Mountain Ash

Sorbus poteriifolia

Rosaceae · broadleaf deciduous shrub · introduced

Last updated May 11, 2026

Quick Facts

Height

9 ft

Light

Full Sun to Part Shade

Hardiness

Zone Zones 3a–8b

Fall Color

Red

Origin

stony slopes

Cytospora CankerHigh

Spring Canker Activation

Fire BlightHigh

Bloom Infection Window

Nectria CankerHigh

Spore Release (Fall & Spring Rains)

RustHigh

Aecial Stage (Alternate Host)

+ 4 more — see full disease and pest lists below

Diseases: Regionally Documented (5)

Cytospora spp. (Valsa spp., Leucostoma spp.) Cytospora Canker Erwinia amylovora Fire Blight Symptom category — not a single disease Leaf Spot Neonectria ditissima Nectria Canker Multiple genera (Melampsoridium, Thekopsora, Naohidemyces... Rust

Pests: Regionally Documented (9)

Aphidoidea Aphid Choreutis pariana Apple-and-thorn skeletonizer Ash borer Enarmonia formosana Cherry bark tortrix Leaf blister mite Pristiphora geniculata Mountain ash sawfly Pear sawfly (pear slug) Otiorhynchus spp. Root weevil Malacosoma spp. Tent caterpillar

Data Maturity

Structured Multiple sources. Expert review underway.