Illustration
Crimson Comet Buttonbush
Cephalanthus occidentalis 'Smcbm'
Also called red moon rising and crimson comets buttonbush
Crimson Comet Buttonbush blooms from June through August.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Crimson Comet Buttonbush
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 5–9. Expect it to reach about 8 ft tall and 7.5 ft wide at maturity, in roughly 4 years (a house reading).
Pets
- Not yet checked for pets.
- Listed as poisonous to people by 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
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. 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 Crimson Comet Buttonbush
Plant Crimson Comet Buttonbush 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 7, the middle of its hardy zones 5 to 9, spring means March to May and fall means September or October. 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 7, the middle of this plant's hardy range, start with zone 7 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Crimson Comet Buttonbush get?
8 fttall5 ft 7 inan adult7.5 ftwideSee Crimson Comet Buttonbush 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 Crimson Comet Buttonbush
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Crimson Comet Buttonbush about 7.5 ft apart, center to center, so each plant has room to reach its full width.
Add Crimson Comet Buttonbush 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
Crimson Comet Buttonbush's height, spread, hardiness zones, sun, water, bloom color and trait tags were checked against 9 published sources on October 19, 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.
- abnativeplants.comAmerican Beauties Native Plants, brandheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- covingtonnursery.comCovington's Nursery & Landscapeheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- Plant Addictsheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- archive.midwestgroundcovers.comMidwest Groundcovers, publisher-maintained former websiteheight, spread, hardiness zones, sun, water and bloom months and color
- onlinetrees.comOnline Treesheight, spread, hardiness zones, sun, water and bloom months and color
- NC State ExtensionGardener Plant Toolbox, species pagesun, water and trait tags
- pridescorner.comPrides Corner Farms, American Beauties growerheight, spread and hardiness zones
- Missouri Botanical GardenPlant Finder, species pagewater and trait tags
- US plant patent (Google Patents)US Plant Patent PP33,564, Timothy D. Wood / Spring Meadow Nursery, via...bloom months and color
How the checking works, and what each standard covers, is on the verified plants page.
Where it grows wild
A garden form of Buttonbush (Cephalanthus occidentalis)
Its wild parent is native to 34 states and 4 provinces.
Its parent's own page: Buttonbush.
United States: Alabama, Arizona, Arkansas, California, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin and 22 more
Canada: New Brunswick, Nova Scotia, Ontario, Quebec
Range data from the World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 4.0, adapted) and USDA PLANTS. How the native range is credited.
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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.