Description: This native perennial plant is 2-4’ tall, branching occasionally near the apex. The four-angled stems are glabrous or slightly pubescent. The opposite leaves are up to 4" long and 2" across, and have short petioles. They are cordate or broadly lanceolate, with crenate margins. The upper surface of the leaves is conspicuously veined and dull green, while the lower surface is white and finely canescent. The foliage has an anise scent. The upper stems terminate in spikes of flowers about 3-6" long. The small flowers are arranged in dense whorls that are crowded along the spike, although sometimes the whorls are less crowded and more interrupted. The calyx of a flower is tubular and has five teeth; it is usually dull blue-violet or a similar color, becoming more colorful toward its tips. The tubular flowers are about 1/3" long, extending beyond the calyx. They are blue-violet. The corolla of a flower is divided into a short upper lip and a longer lower lip. The lower lip has 2 small lateral lobes and a larger central lobe. Exerted from the throat of the flower are 4 stamens with blue-violet anthers, and a style that is cleft toward its tip. The flowers bloom in scattered locations along the spikes for about 1-2 months from mid- to late summer. During this time, calyx of each flower remains somewhat colorful. There is no floral scent. The flowers are replaced by nutlets that oval-shaped and smooth. The root system produces a taproot.
Cultivation: The preference is full or partial sun, and mesic to dry conditions. The soil can consist of loam, clay-loam, or contain some rocky material. Foliar disease isn’t a significant problem, although some of the lower leaves may drop from the central stem in response to a drought. Occasionally, slugs and insects will feed on the leaves, creating holes. This member of the Mint family is more resistant to drought than many others.
Range & Habitat: In the wild, Anise Hyssop is rare in Illinois; it is known to occur in only Menard county in central Illinois (see Distribution Map). This species is more common in areas that lie northwest of Illinois. Typical habitats include openings in dry upland forests, upland areas of prairies, scrubby barrens,Underside of Leaf and thickets. Cultivated forms of Anise Hyssop are often grown in flower gardens; these cultivars are often hybrids and vary in their fidelity to the wild forms of this plant. Outside of Menard county, populations in the wild are likely to be plants that have escaped cultivation.
Faunal Associations: The flowers are pollinated primarily by honeybees, bumblebees, and other long-tongued bees, which seek nectar or pollen. The flowers are also visited by an oligolectic bee, Doufourea monardae, which has extended its range into Illinois. Other occasional visitors are Green Metallic bees, bee flies, and various butterflies. Mammalian herbivores normally avoid consumption of this plant, as the anise scent of the foliage is repugnant to them. The anise scent may also deter some leaf-chewing insect species.
Comments: Because of its rarity, Anise Hyssop is not normally thought of as a prairie species in Illinois, nor does it appear in many field guides of prairie plants for the tallgrass prairie. This plant does occur in the northwestern area of the tallgrass prairie, however, with a few scattered remnant populations elsewhere. Other members of this genus are woodland species. One of them, Agastache scrophulariaefolia (Purple Giant Hyssop), has flowers with similar coloration to Anise Hyssop. However, the foliage of Purple Giant Hyssop doesn’t have an anise scent and the the undersides of the leaves are green, rather than white. Purple Giant Hyssop is more pubescent or hairier than Anise Hyssop, and it tends to be a taller plant. The calyx of each flower remains green for this species, unlike Anise Hyssop, where each calyx assumes a coloration that is more similar to the flowers. This latter characteristic can cause Anise Hyssop to look like it is in flower, even when it is not.