Family: Rosaceae
Mountain-Ash
Key to Wisconsin Sorbus
- 1a.Hypanthium, sepals, and winter buds densely white-pubescent; leaflets pubescent abaxially. S. aucuparia
- 1b.Hypanthium, sepals, and winter buds glabrous or sparsely pubescent; leaflets glabrous or glabrate abaxially. 2
- 2a.Lateral leaflets 3.4–5 times as along as wide, gradually tapered or acuminate at the apex, usually completely glabrous at maturity; petals 2.5–3 mm long; pedicels and inflorescence branches glabrous or glabrate; mature pomes 4–7 mm in diameter. S. americana
- 2b.Lateral leaflets 2.4–3 times as long as wide, abruptly acute to obtuse at the apex, often with some pubescence along the midrib abaxially; petals 3–4.5 mm long; pedicels and inflorescence branches somewhat hairy; mature pomes (6–) 8–10 mm in diameter. S. decora
Our two native species of mountain-ash have become rarer in recent decades, due in part to increased deer browsing and forest succession. They are most often seen as seedlings or mature trees (infrequently as saplings) with the latter usually on cliffs or bluffs and other areas inaccessible to deer. They are both still relatively common on the Apostle Islands but have declined due to forest succession on islands without deer populations; they are mainly found in forest gaps or on shorelines. Their ecology and status are in dire need of being studied.
