Photinia
Bot. Reg. 6: plate 491. 1820.
Shrubs or trees, 10–120 dm. Stems 1–15+, erect; bark gray; short shoots absent; unarmed; glabrous. Leaves persistent or deciduous, cauline, simple; stipules deciduous, free, usually subulate, margins dentate or entire; petiole present; blade oblong to elliptic or elliptic-obovate, 3–20 cm, coriaceous or herbaceous, margins flat, serrate to serrulate, rarely entire, venation pinnate, surfaces glabrous at least at maturity. Inflorescences terminal, erect or pendulous in fruit, 150–300-flowered, corymbose (compound-corymboid) or subumbellate [compound-racemose], glabrous or glabrate; bracts present; bracteoles present. Pedicels present. Flowers: perianth and androecium perigynous, 6–12[–15] mm diam.; hypanthium cupulate to campanulate or cylindric, 1–2 mm, usually glabrous; sepals 5, incurved, triangular; petals 5, white, oblong to elliptic, obovate, or orbiculate to suborbiculate, base clawed; stamens (16–)20(–25), ± as long as or slightly shorter than petals; carpels (1 or)2–5, connate, adnate to proximal 1/2–1/3 of hypanthium, free apically, glabrous or apically pilose, styles [1 or]2–4[or 5], terminal, distinct or ± basally connate, stigmas truncate or capitate; ovules 1 or 2. Fruits pomes, red or black, globose to ovoid or ellipsoid, sometimes apically depressed, 4–8[–12] mm, usually glabrous; somewhat fleshy; carpels capped by hard-shelled dome that rises above hypanthium; hypanthium persistent; sepals persistent, spreading (adnate to hypanthium); carpels cartilaginous; styles deciduous. Seeds (1 or)2 per carpel. x = 17.
Distribution
Introduced; Mexico, Central America, Asia, introduced also in Europe, Pacific Islands (Hawaii, New Zealand), Australia.
Discussion
Species 40–60 (4 in the flora).
Photinia is widely introduced in cultivation and naturalizing, at least in the continental United States. Species are native mostly to warm temperate Asia, from the Himalayas east to Japan and south to India and Thailand. Molecular data suggest that Heteromeles originated through hybridization, with a species of Photinia as pollen parent (Guo W. et al. 2011).
Five species from Mexico and Central America were included within Photinia by J. B. Phipps (1992) and molecular evidence corroborates their placement there (Guo W. et al. 2011).
The Asian Stranvaesia has sometimes been treated as distinct from Photinia, but botanists have noted the apparent artificiality of a primary character used to differentiate the two genera, namely an endocarp dehiscent in Stranvaesia, indehiscent in Photinia (C. Kalkman 1973; J. B. Phipps et al. 1991b; K. R. Robertson et al. 1991; J. R. Rohrer et al. 1991, 1994). Kalkman observed that the putative dehiscence of Stranvaesia carpels is an artifact of specimen preparation. Rohrer et al. (1991, 1994) found that Photinia and Stranvaesia do not differ in connation of the carpels or in the adnation of the carpels to the hypanthium. Molecular phylogenetic analyses (Guo W. et al. 2011) show that the Stranvaesia species have arisen within the cladistic topology of Photinia.
The primarily eastern North American genus Aronia (for example, A. floribunda, A. melanocarpa) has been included in Photinia in some classifications (K. R. Robertson et al. 1991) but is here treated as distinct.
Many species of Photinia are ornamental trees and shrubs with large lustrous leaves and masses of white flowers in the spring followed by red fruits in the fall. The flowers last about two weeks and commonly have an unpleasant smell. The wood is hard and heavy and has been used for furniture and small articles such as axe handles.
Photinias have been widely and abundantly planted for hedging in the southeastern United States. The rapid spread since about the mid 1980s of a fungal leaf spot, Entomosporium maculatum, has been lethal to many such hedges. Photinia ×fraseri ('red tip'; see under 2. P. serratifolia) and P. glabra are severely affected; P. serratifolia is said to be partially resistant.
Selected References
None.
Key
| 1 | Leaf margins entire. | Photinia davidiana |
| 1 | Leaf margins usually serrate or crenate-serrulate | > 2 |
| 2 | Leaves deciduous, blades herbaceous; inflorescences 3–6 cm diam.; pedicels with warty lenticels. | Photinia villosa |
| 2 | Leaves persistent, blades coriaceous; inflorescences 4–18 cm diam.; pedicels without lenticels | > 3 |
| 3 | Leaf blades 5–9 cm, lateral veins 10–15(–18) pairs, margins crenate-serrulate; inflorescences 4–10 cm diam. | Photinia glabra |
| 3 | Leaf blades (6–)9–20 cm, lateral veins 20–30 pairs, margins sharply serrate to inconspicuously toothed or entire; inflorescences 10–18 cm diam. | Photinia serratifolia |