Delphinium exaltatum Aiton

Nomenclature

Delphinium exaltatum, commonly called tall larkspur, is a flowering plant species in the genus Delphinium of the buttercup family. Note that other Delphinium species, such as Delphinium barbeyi, are also commonly referred to as tall larkspur.

Native Distribution

D. exaltatum is native to the central and eastern United States, where it occurs in Kentucky, Maine, Ohio, Pennsylvania, Maryland, West Virginia, Virginia, North Carolina, Alabama, Tennessee, and Missouri.

Growth Form

It is a perennial herb that grows a stem up to 2 metres (6.6 ft) tall from a long, thick taproot. The base of the stem may have a reddish tinge, and the stem loses all leaves by the time the plant blooms.

Leaf Structure

Its leaves are roughly circular or pentagonal in overall shape, divided into several wedge-shaped lobes. Each leaf blade grows on a petiole that can reach up to 15 centimeters long.

Flowering Period

Flowering occurs between July and September.

Inflorescence Structure

The inflorescence is a raceme holding up to 30 flowers. The sepals range in shade from dull blue to purple or lavender, and occasionally they are white.

Fruit Characteristics

The fruit is a follicle approximately one centimeter long.

Habitat Types

This species grows in wooded areas and prairie habitat, and tolerates both sunny and shady locations. It can grow on slopes facing any direction.

Substrate Preferences

Its growing substrate is often rocky, typically containing calcareous stone such as limestone, and sometimes chert. It may also grow on amphibolite or diabase.

Disturbance Tolerance

It can tolerate a certain level of disturbance, and persists in disturbed habitat remnants including road cuts, ditches, fence rows, and fields.

Associated Plant Species

Recorded associated plant species vary by location: upland boneset (Eupatorium sessilifolium) and staghorn sumac (Rhus typhina) in Maryland; barren strawberry (Waldsteinia fragarioides), fourleaf milkweed (Asclepias quadrifolia), eastern leatherwood (Dirca palustris), and prairie trillium (Trillium recurvatum) in Missouri; upland bentgrass (Agrostis perennans), orchard grass (Dactylis glomerata), mountain oatgrass (Danthonia compressa), Philadelphia lily (Lilium philadelphicum), timothy-grass (Phleum pratense), three-toothed cinquefoil (Sibbaldiopsis tridentata), and self-heal (Prunella vulgaris) in North Carolina; eastern green violet (Hybanthus concolor), American bladdernut (Staphylea trifolia), and yellow horse gentian (Triosteum angustifolium) in Pennsylvania; and barrelhead gayfeather (Liatris cylindracea), Chinese bushclover (Lespedeza cuneata), smooth aster (Symphyotrichum laeve), eastern smooth beardtongue (Penstemon laevigatus), downy skullcap (Scutellaria incana), and hoary puccoon (Lithospermum canescens) in Tennessee.

Toxicity

Like most other Delphinium species, D. exaltatum is toxic, containing multiple poisonous alkaloids. Every part of the plant is poisonous, with seeds being the most toxic part.

Population Status

This species can be found across many areas of the eastern half of the United States, with over 100 documented occurrences; however, most populations are small, containing no more than 50 individuals.

Habitat Loss Threat

The main threat to the species is habitat loss. Agriculture and development have destroyed much of its suitable habitat.

Fire Suppression Threat

Fire suppression is also a threat; the loss of the natural fire regime allows competing vegetation to overgrow and encroach, displacing this native plant.

Additional Threats

In some areas, livestock causes habitat disturbance such as soil compaction. Additional contributing threats include road building, quarrying, and logging.

Pollinator Threat

Pesticide use can reduce populations of the insect pollinators that this species relies on. While D. exaltatum can tolerate some level of disturbance, as seen in its ability to grow successfully along roadsides, it cannot survive full habitat destruction.

Vegetation Management

Current conservation management activities for D. exaltatum include controlled burns and other methods to clear excess competing vegetation. Protection of its insect pollinators is also recommended.

Habitat Protection

Suitable habitat should be preserved, and destructive activities such as logging, grazing, and road construction should be excluded from these areas.

Transplantation Efforts

Transplanting propagated D. exaltatum individuals into existing suitable habitat has been successful.