Glacier Azalea
Rhododendron 'Glacier'
Ericaceae · broadleaf evergreen shrub · introduced
Last updated
A dense, upright evergreen azalea reaching 4 to 5 feet in 10 years and 5 to 7 feet at maturity. Funnel-shaped pure white flowers with subtle dorsal spotting, 2 to 2½ inches wide, in clusters of 2 to 3 blooms. Midseason flowering. A Glenn Dale hybrid bred by Benjamin Morrison at the USDA Plant Introduction Station, drawn from R. kaempferi, R. mucronatum, and related species.
Hardy to approximately -10°F (Zone 6a-9a). Part shade to full sun on acidic, well-drained soil (pH 4.5-6.0). Glenn Dale hybrids generally tolerate higher light than Kurume types. The clean white flowers and all-green foliage (no winter bronzing) give it a quieter landscape presence than the more commonly planted colored azaleas. Twenty-one diseases and 15 pests documented at the genus level. All parts contain grayanotoxins and are toxic if ingested.
Quick Facts
Root Colonization (Spring–Fall)
Infection at Bud Break
Apothecia Formation & Spore Release
Aecial Stage (Alternate Host)
+ 13 more — see full disease and pest lists below
Phenological Calendar
| Stage | Typical Window |
|---|---|
| Bud swell BBCH 01-03 | Mar 15-Apr 15 |
| Bloom start BBCH 61 | Apr 22-May 5 |
| Full bloom BBCH 65 | Apr 28-May 12 |
| Bloom end BBCH 69 | May 8-May 22 |
| Bud set BBCH 55-59 | Jul 15-Sep 15 |