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Delphinium
Delphinium
Delphinium blooms from June through July.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Delphinium
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 3–7. Expect it to reach about 4.5 ft tall and 1.5 ft wide at maturity, in roughly 2 years (not yet checked).
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 Delphinium
Plant Delphinium 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 5, the middle of its hardy zones 3 to 7, spring means April to June and fall means August or September. Once settled, it blooms from June to July.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 5, the middle of this plant's hardy range, start with zone 5 in April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Delphinium get?
4.5 fttall5 ft 7 inan adult1.5 ftwideSee Delphinium 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 Delphinium
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Delphinium about 1.5 ft apart, center to center, so each plant has room to reach its full width.
Add Delphinium 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
Delphinium's height, spread, hardiness zones, sun and trait tags were checked against 11 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.
- Missouri Botanical GardenPlant Finder, Delphinium elatumheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenPacific Hybridsheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionPlant Toolbox, Delphiniumheight, spread, hardiness zones, sun and trait tags
- Walters GardensDelphinium New Zealand 'Stars'height, spread, hardiness zones, sun and trait tags
- Chicago Botanic GardenPlant Finder, Delphinium elatum 'Million Dollar Blue'height, hardiness zones, sun and trait tags
- The Morton ArboretumDelphiniumheight, hardiness zones, sun and trait tags
- Iowa State University Extensionand Outreach, Yard and Garden: Growing Delphiniumsheight, sun and trait tags
- lancaster.unl.eduNebraska Extension in Lancaster County, Delphiniums - A Beautiful Gard...height, sun and trait tags
- University of Illinois ExtensionDelphinium x elatumheight, hardiness zones and sun
- perennialreference.com(Hallson Gardens), Delphiniumsun and trait tags
- RHSRoyal Horticultural Society, Delphiniumsun and trait tags
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 11 varieties across 4 colors
Same genus, similar care - pick the color you are growing.
- Astolat
- Black Knight
- Blue Bird
- Blue Jay
- Blue Mirror
- Galahad
- Guinevere
- King Arthur
- Magic Fountains Cherry Blossom
- Magic Fountains Dark Blue
- Summer Skies
Compare every variety in the Delphinium group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Astolat | Pink | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Black Knight | Purple | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Blue Bird | Blue | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Blue Jay | Blue | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Blue Mirror | Blue | Jun–Aug | Zones 3–7 | Full sun | 16 in × 12 in |
| Delphiniumthis page | Blue | Jun–Jul | Zones 3–7 | Full sun | 4.5 ft × 1.5 ft |
| Galahad | White | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Guinevere | Pink | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| King Arthur | Purple | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
| Magic Fountains Cherry Blossom | Pink | Jun–Jul | Zones 3–7 | Full sun | 2.5 ft × 1.5 ft |
| Magic Fountains Dark Blue | Blue | Jun–Jul | Zones 3–7 | Full sun | 2.5 ft × 1.5 ft |
| Summer Skies | Blue | Jun–Jul | Zones 3–7 | Full sun | 5 ft × 1.5 ft |
Good to know about Delphinium
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Safety
All parts are poisonous to people and pets; the diterpenoid alkaloids are most concentrated in young growth and seeds. NC State rates the poison severity High. per ASPCA and NC State
Worth knowing
The same toxins that make delphinium dangerous to eat make it deer- and rabbit-proof: Clemson lists it among plants deer avoid precisely because of those toxic compounds. per Clemson and NC State
Height varies by type
Listed heights vary widely by type. Dwarf native larkspurs reach only 0.3 to 0.9 m; the tall garden hybrids most gardeners plant reach 0.9 to 1.5 m, sometimes taller. per NC State and Illinois
Needs cool summers
Fundamentally a cool-summer plant. It struggles south of zone 7, where heat and humidity shorten its life; in warm regions the heat-tolerant belladonna type is the better choice. per NC State and Iowa State
Short-lived perennial
Plan for a short life: most plants last only 2 to 3 years (NC State's elatum page says 3 to 5), shorter in heavy soil or heat. per NC State and Iowa State
Staking is essential
The tall spikes ride on hollow stems that snap in wind and rain. Stake early, by mid-spring or when plants reach about 30 cm, before the buds open. per NC State and Iowa State
Common diseases to watch
Powdery mildew is common on the leaves. The real killers are wet-soil crown and root rots. Full sun, airflow, and sharp drainage are the best defenses. per NC State and UC IPM
What pairs well with Delphinium
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Goldenrod
Shares full sun and low to moderate water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Rock Cress
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; low at 4 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Perennial Sunflower
Shares full sun and moderate water; blooms in late summer as this one finishes; both are strong pollinator plants, and they feed in different months; its seed heads stand through winter, for structure and the birds.
Wisteria
Shares full sun and moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; climbs to 26 ft behind it, height without the footprint.
Autumn Crocus
Shares full sun and moderate water; blooms in early fall, extending the bed's season; low at 6 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Hyacinth
Shares full sun and moderate water; blooms in early spring, before this one opens; lower at 10 in, for the front of the border; both offer pollinator forage, in different months.
Sweet Alyssum
Shares full sun and moderate water; overlaps, then carries the display into mid fall; low at 5 in, to carpet the ground beneath; both are strong pollinator plants.
Windflower
Takes full sun to part sun and moderate water; blooms in early spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
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