Posted by Aaron Barton on Apr 6th 2023

Agastache (Anise Hyssop)

Exploding in a sea of light purple-blue blooms buzzing with delighted pollinators all season long, Agastache foeniculum (ah-GAH-sta-kee fin-ICK-yoo-lum), commonly known as anise hyssop, is a versatile Minnesota native plant well-suited for the home landscape. A member of the mint family, Lamiaceae, anise hyssop produces upright square stems and aromatic, anise-scented foliage, maturing to an incredibly lush upright mound of foliage of up to 48” tall and 24-36” wide, spreading gently by rhizome to form attractive clusters in the landscape. Stems are accented with broad, lance-like light green opposite leaves up to four inches long with sharply toothed margins and dusty green undersides covered in fine hairs, densely lining stems for an exceptionally verdant appearance to contrast their abundant flower spikes.

Blooming throughout the summer for weeks on end, anise hyssop explodes in a sea of color, prolifically producing terminal spikes up to six inches long flush with tubular, nectar-rich lavender purple flowers densely arranged in verticillasters, or false whorls, appearing as a cohesive cluster, yet truly composed of two opposite cymes of numerous blooms—a signature trait of the mint family. Swarming with pollinators, including hummingbirds, their tubular, two-lipped flowers reach up to a third of an inch long, with four lavender stamens topped with purple anthers, as well as purple calyxes that offer lasting color well into the early fall, even after blooms begin to fade. Plants will also benefit from regular deadheading to promote dense regrowth and the production of additional flower spikes.

Agastache thrives in full sun areas in moist, well-drained soils, is drought tolerant after establishing a deep tap root system, and is generally unbothered by deer or rabbit feeding because of their lovely anise-scented foliage. Avoid over-mulching anise hyssop and ensure sites are well-drained even throughout the winter, however, as plants are prone to root rot in consistently wet and poorly drained areas, especially when dormant.

Though a typically shorter-lived perennial, lasting for three to five years on average, plants are durable, fast growers and will readily seed to continue thriving in the garden if conditions are favorable, needing light to germinate. Plants can also be split easily in the spring or fall, just be sure to water new transplants thoroughly. A phenomenal, low maintenance plant that is worth replanting from time to time, anise hyssop is exceptional in pollinator gardens, rain gardens, cottage gardens, natural landscapes, sunny borders, sensory gardens, and background plantings, especially when mass planted, and is great in floral arrangements as well.

Unfortunately, the closely related, visually similar, non-native Korean Hyssop, Agastache rugosa, is increasingly mislabeled as native Agastache foeniculum, posing a threat to native anise hyssop due to hybridization and seed source contamination, with plants seeding and spreading prolifically once planted. This problem has been of special concern here in Minnesota lately, and gardeners should ensure they have the correct species, though we strive to only carry the true native as labeled here at Tonkadale. True native anise hyssop leaves should end in a sharp point, will be more slender than round in shape, have fine, sharply toothed margins, not more open, rounded toothing, will be dusty green in color on the undersides of leaves due to soft dense hairs, not sparsely hairy with coarse hair mostly concentrated along leaf margins along with circular markings or areoles, and will have a green flower base, not a purple base.

Happy planting!