Illustration
Empire Blue
Buddleia davidii 'Empire Blue'
Empire Blue blooms from June through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Empire Blue
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 (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 Empire Blue. That is not a clearance: check its safety for people and pets before planting.
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 Empire Blue
Plant Empire Blue 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 Empire Blue get?
6.5 fttall5 ft 7 inan adult6 ftwideSee Empire Blue 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 Empire Blue
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Empire Blue about 6 ft apart, center to center, so each plant has room to reach its full width.
Add Empire Blue 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
Empire Blue's height, spread, hardiness zones, sun, water, bloom color and trait tags were checked against 8 published sources on October 20, 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.
- siteone.comSiteOne Landscape Supplyheight, spread, hardiness zones, sun, bloom months and color and trait tags
- buddlejacollection.comBuddleja Collectionheight, spread, hardiness zones, sun and trait tags
- phelangardens.comPhelan Gardensheight, spread, bloom months and color and trait tags
- jcra.ncsu.eduJC Raulston Arboretum, NC State Universitysun, bloom months and color and trait tags
- Iowa State University Extensionbloom months and color and trait tags
- NC State Extensionsun, water and trait tags
- RHSRoyal Horticultural Societywater and bloom months and color
- Chicago Botanic Gardenheight and spread
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.