European Mountain Ash
Sorbus aucuparia
Rosaceae · broadleaf deciduous tree · introduced
Last updated
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
Quick Facts
Phenological Calendar
| Stage | Typical Window |
|---|---|
| Bud break BBCH 07 | Feb 15-Mar 15 |
| Leaf emergence BBCH 11 | Mar 1-Apr 1 |
| Bloom start BBCH 61 | May 1-May 31 |
| Bloom end / petal fall BBCH 69 | May 15-Jun 15 |
| Fruit/seed development BBCH 71 | Jun 1-Aug 31 |
| Fruit/seed maturity BBCH 85 | Sep 1-Nov 30 |
| Fall color / leaf senescence BBCH 93 | Oct 1-Nov 15 |
| Dormancy BBCH 97 | Nov 15-Feb 28 |