Also known as Oakleaf Mountain Ash, is a cross between the European ashes Sorbus aria and Sorbus aucuparia, or possibly Sorbus rupicola and Sorbus aucuparia. It is introduced in the U.S. It is a deciduous small tree growing to 6 m (20 ft) tall in an oval, pyramidal shape, and about two-thirds as wide. The leaves are alternate, pinnately compound and resemble the leaves of the English oak. The leaflets are lobed toward their ends, matte dark green above, whitish and fuzzy below, 7.6-8.9 cm (3-3.5 in) long, 5-6.5 cm (2-2.5 in) wide. The petiole is 1.3-2.5 cm (.5-1 in) long. In late spring, perfect white 5-lobed flowers bloom that are .8 cm (.33 in) across and are borne on short, sturdy pedicels in corymbs (2-5 in) wide. The round orange-red pomes 1.3 cm (.5 in) in diameter are displayed in showy, dense clusters in early and late fall. Fruits have 1 or 2 viable seeds.
This project was supported in part by NSF Grant IIS-03-25867 (ITR: An Electronic Field Guide: Plant Exploration and Discovery in the 21st Century) and by the Washington Biologists' Field Club.
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