It is a deciduous shrub or small tree that most often grows to 1–8 metres (3–26 feet), rarely to 10 m or 33 ft, in height. Its growth form spans from suckering and forming colonies to clumped. The leaves are oval to nearly circular, 2–5 centimetres (3⁄4–2 inches) long and 1–4.5 cm (1⁄2–1+3⁄4 in) broad, on a 0.5–2 cm (1⁄4–3⁄4 in) leaf stem, with margins toothed mostly above the middle.

As with all species in the genus Amelanchier, the flowers are white, with five quite separate petals and five sepals. In A. alnifolia, they are about 2.5–5 cm (1–2 in) across, with 20 stamens and five styles, appearing on short racemes of 3–20, somewhat crowded together, blooming from April to July.

The fruit is a small purple pome 5–15 mm (3⁄16–19⁄32 in) in diameter, ripening in early summer in the coastal areas and late summer further inland. Resembling blueberries, it has a waxy bloom. Serviceberry species can be relatively difficult to distinguish.

Chemistry

Also similar in composition to blueberries, saskatoons have total polyphenol content of 452 milligrams per 100 grams (average of 'Smoky' and 'Northline' cultivars), flavonols (61 mg) and anthocyanins (178 mg), although others have found the phenolic values to be either lower in the 'Smoky' cultivar or higher. Quercetin, cyanidin, delphinidin, pelargonidin, petunidin, peonidin, and malvidin were present in saskatoon berries.