Elegant, beautiful, blue & Fussy
Common Name: delphinium, perennial larskspur
Botanical Name: Delphinium
Form: upright, narrow, columnar
Family: Ranunculaceae (buttercup family)
Species: 300 species
Plant Type: herbaceous deciduous perennial
Mature Size: depends on type, generally 5 to 6ft tall and 2ft wide
Origin: Northern hemisphere, mountain regions of Africa
Hardiness Zone: 3 to 8
Foliage: 3 to 7 deeply pointed lobes per leaf palmately arranged, toothed margins, green leaves cluster at the bottom of the plant
Flowers: Borne on erect stems from 10 cm (3.9”) to meters (6’.62”) depending on species, raceme inflorescences (flower clusters), five sepals form a tube with a nectar rich spur at its base. Four small true petals lie inside the flower (referred to as a ‘bee’), which may or may not be the same colour of the sepals. Flowers are usually deep blue, but there’s also pink, red, yellow or white species, hybrids and varieties. Blossoms June, July and August.
Fruit: silique pod with many small black seeds
Stems: non woody, tall, herbaceous and will bend with the weight of the flowers
Exposure: full sun for 6 to 8 hours, shelter from wind
Soil: must be well-drained
Uses: pollinator garden for bees and butterflies, garden borders, cut flowers, hummingbirds
Propagation: seeds, cuttings, root divisions
Pruning: cut off flower spikes after flowering, cut off faded foliage in fall and discard
Problems: All parts are toxic to animals and humans when ingested. Aphids, crown rot, slugs, botrytis grey mold, mildew, leaf miners
Comments: Delphiniums are one of my favorite perennials. Their narrow elegant profile, fern-like foliage, and spires of blue flowers are difficult to resist. In the garden, they provide a much-needed vertical accent for round, weeping, horizontal and vase shaped plants.
Persnickety plants: I wish delphiniums weren’t so finicky. Growing them in the Pacific Northwest is a bit tricky due to all the rain. Combine that with clay soil and plants inevitably rot. Delphiniums must have good drainage as they are prone to many types of diseases, especially crown and root rot. I’ve lost quite a few myself due to crown rot. To prevent diseases, plant them where there’s good air circulation and don’t overcrowd.
Garden location: Plant delphiniums in sunny location where they’ll receive 6 to 8 hours of sun per day. Morning sun is best, so morning dew quickly evaporates. Shelter from strong winds to prevent their flower stalks from flopping over. It’s best to keep them staked from the get-go. When stems bend, cut them back by one half so new growth will develop at the base. Place any flower spikes in a vase as delphiniums are excellent cut flowers.
Deadheading & Seeding: To ensure new generations and longevity, allow some seeds to develop. Delphinium’s seeds are viable and will grow into new plants, but don’t worry, they are not invasive. It is important to deadhead them after flowering so they don’t waste energy producing seeds, however, leave a few faded flower stalks so they will self-seed and will germinate the following spring.
Types of delphiniums: There are many varieties of delphiniums. The tallest varieties are found within the Delphinium elatum group, with stalks typically 5 to 6 feet tall with a spread of 2 feet. The majority of garden delphinium hybrids and cultivars are derived from the elatum species. The D. belladonna group averages 3 to 4 feet tall with a spread of 2 feet. Dwarf varieties, like D. grandiflorum, range 1 to 2-feet tall and 12 to 18 inches wide.
Annual delphiniums (Delphinium, Consolida) are commonly referred to as larkspurs. They resemble perennial delphiniums, but they do not regrow in spring. There are numerous types available with a wide range of colours. Purchase plants from plant nurseries in spring or grow them from seed.
Planting: Plant potted delphiniums in the spring. Improve existing soils by mixing in a couple of inches of compost, SeaSoil or composted manure. When planting, dig a hole in the amended soil at the same depth of the rootball and twice as wide. The crown, where the stems and roots meet, should be level with the soil.
Toxicity: All types of delphiniums, and their parts, are poisonous to animals and humans if ingested. Touching the plant can cause skin irritation with some people so it’s a good idea to wear gloves when handling them, including the annual species. FYI delphiniums are used in asthma medications.