Cascara
Frangula purshiana
Rhamnaceae · broadleaf deciduous tree · native
Last updated
Cascara (Frangula purshiana, Rhamnaceae; synonym Rhamnus purshiana) is a native deciduous tree or shrub found from British Columbia south to California and east to western Montana, reaching up to 50 feet as a tree or about 15 feet as a shrub. Alternate, elliptic to oblong leaves (5 to 15 centimeters) have 10 to 15 conspicuous parallel veins. Fall color is pure yellow in shade, mixed with orange, red, and purple in sun. Small green-white flowers yield purplish-black drupes (8 millimeters) with a sickly sweet taste.
Cascara grows in full sun to shade on moist soils (pH 4.5 to 8.5), hardy in Zones 3b to 8b. It is found in rich bottomlands and canyon sides. The cured bark was the principal over-the-counter laxative ingredient in North America until 2002; fresh bark causes severe gastrointestinal distress. Fruit is eaten and dispersed by birds, bears, and raccoons. Documented diseases include leaf spot. No cultivars are in the trade.
Quick Facts
Phenological Calendar
As of May 14, 2026, Puget Sound stations range from 1926.1 to 2121.1 GDD₃₂. Cascara has passed 'first bloom' (1613 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 14, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,121 | 'First bloom' | — | — |
| Kent / Auburn | 2,113 | 'First bloom' | — | — |
| Seattle / UW | 2,085 | 'First bloom' | — | — |
| Olympia / Tumwater | 2,047 | 'First bloom' | — | — |
| Tacoma / Puyallup | 2,016 | 'First bloom' | — | — |
| Bellingham / Whatcom | 1,994 | 'First bloom' | — | — |
| Sequim / Rain Shadow | 1,926 | 'First bloom' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Bud break' BBCH '07' | 856 | '' |
| 'Leaf emergence' BBCH '11' | 981 | '' |
| ● 'First bloom' BBCH '61' NOW | 1613 | '' |
| 'Fruit ripe' BBCH '85' | — | 'August-September' |
| 'Leaf senescence' BBCH '93' | — | 'October-November' |
Source: 'NPN citizen science observations (WA+OR), n=38, median. services.usanpn.org' About GDD₃₂ →
Season tracker for Kent / Auburn as of May 14, 2026. Predicted dates use 16-day weather forecast through May 30, 2026, then climate normals.