Tall Larkspur is a herbaceous perennial growing from 2 to 6 feet in height on round smooth green stems, which may have reddish tints near the base.
The leaves are all stem leaves, deeply lobed into irregular segments. The lower stem leaves are on long stalks and divided into 5 parts, with each part having 3 to 7 lobes. These leaves can be almost as wide as long. The mid-stem leaves have fewer lobes and shorter stalks. There are no leaves in the upper 1/5 of the stem at flowering time.
The inflorescence is a panicle of stalked flowers, the central part of the panicle being the top of the main stem, the panicle side branches are much shorter There are 8 to 30+ flowers. Panicle stems and flower stalks all have fine hair.
Flowers: are bisexual and can range in color from whitish to pale lavender or purple. There are 5 sepals - the upper sepal spurred and the shape provides the common name of Larkspur, 2 lateral sepals that point forward and 2 lower. The lower and laterals having much the same ovate shape. There are 4 petals - 2 upper petals that are spurred and enclosed inside the upper sepal. The spurs are straight. Two lower petals are clawed and may have 2-lobed lips with many whitish hairs and these 2 petals usually cover the stamens. The spur of the flower is tilted no more than + or - 45º from the horizontal. There are 3 pistils with styles. Each flower stalk has a small linear green bract that has fine hair and is located only 2 to 4 mm from the flower.
Seed: Fertile flowers produce a dry 3-sectioned follicle (seed capsule) that contains numerous dark brown pyramidal seeds that have whitish winged margins (wings). Seeds require 60 days of cold stratification for germination.
Habitat: Tall Larkspur grows from a rhizomatous root systems that will usually produce several flowering stems. It needs fertile, well drained soils, medium to mesic moisture conditions and full sun but not in areas where it is extremely hot. Moderate amounts of shade are OK but the plants may lean a bit. These is some susceptibility to powdery mildew. Plants can be divided in early spring before growth starts and also grown from seed. The plant also self-seeds.
Names: The genus Delphinium has over 300 species in the world. The name is derived from the Greek delphinion which in turn is from delphin, and is thought to have been applied for the possible resemblance of the flowers of some species to classical Greek sculptures of dolphins. The species, exaltatum, means very tall. The author name for the plant classification, of 1789 - ‘Aiton’ is for William Aiton (1731-1793), Scottish botanist, who succeeded Philip Miller as superintendent of the Chelsea Physic Garden and then became director of Kew Gardens, where he published Hortus Kewensis, the Garden’s catalogue of plants.
Comparisons: The common name of Larkspur has been applied to all the Delphiniums due to the shape of the flower. Several Eurasian species have been introduced to North America and cultivated as ornamentals - these being your typical garden variety of Delphinium. The native species are not known to naturalize. With so many species, close comparison is needed to distinguish species. The native species that closely resembles Tall Larkspur is the Dwarf Larkspur, D. tricorne, but there the flower is always usually white and it blooms earlier in the summer. The single species of Delphinium that is native to Minnesota is D. carolinianum subsp. virescens, which also has white flowers, but less than 10, and is usually no more than 1 to 2+ feet high and the spur is tilted upward, sometimes 90º to the flower stalk.
Above: The flowering panicle of Tall Larkspur has the main stem as its tallest section. Flower color ranges from whitish to pale lavender or purple.
Below: The petals are small and enclosed within the sepals. The 2 upper petals have nectar spurs. The lower petals have whitish hairs which obscure the stamens.
Below: 1st photo - The side view shows the larger upper sepal with the long spur (the 'Larkspur'). The lateral sepals point forward and the two lower ones extend forward from the base. The tilt of the spur is never more than 45 degrees off the horizontal. Note the small linear bract on each flower stalk. 2nd photo - The 3-sectioned seed capsule has numerous pyramidal seeds with whitish winged margins.
Below: The lower stem leaves are on long stalks and, divided into 5 sections, each section with 3 to 7 lobes. The mid-stem leaves are simpler with shorter stalks.
Below: The root is rhizomatous, producing several flowering stems. The photo of the plant shows the simpler mid-stem leaves and the absence of leaves in the top part of the stem.
Tall Larkspur is native to a small group of states in the eastern U.S.: AL, KY, MD, ME, MO, NC, OH, PA, TN, VA and WV. In a number of these states it is considered endangered. It grows in most other states of the eastern half of the U. S. and seems to do well in the southern half of Minnesota in growing conditions explained above.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"