Illustration
Black Knight
Buddleia davidii 'Black Knight'
Black Knight blooms from June through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Black Knight
Plant it in full sun. It prefers low water. It is hardy in USDA zones 5–9. Expect it to reach about 6.5 ft tall and 6 ft wide at maturity, in roughly 3 years (not yet checked).
No toxicity note is on file for Black Knight. 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 Knight
Plant Black Knight 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 September.
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 Black Knight get?
6.5 fttall5 ft 7 inan adult6 ftwideSee Black Knight 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 Knight
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Black Knight about 6 ft apart, center to center, so each plant has room to reach its full width.
Add Black Knight 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 Knight's height, spread, hardiness zones, sun and trait tags were checked against 8 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.
- boethingtreeland.comBoething Treeland Farmsheight, spread, hardiness zones, sun and trait tags
- buddlejacollection.comNational Plant Collection of Buddleja, Longstock Park (Buddleja Collec...height, spread, hardiness zones, sun and trait tags
- Missouri Botanical Gardenheight, spread, hardiness zones, sun and trait tags
- RHSheight, spread, sun and trait tags
- Sooner Plant Farmheight, spread, hardiness zones and sun
- Plant Delights Nurseryheight, hardiness zones and sun
- navigate.botanicgardens.orgDenver Botanic Gardens Gardens Navigatorhardiness zones and sun
- NC State Extensionspecies page, zones and sun onlyhardiness zones and sun
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.