Alder Buckthorn

Rhamnus alnifolia

Rhamnaceae · broadleaf deciduous shrub · introduced

Last updated March 8, 2026

Data Coverage 3 of 6 dimensions

Site Data

Threats

Cultivars

Phenology

GDD Thresholds

Puget Sound

Quick Facts

Height

3 ft

Growth Rate

Moderate

Light

Part Shade

Soil

Wet Tolerant

Water

High

Hardiness

Zone Zones 4a–9b

Bloom Time

May 1-May 31

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 31	First open flowers visible; flowers green
Bloom end / petal fall BBCH 69	May 15-Jun 15	Last petals falling; flower structures fading
Fruit/seed development BBCH 71	Jun 1-Aug 31	Fruit or seed structures forming
Leaf drop BBCH 93	Oct 15-Nov 30	Leaves yellowing and dropping; no significant fall color display
Dormancy BBCH 97	Nov 15-Feb 28	Leafless; no active growth; dormant buds set