Illustration
Gibraltar
Rhododendron 'Gibraltar'
Also called exbury azaleas
Gibraltar blooms from April through May.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Gibraltar
Plant it in part shade. It prefers moderate water. It is hardy in USDA zones 5–8. Expect it to reach about 5 ft tall and 4 ft wide at maturity, in roughly 4 years (a house reading).
What was checked
Mature height and spread, hardiness zones, sun, water, bloom months and color and the trait tags were checked against named botanical sources for this plant, with what the sources could not settle written down; years to mature size rests on a recorded house rule where no publisher states one, and is marked so; its common name and alternate names have not been checked yet. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Gibraltar
Plant Gibraltar in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 6, the middle of its hardy zones 5 to 8, spring means March to May and fall means August or September. Once settled, it blooms from April to May.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Gibraltar get?
5 fttall5 ft 7 inan adult4 ftwideSee Gibraltar in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Gibraltar
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Gibraltar about 4 ft apart, center to center, so each plant has room to reach its full width.
Add Gibraltar to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Gibraltar's height, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases, pests and toxicity were checked against 11 published sources on August 24, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical Gardenheight, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases and pests
- RHSRoyal Horticultural Societyheight, spread, sun, water, bloom months and color, soil, diseases, pests and toxicity
- NC State ExtensionRhododendron hybrids: Exbury, Ghent, Knaphill Azaleashardiness zones, sun, bloom months and color, soil, diseases, pests and toxicity
- Pleasant Run Nurseryheight, spread, hardiness zones, sun, bloom months and color and trait tags
- University of Georgia ExtensionB670, Selecting and Growing Azaleaswater, bloom months and color, trait tags, soil, diseases and pests
- fieldstonegardens.comFieldstone Gardensheight, spread, hardiness zones, sun and trait tags
- scholar.lib.vt.eduJournal American Rhododendron Society v60n1, Rhododendron of the Year...height, hardiness zones and diseases
- ASPCAAnimal Poison Control, Toxic and Non-Toxic Plant List for Catstoxicity
- ASPCAAnimal Poison Control, Toxic and Non-Toxic Plant List for Dogstoxicity
- ASPCAAnimal Poison Control, Toxic and Non-Toxic Plant List for Horsestoxicity
- shop.glendoick.comGlendoick Garden Centre (specialist rhododendron nursery, Scotland)height
How the checking works, and what each standard covers, is on the verified plants page.
Good to know about Gibraltar
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Safety
All parts contain grayanotoxins. Toxic to dogs, cats and horses: vomiting, diarrhea, weakness, and in serious cases cardiac failure. Pets and livestock are poisoned more readily than people. per ASPCA
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.