About Amelanchier alnifolia (Nutt.) Nutt.
Amelanchier alnifolia (Nutt.) Nutt. is a deciduous shrub or small tree. It most often reaches 1 to 8 metres (3 to 26 feet) in height, and rarely grows as tall as 10 m (33 ft). Its growth form ranges from producing suckers to form large colonies, to growing in tight clumps. Its leaves are oval to nearly circular, measuring 2 to 5 centimetres (3⁄4 to 2 inches) long and 1 to 4.5 cm (1⁄2 to 1+3⁄4 in) wide, borne on a 0.5 to 2 cm (1⁄4 to 3⁄4 in) petiole, with toothed margins mostly only on the upper half of the leaf. Like all species in the genus Amelanchier, this species produces white flowers with five completely separate petals and five sepals. In A. alnifolia, individual flowers are around 2.5 to 5 cm (1 to 2 in) across, with 20 stamens and five styles. Flowers grow in short, somewhat crowded racemes that hold 3 to 20 flowers each, and bloom from April to July. The fruit is a small purple pome 5 to 15 mm (3⁄16 to 19⁄32 in) in diameter, which ripens in early summer and has a waxy bloom. Distinguishing different Saskatoon Amelanchier species can be relatively difficult. This plant occurs from Alaska across most of western Canada, and in the western and north-central United States. Across the northern part of its range it grows at sea level, while it can be found up to 2,600 m (8,530 ft) elevation in California and up to 3,400 m (11,200 ft) in the Rocky Mountains. It is a common shrub in forest understories and in canyons. A. alnifolia is susceptible to several diseases: cedar-apple rust, Entomosporium leaf spot, fireblight, brown rot, Cytospora canker, powdery mildew, and blackleaf. Problematic insect pests that affect this species include aphids, thrips, mites, bud moths, saskatoon sawflies, and pear slug sawflies. It also acts as a larval host plant for the pale tiger swallowtail, two-tailed swallowtail, and western tiger swallowtail butterflies. Its foliage is browsed by deer, elk, rabbits, and livestock, while its fruit is eaten by a range of wildlife including birds, squirrels, and bears. For cultivation, seedlings are planted with 4.0 to 6.1 m (13 to 20 ft) of space between rows, and 0.46 to 0.91 m (1.5 to 3 ft) of space between individual plants. A single bush can produce fruit for 30 years or more. Saskatoons are adaptable to most soil types, with the exception of poorly drained soils, heavy clay soils that lack organic matter. Shallow soils should also be avoided, especially where the water table is high or fluctuates erratically. This species has exceptional winter hardiness, but late frost as late as May can damage its blooms. It requires large amounts of sunshine for successful fruit ripening.
