Creeping St. John's Wort Aaron's Beard
Leaf emergenceHypericum calycinum
Hypericaceae · vine groundcover · introduced
Last updated
Creeping St. John's wort (Hypericum calycinum, Hypericaceae) is a semi-evergreen, stoloniferous subshrub from southeastern Europe and Asia Minor, reaching 12 to 18 inches tall (occasionally 3 feet) with a spread of 24 inches or more. Large yellow, five-petaled, rose-like flowers (5 to 8 centimeters) with bushy reddish-anthered stamens bloom in early summer and sometimes through the season.
Creeping St. John's wort grows in sun to shade on adaptable, well-drained soils, hardy in Zones 6a to 8b. It tolerates drought, erosion, and dry soil. Documented diseases include root rot and rust. The species can be invasive in some regions via creeping rhizomes, above-ground stems, and seed dispersal. No cultivars are documented.
Plant Profile
Size & Form
Site Requirements
Ornamental Interest
Field Observations
Uredinial Stage (Summer)
Diseases: Regionally Documented (1)
Phenological Calendar
As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Creeping St. John's Wort Aaron's Beard has passed leaf emergence (1624 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,673 | Leaf emergence | — | — |
| Kent / Auburn | 2,665 | Leaf emergence | — | — |
| Seattle / UW | 2,610 | Leaf emergence | — | — |
| Olympia / Tumwater | 2,570 | Leaf emergence | — | — |
| Tacoma / Puyallup | 2,535 | Leaf emergence | — | — |
| Bellingham / Whatcom | 2,533 | Leaf emergence | — | — |
| Sequim / Rain Shadow | 2,436 | Leaf emergence | — | — |
View full calendar (6 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| Bud break BBCH 07 | — | Feb 15-Mar 15 |
| ● Leaf emergence BBCH 11 NOW | 1624 Observed | Late April |
| Bloom start BBCH 61 | — | Jun 1-Jun 30 |
| Bloom end / petal fall BBCH 69 | — | Jun 15-Jul 15 |
| Leaf drop BBCH 93 | — | Oct 15-Nov 30 |
| Dormancy BBCH 97 | — | Nov 15-Feb 28 |
Source: 'Field observation, Kent, WA, 2026-04-27' About GDD₃₂ →
Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.