Illustration
Black Hat Rhododendron
Rhododendron 'NCRX2'
Black Hat Rhododendron blooms from April through April.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Black Hat Rhododendron
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 4–8. Expect it to reach about 3 ft tall and 3 ft wide at maturity, in roughly 4 years (checked).
Is Black Hat Rhododendron toxic to dogs or cats?
- Listed as toxic to dogs and cats by NC State Extension, Pet Poison Helpline and Royal Horticultural Society.
- Listed as poisonous to people by NC State Extension and Royal Horticultural Society.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
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 Black Hat Rhododendron
Plant Black Hat 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 in April.
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 Black Hat Rhododendron get?
3 fttall5 ft 7 inan adult3 ftwideSee Black Hat 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 Black Hat Rhododendron
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Black Hat Rhododendron about 3 ft apart, center to center, so each plant has room to reach its full width.
Add Black Hat 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
Black Hat Rhododendron's height, spread, hardiness zones, sun, water, bloom months and color, years to mature size, trait tags, soil, diseases, pests and toxicity were checked against 8 published sources on October 5, 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.
- NC State Extensioncultivar pageheight, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases and pests
- Nature Hills Nurseryheight, spread, hardiness zones, sun, water, bloom months and color, soil, pests and toxicity
- Plant Addictsthe storeheight, spread, hardiness zones, sun, water, bloom months and color, trait tags and soil
- Proven Winnersthe brandheight, spread, hardiness zones, sun, water, bloom months and color, trait tags and soil
- US plant patent (Google Patents)the breeder's patentheight, spread, hardiness zones, bloom months and color, years to mature size, trait tags and diseases
- NC State ExtensionRhododendron genus pagesun, trait tags, soil, diseases, pests and toxicity
- rhododendron.orgAmerican Rhododendron Society plant descriptionheight, hardiness zones, bloom months and color and years to mature size
- pridescorner.comPrides Corner Farms (grower)height, spread and hardiness zones
How the checking works, and what each standard covers, is on the verified plants page.
Good to know about Black Hat Rhododendron
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
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
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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.