Illustration
Black Ball
Centaurea cyanus 'Black Ball'
Black Ball blooms from May through July.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Black Ball
Plant it in full sun. It prefers low water. It is hardy in USDA zones 2–11. Expect it to reach about 2.5 ft tall and 1 ft wide at maturity, in roughly 1 year (not yet checked).
No toxicity note is on file for Black Ball. That is not a clearance: check its safety for people and pets before planting.
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 Black Ball
Wait until all danger of frost has passed, then plant out Black Ball into warm soil; in most zones that means late spring. Planted then, it flowers from May to July.
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 April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Black Ball get?
2.5 fttall5 ft 7 inan adult1 ftwideSee Black Ball 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 Ball
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Black Ball about 1 ft apart, center to center, so each plant has room to reach its full width.
Add Black Ball 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 Ball's height, spread, hardiness zones, sun and trait tags were checked against 13 published sources on July 29, 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.
- tomorrowseeds.comTomorrowSeedsheight, spread, hardiness zones, sun and trait tags
- Outsideprideheight, hardiness zones, sun and trait tags
- vermontwildflowerfarm.comVermont Wildflower Farmheight, hardiness zones, sun and trait tags
- applewoodseed.comApplewood Seed Companyheight, sun and trait tags
- BBC Gardeners' WorldMagazineheight, spread and sun
- Missouri Botanical Gardenhardiness zones, sun and trait tags
- NC State ExtensionPlant Toolboxhardiness zones, sun and trait tags
- plant-world-seeds.comPlant World Seedsheight, sun and trait tags
- RHSRoyal Horticultural Societyheight, spread and sun
- Swallowtail Garden Seedsheight, sun and trait tags
- adaptiveseeds.comAdaptive Seedsheight and sun
- victoryseeds.comVictory Seed Companyheight and trait tags
- higgledygarden.comHiggledy Gardenheight
How the checking works, and what each standard covers, is on the verified plants page.
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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.