European Mountain Ash

Sorbus aucuparia

Rosaceae · broadleaf deciduous tree · introduced

Last updated May 24, 2026

European mountain ash is widely planted in the Puget Sound lowlands but it is a poor long-term bet. The tree is heat-intolerant and our warming summers are pushing it past its comfort zone. Stressed trees are shorter-lived (30-50 years) and more vulnerable to fire blight and cytospora canker. Mountain ash sawfly can strip the foliage in heavy years. The orange-red fruit clusters in September-October are the primary ornamental value and they are genuinely good bird food. For new plantings, consider Sitka mountain ash (Sorbus sitchensis), which is better adapted to our coastal climate. If you have an existing European mountain ash that is healthy, it is worth keeping, but plan for replacement within a few decades.

— Chris Welch, ISA Certified Arborist

Plant Profile

Size & Form

Height

40 ft

Spread

23 ft

Growth Rate

Moderate

Size at 20 yr

35 ft

Lifespan

Moderate

Site Requirements

Light

Sun to Part Shade

Soil Drainage

Well Drained

Soil pH

4.5–7.5

Water

Moderate

Drought Tolerance

Low

Hardiness

Zones 2a–8b

Ornamental Interest

Bloom Time

May

Fall Color

Yellow to reddish-purple

Origin

Europe, Asia

Cytospora CankerHigh

Peak Spore Production and Dispersal

Fire BlightHigh

Bloom Infection Window

RustHigh

Uredinial Stage (Summer)

AphidHigh

Peak Population & Dispersal

+ 2 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 Enarmonia formosana Cherry bark tortrix Pristiphora geniculata Mountain ash sawfly Pear sawfly (pear slug) Leaf blister mite Otiorhynchus spp. Root weevil Malacosoma spp. Tent caterpillar Ash borer (lilac borer)

Phenological Calendar

View full calendar (9 stages)

Stage	Typical Window	What to Look For
Bud break BBCH 07	Feb 15-Mar 15	Buds swelling and beginning to open; first green tissue visible
Leaf emergence BBCH 11	Mar 1-Apr 1	First leaves fully unfurled on new growth
Bloom start BBCH 61	May 1-May 25	First open flowers visible in dense, flattened corymbs; creamy-white, mildly fragrant; attractive to bees
Bloom end / petal fall BBCH 69	May 25-Jun 15	Last petals falling from corymbs; small green pomes forming at base of spent flowers
Fruit/seed development BBCH 71	Jun 15-Aug 31	Small green pomes enlarging in clusters (6-9 mm diam.); clusters becoming pendulous as fruit gains weight
Fruit color turning BBCH 83	Aug 15-Sep 15	Fruit turning from green to yellow-orange; indicator for pine needle scale 2nd generation egg hatch
Fruit/seed maturity BBCH 85	Sep 1-Nov 30	Fruit fully orange-red, glossy, in heavy pendulous clusters; attracts birds (waxwings, thrushes); indicator for two-spotted spider mite population decline
Fall color / leaf senescence BBCH 93	Oct 1-Nov 15	Leaves changing color; fall display beginning
Dormancy BBCH 97	Nov 15-Feb 28	Leafless; no active growth; dormant buds set

Cultivars (6)

'Cardinal Royal ('Michred')'

Vigorous, upright habit; bright red fruit in large clusters; dark green foliage with silvery underside; orange-red fall color. 30-40 ft tall, 15-20 ft wide.

Hardy to USDA Zone 2. Developed at Michigan State University. Considered the best red-fruited selection for uniform shape.

'Fastigiata'

Columnar, upright form with rigid, stout branches forming a narrow pyramid. Fruit larger than species.

Useful where narrow profile is needed. Hardy to USDA Zone 3.

'Edulis'

Leaflets larger, nearly entire margins with red-purple petioles. Fruit larger, less bitter, suitable for jams and jellies.

Selected for edible fruit quality. Also sold as 'Moravica' or 'Dulcis'.

'Asplenifolia'

Leaflets deeply divided and sharply serrated, giving a fern-like texture. Graceful appearance.

'Black Hawk'

Narrow tree habit; large orange fruit; dark green foliage. Resists sun-scald.

Introduced in the 1960s.

'Pendula'

Weeping form; branches droop. Typically top-grafted for ornamental effect.

Data Maturity

Structured Multiple sources. Expert review underway.