| Photinia | |
|---|---|
| Photinia × fraseri | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Rosales |
| Family: | Rosaceae |
| Subfamily: | Amygdaloideae |
| Tribe: | Maleae |
| Subtribe: | Malinae |
| Genus: | Photinia Lindl. |
| Species | |
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Photinia ( /fɵˈtɪniə/)[1] is a genus of about 40-60 species of small trees and large shrubs in the Rosaceae family. As interpreted here, they are restricted to warm temperate Asia, from the Himalaya east to Japan and south to India and Thailand, but some botanists also include the closely related North American species Heteromeles arbutifolia in Photinia as Photinia arbutifolia. The genus Stranvaesia is so similar in morphology to Photinia that its species have sometimes been included within it,[2][3] but recent molecular data[4] indicate that the two genera are not related. The genus Aronia has been included in Photinia in some classifications,[5] but recent molecular data confirm that these genera are not closely related.[4] Other close relatives include the firethorns (Pyracantha), cotoneasters (Cotoneaster) and hawthorns (Crataegus). The scientific name Photinia is widely used as the common name. Another name sometimes used is "Christmas berry", but this name is a source of confusion, since it is commonly applied to plants in several genera including Heteromeles, Lycium, Schinus, and Ruscus.
The name Photinia continies to be used for several species of small trees in the mountains of Mexico and Central America. These had formerly been included in the genus Photinia.[6]
Photinias typically grow from 3–15 m tall, with a usually irregular crown of angular branches; the branches are often (not always) thorny. The leaves are alternate, entire or finely toothed, varying between species from 3–15 cm in length and 1.5–5 cm wide; the majority of species are evergreen but several are deciduous. The flowers are produced in early summer in dense terminal corymbs; each flower is 5–10 mm diameter, with five rounded white petals; they have a mild, hawthorn-like scent. The fruit is a small pome, 4–12 mm across, bright red and berry-like, produced large quantities, maturing in the fall and often persisting well into the winter. The fruit are consumed by birds, including thrushes, waxwings and starlings; the seeds are dispersed in their droppings. Photinia species are sometimes used as food plants by the larvae of some Lepidoptera species including Common Emerald, Feathered Thorn and Setaceous Hebrew Character.
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A number of species have been moved to the separate genus Stranvaesia including P. amphidoxa, P. davidiana, P. nussia, and P. tomentosa.
Photinias are very popular ornamental shrubs, grown for their fruit and foliage. Numerous hybrids and cultivars are available; several of the cultivars are selected for their strikingly bright red young leaves in spring and summer. The most widely planted are:
Some varieties of Photinia are toxic due to the presence of cyanogenic glycosides in the vacuoles of foliage and fruit cells.[7] When the leaves are chewed these compounds are released and are rapidly converted to hydrogen cyanide (HCN) which blocks cellular respiration. The amount of HCN produced varies considerably between taxa, and is in general greatest in young leaves.[8] Ruminants are particularly affected by cyanogenic glycosides because the first stage of their digestive system (the rumen) provides better conditions for liberating HCN than the stomachs of monogastric vertebrates.[9]