These are tall mints with stout sharply square stems. Our species are all known in cultivation. The flowers, especially in A. foeniculum, may appear nearly regular.
1. Leaf blades whitened beneath with fine dense felt-like pubescence; mostly in dry, open habitats.
1. Leaf blades green beneath, not hidden by pubescence (individual hairs visible); forests and forest edges, less often in open (and then usually moist) habitats.
2. Flowers blue; calyx lobes finely pubescent; rare introduction.
2. Flowers yellowish or rosy to purplish; calyx lobes glabrous or sparsely pubescent; native forest and moist meadow species.
3. Stems glabrous or minutely pubescent with short curved hairs on middle internodes; leaf blades pubescent with fine short hairs over entire surface beneath; calyx lobes at anthesis all less than 2 mm long.
3. Stems usually with at least a few long ± spreading hairs on middle internodes, especially on the angles; leaf blades pubescent with long hairs mainly on the veins beneath; calyx lobes at anthesis averaging at least 2 mm long.
All species found in Agastache
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. May 21, 2019. https://www.michiganflora.net/genus.aspx?id=Agastache.