The rowans or mountain-ashes are shrubs or trees in the genus Sorbus of the rose family, Rosaceae. They are native throughout the cool temperate regions of the Northern Hemisphere, with the highest species diversity in the Himalaya, southern Tibet and parts of western China, where numerous apomictic microspecies occur. The name rowan was originally applied to the species Sorbus aucuparia and is also used for other species in Sorbus subgenus Sorbus.
Sorbus aucuparia, commonly called rowan and mountain-ash, is a species of deciduous tree or shrub in the rose family. It is a highly variable species, and botanists have used different definitions of the species to include or exclude trees native to certain areas; a recent definition includes trees native to most of Europe and parts of Asia, as well as northern Africa. The range extends from Madeira, the British Isles and Iceland to Russia and northern China. Unlike many plants with similar distributions, it is not native to Japan.
Sorbus is a genus of over 100 species of trees and shrubs in the rose family, Rosaceae. Species of Sorbus (s.l.) are commonly known as whitebeam, rowan (mountain-ash) and service tree. The exact number of species is disputed depending on the circumscription of the genus, and also due to the number of apomictic microspecies, which some treat as distinct species, but others group in a smaller number of variable species. Recent treatments classify Sorbus in a narrower sense to include only the pinnate leaved species of subgenus Sorbus, raising several of the other subgenera to generic rank.
Sorbus torminalis, with common names wild service tree, chequers, and checker tree, is a species of tree in the mountain ash or rowan genus (Sorbus) of the rose family (Rosaceae), that is native to Europe, parts of northern Africa and western Asia.
Aesculus californica, commonly known as the California buckeye or California horse-chestnut, is a species of buckeye native to California and southwestern Oregon.
Paeonia californica is a perennial herbaceous plant of 35–70 cm high, that retreats underground in summer, and reoccurs with the arrival of the winter rains. It has lobed leaves, elliptic (cup-shaped) drooping flowers with dark maroon-colored petals, and many yellow anthers. It flowers mostly from January to March, and later develops two to five fruits per flower. Its common name is California peony and it is sometimes also referred to as wild peony. This peony is an endemic of southwestern California (USA), where it is not rare, and northernmost Baja California (Mexico). It grows on dry hillsides in the coastal sage scrub and chaparral communities of the coastal mountains of Southern and Central California, often as an understory plant.
The Arran whitebeams are species of whitebeam endemic to the island of Arran, Ayrshire, Scotland.
Regional floras typically contain complete dichotomous keys for identification of trees and other plants to species. The following guide originates from Our Native Trees and How to Identify Them by Harriet L. Keeler and applies to some flowering trees which are indigenous to the region extending from the Atlantic Ocean to the Rocky Mountains and from Canada to the northern boundaries of the southern states, together with a few well-known and naturalized foreign trees. This guide excludes conifers and is not an exhaustive list of all trees known to occur in the region.
The tree species Sorbus americana is commonly known as the American mountain-ash. It is a deciduous perennial tree, native to eastern North America.
Sorbus sitchensis, also known as western mountain ash and Sitka mountain-ash, is a small shrub of northwestern North America.
Sorbus glabrescens is a species of rowan native to Yunnan in China.
Sorbus oligodonta, the kite-leaf rowan, is a species of rowan native to northern Yunnan, southeastern Tibet, and western Sichuan in China as well as to Myanmar.
Sorbus × hybrida, the oakleaf mountain ash, Swedish service-tree or Finnish whitebeam, is a hybrid species of whitebeam native to Norway, eastern Sweden, southwestern Finland, and locally in Latvia.
Sorbus alnifolia, also called alder-leafed whitebeam, Korean whitebeam, or Korean mountain ash, Chinese: 水榆花楸; pinyin: shui yu hua qiu; lit. 'water elm rowan', is a species of whitebeam native to eastern Asia in eastern and northern China, Taiwan, Korea and Japan.
Sorbus hupehensis is a species of rowan native to central and western China.
Sorbus sargentiana, Sargent's rowan is a species of flowering plant in the family Rosaceae, native to southwestern Sichuan and northern Yunnan in China, where it grows at altitudes of 2,000–3,200 m (6,560–10,500 ft).
Sorbus decora, commonly known as the northern mountain ash, showy mountain-ash, or dogberry, is a deciduous shrub or very small tree native to northeastern North America. It occurs throughout the Laurentian Mixed Forest Province, the New England-Acadian forest region, and the eastern Canadian boreal forests.
Sorbus vilmorinii, the Vilmorin's rowan or Vilmorin's mountain ash, is a species of flowering plant in the family Rosaceae, native to Sichuan, Tibet and Yunnan in China.
Sorbus scopulina is a species of rowan that is native to western North America, primarily in the Rocky Mountains. The common name of this species is often given as Greene's mountain-ash, and is so named in honor of American botanist Edward Lee Greene. Throughout the Cascade Mountains and the Pacific Northwest portions of this rowan's habitat, it is commonly called Cascade mountain-ash, sometimes listed as Sorbus scopulina var. cascadensis.
S. californica fruits (left) are apple-shaped; S. aucuparia fruits for comparison are conical at the stem end
The individual leaflets are toothed almost from base to apex
