Plants of the Eloise Butler Wildflower Garden

Blue Giant Hyssop is an erect native perennial forb growing from 2 to 4 feet high on sturdy green 4-angled stems. Stems occasionally branch near the top and can be with or without stem hair.

The leaves are opposite, somewhat triangular with coarse teeth, medium green, with prominent veining and mostly on short stalks. The leaf underside is whitish with fine hair. The base varies from wedge shaped to slightly heart-shaped. Teeth on large lower leaves may be somewhat rounded. Leaves have anise scent when crushed or brushed.

The inflorescence is a dense spike, up to 8 inches high, of flowers arranged in what looks like a number of whorls at the top of stem, sometimes interrupted as shown in the photo below. In the mint family this arrangement is called a 'verticillaster' where the flowers look like a whorl arrangement but are actually in cymes that rise from the axils of a pair of opposite stem bracts. The spike has a number of bract nodes and thus a number of verticillasters, but they are closely spaced and you seldom see any interruptions. Large plants can produce many spikes from the upper leaf axils. Flowers open in various spots around the spike on the various verticillasters, not from the bottom of the spike to the top. The flowers are very aromatic with an anise scent.

The small flowers are 5-parted, about 1/3 inch long with a calyx that forms a tube with 5 sharply pointed teeth. The tube ranges from light blue to violet in color with the upper part the darkest. Several darker vein lines are often visible on the calyx. The corolla is similar in color but much lighter and slightly longer than the calyx. The lips of the corolla end with two lobes on top formed from 2 fused petals and three lobes on the bottom formed from three fused petals. Protruding from the corolla are 4 stamens with white filaments and violet-purple anthers and a single white style with a bifurcated tip. The stamens are in pairs of different length. Very delicate purplish vein lines are seen inside the corolla throat. Flower clusters in the spike are interceded with pairs of ovate light green floral bracts from which the cluster (the verticillaster) arises. Many species of bees are attracted to the flowers.

Seed: Fertile flowers produce a dry nutlet containing one oblong brown seed about 1 mm x 2 mm. These disperse by wind shaking the stem. Seeds are small and need light for germination plus 30 days of cold stratification. Seeds that fall from the plant will readily self-germinate in the Spring and the seedlings transplant easily and larger ones will flower the same year. American Goldfinches are quite fond of the seeds, even in the green stage.

Habitat: Blue Giant Hyssop grows best in sandy to loamy soils in full to partial sun with mesic to dry-mesic moisture conditions. The fibrous root system produces a small taproot, but no stolons. Good specimens are found in the Upland Garden on Prairie Path. It is generally available from nurseries that supply native plants.

Names: The common names are referring to "fragrant" and "anise" because the leaves have a fragrant anise odor when crushed, green or dry. The genus Agastache is derived from two Greek words - agan, meaning 'very much' and stachys, meaning 'an ear of wheat' which together refer to the flower spikes of this genus having many flowers, like grains of wheat. The species foeniculum, is from the the Latin word for Fennel, used here to represent a plant that produces a fragrant scent.

The author names for the plant classification cover two people; first ‘(Pursh)’ is for Frederick Traugott Pursh (1774-1820) German-American botanist who wrote A Systematic Arrangement and Description of the Plants of North America, and was the botanist who catalogued and described the plants brought back by the exploring expedition of Lewis and Clark. Pursh was disliked by American botanists because he took some of these plants to New York with him and later to London treating them as his own property. He did the same years later with much material collected by Thomas Nuttall, writing it up with no credit to Nuttall. Prush's work was revised by Otto Kuntze (1843-1907) German botanist, who edited the collections in Berlin and Kew Gardens and then published Revisio Generum Plantarum which laid out new rules for nomenclature which were ejected at the time by his peers but some acceptance came long after his death. An older scientific name for this species is A. anethiodora.

Comparisons: A similar looking plant but taller, and whose flowers have a green calyx is Purple Giant Hyssop, A. scrophulariifolia. That plant's roots produce stolons allowing it to reproduce that way. Another is Yellow Giant Hyssop, Agastache nepetoides, which is also tall, branched, produces stolons, but has yellow flowers and a catnip odor.