerate 14 species for European gardens but only few are more or less widespread (see De Koning & al. 2000, Roloff & Bärtels 2006). The berries of Photinia are eaten by birds and hence easily dispersed. More frequent occurrences, in addition to the few known so far, are not unlikely.
A fourth species of Photinia/Stranvaesia is frequently cultivated and could have been overlooked: P. xfraseri Dress (= P. glabra (Thunb.) Maxim. x P. serratifolia (Desf.) Kalkman) (see also Dress 1961). Like Stranvaesia davidiana it is an evergreen shrub but its leaf margins have fine forward-pointing teeth. It was recently recorded as an escape in the British Isles (Wilmore 2000).
1 Evergreen. Leaves with entire margins === Photinia davidiana
Deciduous. Leaf margins toothed === 2
2 Inflorescence branches glabrous. Lower leaf surface glabrous with 8-14 veins. Leaf margin with gland-tipped teeth === P. beauverdiana
Inflorescence branches villous. Lower leaf surface persistently hairy with 5-7 veins. Leaf margins without gland-tipped teeth === P. villosa
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