Gibraltar Azalea
Rhododendron 'Gibraltar'
Ericaceae · broadleaf deciduous shrub · introduced
Last updated
An upright deciduous azalea reaching 6 to 8 feet tall and 5 to 7 feet wide. Large funnel-shaped flowers with frilled edges in vivid flame-orange, carried in dome-shaped trusses. Deciduous azalea bloom on old wood; flowers appear before or with emerging leaves. A Knap Hill-Exbury hybrid attributed to Anthony Waterer (1947) or Edmund de Rothschild, holding an RHS Award of Garden Merit.
Among the most vivid orange-flowered deciduous azaleas in commerce. Hardy to approximately -20°F (Zone 5a-8a). Full sun to part shade on acidic, well-drained soil (pH 4.5-6.0). Knap Hill-Exbury hybrids generally tolerate full sun well. Substantial mature size (8 to 10 feet) requires generous spacing. Good fall foliage color. 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 8 |
| Full bloom BBCH 65 | May 1-May 18 |
| Bloom end BBCH 69 | May 12-May 28 |
| Bud set BBCH 55-59 | Jul 15-Sep 15 |