Illustration
Photo credits and licenses
Real photographs from naturalists and photographers worldwide, each used under its own license. Credit: Photo by Tatyana Petrenko / iNaturalist (CC BY). How photos are sourced →
Rhododendron
Rhododendron
Rhododendron blooms from May through June.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Rhododendron
Plant it in part shade. It prefers moderate water. It is hardy in USDA zones 4–8. Expect it to reach about 6 ft tall and 6 ft wide at maturity, in roughly 5 years (not yet checked).
What was checked
Mature height and spread, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not, and each fact above says which. 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 Rhododendron
Plant Rhododendron 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 4 to 8, spring means March to May and fall means August or September. Once settled, it blooms from May to June.
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 Rhododendron get?
6 fttall5 ft 7 inan adult6 ftwideSee Rhododendron 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 Rhododendron
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Rhododendron about 6 ft apart, center to center, so each plant has room to reach its full width.
Add Rhododendron 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
Rhododendron's height, spread, hardiness zones, sun and trait tags were checked against 8 published sources on July 30, 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 GardenRhododendron catawbienseheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenRhododendron arborescensheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionRhododendron, the genus entryheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionRhododendron catawbienseheight, spread, hardiness zones, sun and trait tags
- The Morton ArboretumRhododendron P.J.M., a hybrid cultivarheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenRhododendron maximumheight, spread, hardiness zones and sun
- Clemson Home and Garden Information Centerthe genusheight, spread and sun
- The Morton ArboretumCatawba rhododendron, Rhododendron catawbienseheight, hardiness zones and sun
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 14 varieties across 6 colors
Same genus, similar care - pick the color you are growing.
- Aglo
- Album
- Anah Kruschke
- Blue Peter
- Boule de Neige
- Capistrano
- Cunningham's White
- English Roseum
- Nova Zembla
- PJM
- Purple Splendor
- Roseum Elegans
- Scintillation
- Yaku Princess
Compare every variety in the Rhododendrons group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Aglo | Pink | May | Zones 4–8 | Part shade | 3 ft × 3 ft |
| Album | White | May | Zones 4–8 | Part shade | 6 ft × 6 ft |
| Anah Kruschke | Purple | May–Jun | Zones 5–9 | Part shade | 6 ft × 5 ft |
| Blue Peter | Blue | May–Jun | Zones 5–8 | Part shade | 5 ft × 5 ft |
| Boule de Neige | White | May–Jun | Zones 4–8 | Part shade | 4 ft × 5 ft |
| Capistrano | Yellow | May–Jun | Zones 5–8 | Part shade | 4 ft × 6 ft |
| Cunningham's White | White | May–Jun | Zones 4–8 | Part shade | 5 ft × 5 ft |
| English Roseum | Pink | May–Jun | Zones 4–8 | Part shade | 6 ft × 6 ft |
| Nova Zembla | Red | May–Jun | Zones 5–8 | Part shade | 6 ft × 6 ft |
| PJM | Pink | Apr–May | Zones 4–8 | Part shade | 4 ft × 4 ft |
| Purple Splendor | Purple | May–Jun | Zones 5–8 | Part shade | 5 ft × 5 ft |
| Rhododendronthis page | Purple | May–Jun | Zones 4–8 | Part shade | 6 ft × 6 ft |
| Roseum Elegans | Pink | May–Jun | Zones 4–8 | Part shade | 6 ft × 6 ft |
| Scintillation | Pink | May–Jun | Zones 5–8 | Part shade | 5 ft × 5 ft |
| Yaku Princess | Pink | May–Jun | Zones 5–8 | Part shade | 3.5 ft × 4 ft |
Good to know about Rhododendron
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Safety
Toxic to dogs, cats, and horses: all parts and the nectar hold grayanotoxins. Even a few leaves can cause vomiting, weakness, and dangerous heart effects. per ASPCA
Worth knowing
Drainage decides everything. The same soggy, poorly drained soil the shallow roots cannot handle is what lets root rot, the top killer, take hold. Plant high, never wet. per Clemson and University of Maryland
Diagnose dieback before treating
Branch dieback has more than one cause: a wet-weather Phytophthora blight (UConn) or a canker fungus on stressed plants (Clemson). Diagnose which before you spray. per UConn and Clemson
Prune right after flowering
It blooms on old wood and sets next year's buds in summer, so prune and deadhead right after the flowers fade. A later cut costs next spring's show. per Clemson and UGA
Lace bug worse in sun
The main pest, lace bug, stipples the leaves pale gray and is far worse on hot, sunny, dry sites. Dappled shade with afternoon relief keeps it in check. per Clemson and UC IPM
Needs acid soil
Grows only in strongly acid soil, roughly pH 4.5 to 5.5. Too high and iron locks up, so new leaves yellow between green veins. Test before amending. per University of Maryland and Clemson
Nectar makes 'mad honey'
Bees that work rhododendron flowers can make grayanotoxin-laced 'mad honey', which has sickened people. The nectar carries the same toxin as the leaves. per PubMed Central and NC State
What pairs well with Rhododendron
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Windflower
Takes part sun to part shade and moderate water; blooms in early spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
Wishbone Flower
Shares part shade and moderate water; overlaps, then carries the display into early fall; low at 10 in, to carpet the ground beneath; both are strong pollinator plants.
Eastern Redbud
Takes part sun to part shade and moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 23 ft, for the layer behind it.
Primrose
Shares part shade and moderate water; opens in early spring and overlaps into this one's season; low at 8 in, to carpet the ground beneath; both offer pollinator forage.
Lobelia
Takes part sun to part shade and moderate water; low at 8 in, to carpet the ground beneath; overlaps, then carries the display into early fall; both are strong pollinator plants.
Flowering Dogwood
Shares part shade and moderate water; opens in mid spring and overlaps into this one's season; both are strong pollinator plants; taller at 23 ft, for the layer behind it.
Turtlehead
Takes part sun to part shade and moderate to high water; blooms in late summer, extending the bed's season; both are strong pollinator plants, and they feed in different months; lower at 3 ft, for the front of the border.
Serviceberry
Takes part sun to part shade and moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 20 ft, for the layer behind it.
Explore similar plants
You might also like
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.