Tall larkspur (Delphinium exaltatum) is an herbaceous perennial native to the eastern US, ranging from Pennsylvania south to West Virginia and across to Tennessee and into Ohio. Its distribution also includes Maine but not the other New England states or New Jersey. Hardy between USDA zones 5 and 7, it is a member of the Buttercup family (Ranunculaceae), which means that all parts of the plant are poisonous.
California and the southwest (AZ, NM, UT, CO, WY) have native larkspurs as well that as expected, are adapted to the drier conditions typical of these regions. These native larkspurs include the sky blue larkspur (D. parishii) and sub-alpine larkspur (D. barbeyi) respectively.
The beautiful bluish-purple flowers of tall larkspur bloom July through September. The fragrant flowers attract butterflies and are up to 1-inch in size with a distinctive spur, hence the name larkspur. Tall larkspur grows best in full sun with well-drained fertile soils. Of note is that it better tolerates hot, humid conditions in the south than most of the Delphinium hybrids. Tall larkspur is susceptible to powdery mildew, botrytis blight, leaf spots and crown rot.
As one might guess from the name, tall larkspur is a tall flower reaching 4 to 6 feet in height. Although tall larkspur has more foliage than other native larkspurs, it has a somewhat lanky appearance so it’s best planted in combination with other plants in the perennial border or along a woodland edge.
It is listed as endangered in Maryland, Pennsylvania, and Tennessee and of special concern and endangered in North Carolina.