Star Magnolia
Magnolia stellata
Magnoliaceae · broadleaf deciduous shrub · introduced
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Magnolia stellata (Magnoliaceae) is a deciduous small tree or large shrub native to Japan. It grows 15 to 20 feet tall and 10 to 15 feet wide, typically branching low to form a rounded, densely twiggy specimen. It is the earliest magnolia to bloom in spring, opening star-shaped white flowers with 12 to 18 strap-shaped tepals on bare branches. The flowers are susceptible to late frost damage.
Star magnolia prefers full sun on well-drained, peaty, organic soil (pH 5.0 to 6.2) with moderate moisture. Drought tolerance is low. Cultivars include 'Royal Star' (larger flowers, slightly later bloom, more frost resistant), 'Waterlily' (pink buds opening white, many tepals), and 'Rosea' (pink-flushed). It blooms on old wood and should be pruned after flowering. Documented problems include bacterial blight, leaf spot, powdery mildew, verticillium wilt, magnolia scale, and yellow poplar weevil. Hardy in Zones 5a to 8b.
Quick Facts
Phenological Calendar
As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. Star Magnolia has passed full bloom (876 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 23, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,593 | Full bloom | — | — |
| Seattle / UW | 1,554 | Full bloom | — | — |
| Kent / Auburn | 1,537 | Full bloom | — | — |
| Olympia / Tumwater | 1,505 | Full bloom | — | — |
| Bellingham / Whatcom | 1,483 | Full bloom | — | — |
| Tacoma / Puyallup | 1,472 | Full bloom | — | — |
| Sequim / Rain Shadow | 1,434 | Full bloom | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| Bloom start BBCH 61 | 628 | Feb 15-Mar 31 |
| ● Full bloom BBCH 65 NOW | 876 | — |
| Bud break BBCH 07 | — | Feb 15-Mar 15 |
| Bloom end / petal fall BBCH 69 | — | Mar 15-Apr 15 |
| Leaf emergence BBCH 11 | — | Mar 15-Apr 15 |
| Fruit/seed development BBCH 71 | — | Mar 15-May 31 |
| Fruit/seed maturity BBCH 85 | — | Jun 1-Aug 31 |
| Leaf drop BBCH 93 | — | Oct 15-Nov 30 |
| Dormancy BBCH 97 | — | Nov 15-Feb 28 |
| Full bloom BBCH 65 | — | — |
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 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.