Ash

Sorbaria sorbifolia

Rosaceae · broadleaf deciduous shrub · introduced

Last updated

Quick Facts

Height
6 ft
Spread
9 ft
Growth Rate
Fast
Light
Sun to Part Shade
Soil
Moist
Water
Moderate
Hardiness
Zone Zones 2a–7b
Bloom Time
June to July
Origin
Northern Asia (Siberia, China, Korea, Japan)
Watch for this season

Spring Emergence / Primary Infection

Field Observations

Sorbaria sorbifolia 'Sem' - new leaves
Field Observation
Sorbaria sorbifolia 'Sem' · False Spiraea
new leaves
April 20, 2026 · Lake Wilderness Arboretum · 1,509 GDD₃₂ · BBCH 11

Phenological Calendar

As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Ash typically reaches 'first bloom' at 3276 GDD₃₂, predicted around Jun 26.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of May 13, 2026
Station GDD₃₂ Current Stage Next To Go
Issaquah / East King 2,098 Pre-season 'First bloom' 1,178
Kent / Auburn 2,089 Pre-season 'First bloom' 1,187
Seattle / UW 2,063 Pre-season 'First bloom' 1,213
Olympia / Tumwater 2,025 Pre-season 'First bloom' 1,251
Tacoma / Puyallup 1,993 Pre-season 'First bloom' 1,283
Bellingham / Whatcom 1,972 Pre-season 'First bloom' 1,304
Sequim / Rain Shadow 1,906 Pre-season 'First bloom' 1,370
Stage GDD32 Typical Window
'First bloom' BBCH '61' NEXT 3276 '' est. Jun 26 (avg)
Leaf emergence BBCH 11
Range: 2515–2896 GDD₃₂ (6yr)

Source: 'Master catalog (OSU), GDD50 base' About GDD₃₂ →

Season tracker for Kent / Auburn as of May 13, 2026. Predicted dates use 16-day weather forecast through May 29, 2026, then climate normals.

Diseases: Other Associations (1)

Pests: Other Associations (1)

Cultivars (2)

'Bococot' Cherry On Top™
Cherry On Top™ Sorbaria, Cherry On Top™ Ash Leaf Spiraea
Sorbaria sorbifolia 'Sem' – new leaves
'Sem'
Sem Ash Leaf Spiraea

Suitable for zones 2-7b; at the warm edge of its range in Zone 8b. The heavy clay soils of the Kent valley may naturally suppress aggressive suckering. NC State and MBG report no serious insect or disease problems. 'Sem' cultivar preferred for managed landscapes due to reduced suckering. Useful for erosion control on slopes.

Data Maturity
Baseline Extension data. Expert review underway.