Trailing Blackberry Western Blackberry California Blackberry Dewberry
'First bloom'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
Primary Spore Release
Spring New Growth - Early Infection Window
Root Colonization Period
Active Below-ground Growth
+ 2 more — see full disease and pest lists below
Phenological Calendar
As of May 14, 2026, Puget Sound stations range from 1926.1 to 2121.1 GDD₃₂. Trailing Blackberry Western Blackberry California Blackberry Dewberry has passed 'first bloom' (1612 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' | 842 | '' |
| 'Leaf emergence' BBCH '11' | 953 | '' |
| 'Fall color / leaf senescence' BBCH '93' | 1173 | '' |
| 'Flower buds visible' BBCH '51' | 1405 | '' |
| ● 'First bloom' BBCH '61' NOW | 1612 | '' |
Source: 'NPN citizen science observations (WA+OR), n=55, 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.