Field Horsetail
Equisetum arvense
Equisetaceae · fern ally · native
Last updated
Data Maturity Baseline
This profile contains verified botanical data. Regional field notes and expert review are in progress.
Field Observations
Field Observation
Equisetum arvense · Field Horsetail
new growth
Quick Facts
Height
1-2 ft (vegetative shoots)
Spread
indefinite (rhizomatous)
Growth Rate
Fast
Light
Full Sun to Partial Shade
Soil
Moist To Wet; Tolerates Poor Drainage
Water
Moderate to high
Hardiness
Zone Zones 2–11
Origin
Pacific Northwest native
Phenological Calendar
As of April 28, 2026, Puget Sound stations range from 1536.6 to 1694.7 GDD₃₂. Field Horsetail has passed new growth (1580 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 28, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,695 | new growth | — | — |
| Seattle / UW | 1,654 | new growth | — | — |
| Kent / Auburn | 1,644 | new growth | — | — |
| Olympia / Tumwater | 1,603 | new growth | — | — |
| Bellingham / Whatcom | 1,591 | new growth | — | — |
| Tacoma / Puyallup | 1,572 | Pre-season | new growth | 8 |
| Sequim / Rain Shadow | 1,537 | Pre-season | new growth | 43 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ● new growth BBCH 11 NOW | 1580 | April-May |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Hover over GDD values for source details. Season tracker for Kent / Auburn as of Apr 28, 2026. Predicted dates use 16-day weather forecast through May 14, 2026, then climate normals.