Delphinium (Pacific Hybrids)

Tried and Trouble-free Recommended by 4 Professionals
Common Name: larkspur
Type: Herbaceous perennial
Family: Ranunculaceae
Zone: 3 to 7
Height: 4.00 to 6.00 feet
Spread: 2.00 to 3.00 feet
Bloom Time: June to July
Bloom Description: Blue, white, pink, violet
Sun: Full sun
Water: Medium
Maintenance: Medium
Suggested Use: Annual
Flower: Showy, Good Cut
Attracts: Hummingbirds, Butterflies
Tolerate: Deer

Culture

Winter hardy to USDA Zones 3-7 where this delphinium is best grown in fertile, humus rich, medium moisture, well-drained soils in full sun. Performs well in alkaline soils. Prefers climates with cool summer temperatures. Appreciates some part afternoon shade in hot summer climates. Plants often struggle in St. Louis summers, and are generally not recommended for growing in hot and humid summer climates south of USDA Zone 7. Plants require protection from strong winds and rain storms via sheltered growing positions and staking. After bloom, cut back spent flower spikes to the basal foliage to encourage an additional late summer and/or fall bloom.

Pacific Hybrids perennials are short-lived in warm winter/hot summer climates where they are often grown as annuals. If retention of unvaried parent flower color and form is required, purchase new seed as needed or propagate from basal cuttings. Flower color may not come true from seed collected from garden plants. For growth as perennials in cold winter climates, purchase new plants in early spring or plant seed indoors 8-10 weeks prior to last spring frost date. For growth as annuals in warm winter climates, sow seed in pots in mid-summer with transplants set into the ground in October for bloom the following spring.

Noteworthy Characteristics

Delphinium is a genus consisting of over 300 species of annual, biennial and perennial flowering plants. Most delphiniums sold in commerce today are complex hybrids. One such hybrid grouping, commonly known as English hybrid types or Elatum Group (often designated as Delphinium x elatum), features a large number of showy hybrid cultivars which have been introduced into commerce over time in a number of different series or strains which are considered by many gardeners to contain some of the showiest of the delphiniums available in commerce today.

Pacific Hybrids series also known as the Pacific Strain features plants which grow to 4-8’ tall on stems rising from basal clumps of divided palmate green leaves. Flowers bloom in tall slender terminal columnar spikes (spire-like racemes). Each flower spike is densely packed with single to double florets in selected color series including light blue, medium blue, dark blue, white, purple, lavender or pink. Flowers bloom in summer when grown either as perennials or as early spring-planted annuals, but bloom in winter-spring in warm winter climates when planted in summer for growth as annuals. Basal leaves are 5-7 parted and stem leaves are 3 parted.

Genus name comes from the Greek word delphis meaning dolphin in reference to the flower bud shape of some species purportedly resembling a dolphin.

Problems

Delphiniums require considerable maintenance (staking, pruning, deadheading, disease control) in order to perform well in the garden. Delphiniums are generally susceptible to powdery mildew, botrytis blight, leaf spots and crown rot. Plants grown in full sun generally show better resistance to powdery mildew. Water plants at the base to avoid wetting the foliage. Crown rot will inevitably develop if plants are grown in poorly drained soils or planted too deep. Slugs and snails can do significant damage. Watch for aphids, leaf miners, stem borers and mites. Taller plants may need staking and appreciate being sited in locations protected from wind. Plants parts are considered toxic to humans if ingested.

Garden Uses

Superb in cottage gardens. Back of beds and borders. Best in groupings or massed. Plant against a stockade fence for protection from wind. Excellent cut flower. Deer and rabbits usually do not cause problems.