Butterfly weed
Asclepias tuberosa
Apocynaceae · [VERIFY] · native
Last updated
Tuberous-rooted perennial to 1 to 2 feet tall forming bright orange to yellow-orange flower clusters on upright to reclining hairy stems with narrow, lance-shaped leaves. Unlike other milkweeds, lacks milky-sapped stems.
Slow to establish (expect 2 to 3 years to flowering), but worth the wait for drought tolerance and showy blooms; thrives in poor, dry, well-drained soils in full sun. Does not transplant well due to deep taproot; best used in rock gardens, prairies, meadows, or native plant areas.
Quick Facts
Phenological Calendar
As of April 19, 2026, Puget Sound stations range from 1342.9 to 1500.8 GDD₃₂. Butterfly weed typically reaches beginning of flowering at 3405 GDD₃₂, predicted around Jul 3.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 19, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,501 | Pre-season | Beginning of flowering | 1,904 |
| Seattle / UW | 1,465 | Pre-season | Beginning of flowering | 1,940 |
| Kent / Auburn | 1,441 | Pre-season | Beginning of flowering | 1,964 |
| Olympia / Tumwater | 1,415 | Pre-season | Beginning of flowering | 1,990 |
| Bellingham / Whatcom | 1,390 | Pre-season | Beginning of flowering | 2,015 |
| Tacoma / Puyallup | 1,381 | Pre-season | Beginning of flowering | 2,025 |
| Sequim / Rain Shadow | 1,343 | Pre-season | Beginning of flowering | 2,062 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ Beginning of flowering BBCH 61 NEXT | 3405 | — est. Jul 3 (avg) |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Source GDD₅₀ thresholds from Herms 2004 (OSU, Secrest Arboretum, Ohio) and UMD IPMnet (Gill & Klick, mid-Atlantic), converted to GDD₃₂ via Kent bloom-date mapping. Season tracker for Kent / Auburn as of Apr 19, 2026. Predicted dates use 16-day weather forecast through May 5, 2026, then climate normals.