Trailing Blackberry Western Blackberry California Blackberry Dewberry
Rubus ursinus
Rosaceae · vine groundcover · native
Last updated
Trailing blackberry (Rubus ursinus), also called western blackberry, California blackberry, or dewberry, is a broadleaf shrub in the Rosaceae family native to western North America from British Columbia to California, east to Idaho, south to Mexico. It reaches 10-20 ft in length with a trailing habit, forming sprawling thickets in waste places, fields, and canyons below 1,000 meters.
Trailing blackberry is hardy in zones 3a-8b and tolerates full sun to shade with moist soil (pH 4.5-8.5) and moderate water. Thirty-two diseases and 4 pests are documented. The fruit has a moderate edibility rating (3/5). This is the parent species of the cultivated marionberry and other trailing blackberry cultivars.
Quick Facts
Phenological Calendar
As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Trailing Blackberry Western Blackberry California Blackberry Dewberry has reached 'leaf emergence' (953 GDD₃₂) and is approaching 'fall color / leaf senescence', predicted around Apr 6.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | 'Fall color / leaf senescence' | 'Flower buds visible' | 224 |
| Seattle / UW | 1,171 | 'Leaf emergence' | 'Fall color / leaf senescence' | 2 |
| Kent / Auburn | 1,111 | 'Leaf emergence' | 'Fall color / leaf senescence' | 62 |
| Olympia / Tumwater | 1,106 | 'Leaf emergence' | 'Fall color / leaf senescence' | 67 |
| Bellingham / Whatcom | 1,101 | 'Leaf emergence' | 'Fall color / leaf senescence' | 72 |
| Tacoma / Puyallup | 1,075 | 'Leaf emergence' | 'Fall color / leaf senescence' | 98 |
| Sequim / Rain Shadow | 1,070 | 'Leaf emergence' | 'Fall color / leaf senescence' | 103 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Bud break' BBCH '07' | 842 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 953 | '' |
| ○ 'Fall color / leaf senescence' BBCH '93' NEXT | 1173 | '' est. Apr 6 (forecast) |
| 'Flower buds visible' BBCH '51' | 1405 | '' est. Apr 18 (forecast) |
| 'First bloom' BBCH '61' | 1612 | '' est. Apr 29 (avg) |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? GDD₃₂ thresholds from USA National Phenology Network citizen science observations (WA+OR). Season tracker for Kent / Auburn as of Apr 3, 2026. Predicted dates use 16-day weather forecast through Apr 19, 2026, then climate normals.