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Delphinium
Delphinium
Delphinium blooms from June through July.
Mature size, 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.
Growing Delphinium
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 3–7. Expect it to reach about 4.6 ft tall and 1.6 ft wide at maturity, in roughly 2 years.
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. For the middle of its hardy zones 3 to 7 range, 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: for the middle of its range, start with zone 5 in April.
Comes in 11 varieties across 4 colors
Same plant, same care - pick the color you are growing.
Good to know about Delphinium
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
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.
Candytuft
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; lower at 10 in, for the front of the border; evergreen, so the bed keeps its shape through winter.
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; evergreen, so the bed keeps its shape through winter.
Goldenrod
Shares full sun and low to moderate water; blooms in late summer as this one finishes; its seed heads stand through winter, for structure and the birds; lower at 3 ft, for the front of the border.
Fountain Grass
Shares full sun and low to moderate water; blooms in late summer as this one finishes; its seed heads stand through winter, for structure and the birds; orange against blue, for contrast.
Glory of the Snow
Shares full sun and moderate water; blooms in early spring, before this one opens; low at 5 in, to carpet the ground beneath; echoes the blue.
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; echoes the blue.
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; purple sits close to blue on the wheel.
Little Bluestem
Shares full sun and low to moderate water; blooms in late summer as this one finishes; its seed heads stand through winter, for structure and the birds; orange against blue, for contrast.
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