Illustration
Blackout Coral Bells
Heuchera 'Blackout'
Also called blackout, heuchera blackout and blackout alumroot
Blackout Coral Bells blooms from June through August.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Blackout Coral Bells
Plant it in part shade. It prefers moderate water. It is hardy in USDA zones 4–9. Expect it to reach about 16 in tall and 16 in wide at maturity, in roughly 2 years (a house reading).
Pets
- Not yet checked for pets.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
No toxicity note is on file for Blackout Coral Bells. That is not a clearance: check its safety for people and pets before planting.
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 Blackout Coral Bells
Plant Blackout Coral Bells 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 9, spring means March to May and fall means August or September. Once settled, it blooms from June to August.
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 Blackout Coral Bells get?
16 intall5 ft 7 inan adult16 inwideSee Blackout Coral Bells 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 Blackout Coral Bells
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Blackout Coral Bells about 16 in apart, center to center, so each plant has room to reach its full width.
Add Blackout Coral Bells 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
Blackout Coral Bells' height, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases, pests and toxicity were checked against 20 published sources on October 10, 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 GardenPlant Finderheight, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases and pests
- Internet Archive (archived page)Mt. Cuba Center, Research Report 2014, Heuchera for the Mid-Atlantic R...height, spread, hardiness zones, sun, water, bloom months and color, soil, diseases and pests
- Plant Addictsthe store this queue came fromheight, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil and pests
- RHSRoyal Horticultural Society (RHS Plants)height, spread, sun, water, bloom months and color, trait tags, soil, diseases and pests
- US plant patent (Google Patents)Google Patents; inventor Diederik A. M. Scheys, the breederheight, spread, hardiness zones, sun, bloom months and color, trait tags, soil, diseases and pests
- Chicago Botanic GardenGlencoe, Illinois; a garden collection entryheight, spread, hardiness zones, sun, water, bloom months and color, trait tags and pests
- Sooner Plant FarmPark Hill, Oklahomaheight, spread, hardiness zones, sun, bloom months and color, trait tags, soil and diseases
- conservationgardenpark.jvwcd.govConservation Garden Park (Jordan Valley Water Conservancy District, Ut...height, spread, hardiness zones, water, bloom months and color, trait tags and pests
- Perennials.com (Heritage Perennials)Valleybrook International Venturesheight, spread, hardiness zones, sun, water, bloom months and color and soil
- pridescorner.comPrides Corner Farms (wholesale grower, Lebanon, Connecticut)height, spread, hardiness zones, sun, water, bloom months and color and pests
- Mt. Cuba CenterTrial Garden (Hockessin, Delaware; Heuchera (Coral Bells) for the Mid-...height, spread, sun, bloom months and color, trait tags and diseases
- Plant Delights NurseryJuniper Level Botanic Garden, North Carolina; an archive pageheight, spread, hardiness zones, sun, bloom months and color and pests
- devilmountainnursery.comDevil Mountain Wholesale Nursery (California)height, spread, hardiness zones, water and bloom months and color
- plants.westonnurseries.comWeston Nurseries (Massachusetts), printing NetPS Plant Finder entry 4790height, spread, hardiness zones, water and bloom months and color
- spl.cde.state.co.usColorado State University, Department of Horticulture and Landscape Ar...height, spread, bloom months and color and diseases
- NC State Extensionthe Heuchera GENUS pagesoil, diseases, pests and toxicity
- spl.cde.state.co.usColorado State University, Department of Horticulture and Landscape Ar...height, spread and bloom months and color
- staudensichtung.deArbeitskreis Staudensichtung (Germany's perennial evaluation working g...height and bloom months and color
- dallasplanttrials.orgDallas Arboretum Trial Gardens (Dallas, Texas; the trial database's en...hardiness zones
- staudensichtung.deArbeitskreis Staudensichtung (Germany's perennial evaluation working g...height
How the checking works, and what each standard covers, is on the verified plants page.
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Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.