About Delphinium exaltatum Aiton
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. 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. 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. 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 occurs between July and September. 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. The fruit is a follicle approximately one centimeter long. This species grows in wooded areas and prairie habitat, and tolerates both sunny and shady locations. It can grow on slopes facing any direction. Its growing substrate is often rocky, typically containing calcareous stone such as limestone, and sometimes chert. It may also grow on amphibolite or diabase. It can tolerate a certain level of disturbance, and persists in disturbed habitat remnants including road cuts, ditches, fence rows, and fields. 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. 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. 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. The main threat to the species is habitat loss. Agriculture and development have destroyed much of its suitable habitat. Fire suppression is also a threat; the loss of the natural fire regime allows competing vegetation to overgrow and encroach, displacing this native plant. In some areas, livestock causes habitat disturbance such as soil compaction. Additional contributing threats include road building, quarrying, and logging. 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. 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. Suitable habitat should be preserved, and destructive activities such as logging, grazing, and road construction should be excluded from these areas. Transplanting propagated D. exaltatum individuals into existing suitable habitat has been successful.
