Illustration
Imperial Blue
Verbena 'Superbena Imperial Blue'
Imperial Blue blooms from May through October.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Imperial Blue
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 9–11. Expect it to reach about 10 in tall and 20 in wide at maturity, in roughly 1 year (not yet checked).
No toxicity note is on file for Imperial Blue. That is not a clearance: check its safety for people and pets before planting.
What this means
Written with AI assistance and not yet checked plant by plant against recorded sources, so treat every fact above as a starting point. Its scientific name was checked against botanical registries, an audit keeps its values consistent with the rest of the library, and a July 2026 review re-read the main facts of every plant then in the library against horticultural authorities without recording a source for each, which is why none of that counts as checked here. The source-by-source check is working through the whole library in the open, and a checked plant says so in this row.
When to plant Imperial Blue
Wait until all danger of frost has passed, then plant out Imperial Blue into warm soil; in most zones that means late spring. Planted then, it flowers from May to October.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 9, the middle of this plant's hardy range, start with zone 9 in February. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Imperial Blue get?
10 intall5 ft 7 inan adult20 inwideSee Imperial 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 Imperial Blue
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Imperial Blue about 20 in apart, center to center, so each plant has room to reach its full width.
Add Imperial Blue to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
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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.