Agastache is a genus of aromatic herbaceous perennials in the mint family (Lamiaceae), commonly known as giant hyssops or hummingbird mints. Most taxonomic sources recognize about 22 species, although the GBIF backbone currently accepts 23. The genus belongs to the subfamily Nepetoideae and tribe Mentheae, and was established in 1762 by Jan Frederik Gronovius. The botanical name comes from the Ancient Greek ágan ("very much") and stákhus ("ear of grain"), a reference to the dense, showy flower spikes that crown the plants in summer.
Members of the genus are upright herbs ranging from about 0.5 to 3 metres tall, with stiff, four-angled stems clothed in opposite, toothed, lance-shaped leaves that are typically aromatic when crushed — releasing scents that variously evoke anise, licorice, mint, or root beer depending on species. Leaves measure 1–15 cm long and up to 11 cm wide. At stem tips, plants produce tall, dense, spike-like inflorescences of tubular, two-lipped (zygomorphic) flowers, with colours spanning white, yellow, orange, pink, mauve, red, and deep purple. The combination of nectar-rich tubular flowers and long bloom period makes Agastache one of the most pollinator-magnetic groups in the Lamiaceae.
The genus is centred on North America, with the bulk of species concentrated in the southwestern United States and northern Mexico; a single species, Agastache rugosa, is native to eastern Asia. Several species have escaped cultivation and become naturalized outside their native range, with records from Austria, Laos, and Vietnam. Within the genus, taxonomists recognize two sections — sect. Agastache, encompassing the temperate eastern-North-American and Asian species, and sect. Brittonastrum, covering the brightly coloured, hummingbird-pollinated species of the arid American Southwest. Synonyms applied historically to the genus include Brittonastrum, Flessera, Dekinia, and Lophanthus.
Etymology
The genus name Agastache derives from two Ancient Greek roots: ἄγαν (ágan), meaning "very much," and στάχυς (stákhus), meaning "ear of grain." The compound is a direct reference to the plants' tall, dense, spike-like inflorescences that rise above the foliage in summer. The genus was formally described in 1762 by the Dutch botanist Jan Frederik Gronovius, working from material collected by John Clayton — which is why the standard authorship cited by the GBIF backbone is "Clayton ex Gronov." In common English usage, Agastache species are called "giant hyssops" (in reference to their stately bloom spikes, though they are not true Hyssopus) or "hummingbird mints" (for the New World species that attract hummingbirds in the southwestern United States and Mexico).
Distribution
Agastache is overwhelmingly a New World genus. The majority of its species are native to North America, with the centre of diversity in the southwestern United States and northern Mexico, where the brightly coloured, tubular-flowered species of section Brittonastrum form a conspicuous element of montane and arid-region floras. A few temperate eastern-North-American species — notably A. foeniculum, A. nepetoides, A. scrophulariifolia, and A. urticifolia — extend the range north into the Great Plains and the boreal edge of Canada, with A. foeniculum reaching as far as the Arctic. A single species, A. rugosa, is native to eastern Asia (China, Korea, Japan). Beyond its native range, individual Agastache species have escaped cultivation and naturalized in Austria, Laos, and Vietnam.
Ecology
Agastache species are characterized by long-blooming, nectar-rich tubular flowers that make them exceptional pollinator plants. The genus attracts bees, butterflies, bumblebees, and — particularly in the case of the brightly coloured American species — hummingbirds, a relationship reflected in the common name "hummingbird mint." A. foeniculum is held in special regard by beekeepers: a single acre is reported to support up to 100 honey-bee hives, producing a light, fragrant honey, with bloom extending from June through frost. The genus's strongly aromatic foliage, which contains volatile essential oils typical of the Nepetoideae, makes plants notably resistant to browsing deer and rabbits.
Cultivation
Most cultivated Agastache species are grown in USDA hardiness zones 5–10, although hardiness varies dramatically across the genus: the prairie-native A. foeniculum is reported hardy to USDA zone 1, A. nepetoides, A. rugosa, A. scrophulariifolia, and A. urticifolia to zones 3–5, while the colourful southwestern hummingbird mints are best treated as short-lived perennials in colder zones. Plants demand full sun (six or more hours daily) and sharply drained soil — sandy, loamy, or even shallow rocky substrates suit them, and they tolerate acidic to neutral pH. The most consistent killer of cultivated Agastache is "wet winter feet" in poorly drained ground. Once established, plants are notably drought- and heat-tolerant and require little maintenance. Space plants 3–6 feet apart depending on cultivar; pest issues, though uncommon, can include spider mites, thrips, aphids, whitefly, and slugs. Numerous garden cultivars are widely grown, including 'Blue Fortune' (recipient of the Royal Horticultural Society Award of Garden Merit), 'Blue Boa,' 'Firebird,' 'Purple Haze,' and the Acapulco series.
Propagation
Agastache is straightforward to propagate by several methods. Seed is the most common route: seeds can be started indoors in early spring and transplanted out in late spring or early summer once frost risk has passed. Plants will also self-seed in optimal conditions. Vegetative propagation is equally reliable — established clumps can be divided in spring, and softwood stem cuttings root readily during the active growing season, which is particularly useful for preserving the floral characters of named cultivars that do not come true from seed.
Cultural uses
Agastache has a long record of human use that spans culinary, medicinal, and ornamental traditions. The leaves and flowers of A. foeniculum (anise hyssop) carry a sweet aniseed flavour and are used fresh in salads, brewed into tea, crumbled into potpourri, or used to season cooked dishes and acid fruits; PFAF notes that prolonged consumption can cause a dry mouth. The same species was used medicinally by the Cree, Cheyenne, and Ojibwa peoples to treat fevers, respiratory complaints, and burns, and herbals describe its leaves as cardiac and diaphoretic, with infusions traditionally given for colds, fevers, and weak-heart conditions and poultices applied to burns. In Asia, A. rugosa (huoxiang, 藿香) has a long-standing role in Chinese herbology. Across the genus, the aromatic foliage of nearly all species supports use as flavouring tea or potpourri.
Taxonomy notes
Agastache is placed in the mint family (Lamiaceae), subfamily Nepetoideae, tribe Mentheae. The genus was established in 1762 by Jan Frederik Gronovius, with the standard authorship cited as "Clayton ex Gronov." Within the genus, taxonomists recognize two sections: sect. Agastache, holding the temperate eastern-North-American and East-Asian species, and sect. Brittonastrum, which encompasses the brightly coloured, narrow-tubed, hummingbird-pollinated species of the American Southwest and Mexico. Historical synonyms at the genus level include Brittonastrum, Flessera, Dekinia, and Lophanthus. Species totals vary slightly across authorities: Wikipedia, NCSU, and SEINet each give 22 species, while the current GBIF backbone lists 23 accepted species; the GBIF taxon record additionally reports roughly 51 descendant taxa once infraspecies and synonyms are included.
Conservation
No species of Agastache is currently listed in the IUCN Global Invasive Species Database, and the genus is not flagged as a global invasive concern. Several individual species, however, have naturalized beyond their native ranges — notably in parts of Europe and Southeast Asia — but without rising to invasive-species status. Conservation status of individual species varies and is not summarized at genus level by any consulted source.
