Agastache: Fragrant Foliage and Colorful Blooms
My passion for the genus Agastache (pronounced ag-ah-STACK-key) began decades ago in the herb garden of a friend. She pointed out Agastache foeniculum, commonly called anise hyssop, and made me rub the coarse leaves to release their pungent aroma, which was mintlike, with hints of licorice and citrus. It came as no surprise to me to learn that the fresh and dried leaves of the plant are used as a food seasoning and for making tea.
While the leaf fragrance was memorable that day, I was even more taken by the herb's elegant upright habit and dense spikes of powder-blue flowers. Here was another good herb that could escape from the utilitarian herb garden to the ornamental perennial border. My friend further encouraged me to nibble on some flowers, which she described as tasting of a good frosted mug of Stewart's root beer. I agreed, and from that moment on, Agastache foeniculum became the "root beer plant" to me.
Ever since perennials took the garden world by storm in the 1990s, other worthy species and hybrids of Agastache have come to my attention. Like anise hyssop, they all produce wonderful pungent foliage and bear dainty, tubular flowers on dense spikes from midsummer until first frost. But many are quite different in appearance from A. foeniculum, most notably in their flower color and leaf size and shape. The range of flower colors is especially impressive, reminding me of a dessert tray of passion fruit, peach, orange, and raspberry sorbets, as well as other flavors in between.
As if beautiful form, color, and aroma weren't enough to recommend Agastache, the genus is also a magnet for wildlife. Bees, butterflies, and hummingbirds love to drink from the nectar-rich flowers. Hummers are highly attracted to red, orange, and pink-flowered forms, while butterflies, particularly swallowtails, favor the blue-flowered varieties.
The greatest concentration of Agastache species occurs in the southwestern United States and northern Mexico. The rest are scattered across the U.S., Europe, and Asia. The genus is part of the Lamiaceae, or mint family, which accounts for its square stems and aromatic foliage. In northern climate zones, most Agastache species are tender perennials—they sometimes winter over but do not seem to be long-lived in the garden. Southwestern species (A. aurantiaca, A. cana, A. rupestris) endure very dry conditions and poor, well-drained soils in their native habitat, but most of these adapt to richer, organic soils and wetter summers and winters in other regions of the country.
Plant Agastache in full sun to light shade in fertile, well-drained garden soil. If you periodically deadhead spent flower spikes, you'll extend bloom by preventing seed set. To coax winter hardiness in my northeastern garden in USDA Hardiness Zone 5, I leave the leaf and flower stems on the plants over the winter. In April, I cut the dead stems off about four to five inches above ground and hope and patiently wait for new growth—I am sometimes rewarded if the winter hasn't been too severe. I encourage adventurous gardeners in regions with wet, cold winters similar to mine to plant the southwestern species on sunny south- or west-facing slopes or in raised beds with sandy, fast-draining soil. The plant's crown should be planted high and then mulched with crushed gravel to encourage drainage away from the plant and to absorb heat on sunny winter days.
Agastache is relatively free of pests and diseases, with the exception of powdery mildew, rust, and other fungal pathogens that can affect the leaves during hot, humid weather if air circulation is poor. Plants can be propagated from spring division or sown from seed in early spring at soil temperatures of 55°F to 65°F. Root semiripe cuttings in either spring or late summer.
The Agastache A-List
I continue to test Agastache species and hybrids available in the marketplace in my New York Hudson Valley garden and nursery. Here are my recommendations for adventurous gardeners—see what you think.
Agastache cana (hummingbird's mint; wild hyssop)
The prolific raspberry-pink flowers of A. cana are truly the color of Häagen Dazs raspberry sorbet and are adored by hummingbirds. Native to the mountains of southern New Mexico and western Texas, this species produces two- to three-foot-tall flower spikes that wave and cavort happily in the summer border. Zones 5 to 9.
Agastache rugosa (Korean hyssop; wrinkled giant hyssop)
This species was originally collected in Korea by plant explorer Dan Hinkley of Heronswood Nursery fame and has proven to be very gardenworthy. Its two-inch triangular leaves are handsome deep green with a hint of purple beneath, and they exude a strong mint fragrance. Stunning deep violet-blue flowers bloom atop two-foot stems all summer and fall. This East Asian species is well adapted to wet temperate climates. Zones 5 to 9.
Agastache rupestris (sunset hyssop)
I love this Agastache for its narrow, fine-cut, gray-green leaves, soft texture, and salmon-colored flowers. True to the genus, its leaves emit a pungent, spicy fragrance. A three-foot-tall rugged plant, it can endure very dry conditions once established. Zones 5 to 9.
Agastache 'Blue Fortune'
A hybrid of A. foeniculum and A. rugosa, this robust nonstop bloomer is probably the hardiest Agastache and one of the best butterfly feeding stations in the garden. Its fat, five-inch-long spikes of powder-blue flowers perch atop three-foot stems. The two- to three-inch, toothed green leaves are strongly licorice-scented. Zones 6 to 10.
Agastache x 'Desert Sunrise'
High Country Gardens in Santa Fe, New Mexico, introduced this great Agastache (a hybrid of A. rupestris and A. cana) to gardeners. Flower spikes are the color of, you guessed it, a desert sunrise—blending shades of orange, pink, and lavender. This sturdy Agastache is the tallest in the group, reaching up to four feet. It adapts well to both dry and normal garden conditions and is a favorite of hummingbirds. Zones 5 to 10.
Aptly named for its fruit-scented foliage, 'Tutti-Frutti' sports showstopping raspberry-red flowers on slender two- to three-foot stems. A hybrid of A. barberi and A. mexicana (two other gardenworthy natives), it adapts well to container culture and will attract hummingbirds right to your doorstep. Zones 7 to 10.
Bedfellows and Companions
Whether grown as an annual or perennial, Agastache is incredibly floriferous in the garden and a great mixer and filler in summer and fall borders, containers, and flower arrangements (it's a great cut flower!). I like to combine it with other perennials of similar habit and continuous summer bloom like salvias (Salvia verticillata 'Purple Rain', S. x 'Scarlet Spires', or S. guaranitica 'Argentine Skies'), catmints (Nepeta sibirica 'Souvenir d'Andre Chaudron' or N. racemosa 'Walker's Low') and yarrows (Achillea 'Summer Pastels', A. 'Feuerland', or A. 'Anblo'). Ornamental oregano (Origanum 'Rosenkuppel') and red-hot pokers (Kniphofia 'Little Maid', K. 'Bees' Sunset', or K. 'Strawberries and Cream') make good bedfellows as well.
Perennials with gray foliage like Artemisia 'Powis Castle', silvery-white stems like Russian sage (Perovskia 'Longin'), and burgundy foliage like Euphorbia dulcis 'Chameleon' or Aster lateriflorus 'Lady in Black' provide nice contrast and background to the sorbet colors of Agastache in bloom. A clumping ornamental grass like blue oat grass (Helictotrichon sempervirens), the copper-red Pennisetum setaceum 'Rubrum', or a companion herb like rosemary (Rosmarinus officinalis 'Tuscan Blue') provide spiky form and vertical rhythm to complement Agastache.
Since Agastache continues to bloom profusely until frost, consider combinations with fall-blooming asters (Aster laevis 'Bluebird', A. oblongifolius 'Raydon's Favorite', or Aster novae-angliae 'Purple Dome') or goldenrod (Solidago rugosa 'Fireworks').
Don't forget that Agastache is also a terrific plant for pots and containers and mixes nicely with annuals and tender perennials such as Angelonia, Plectranthus species, Strobilanthes dyeriana, Alternanthera polygonoides 'Purple Select', and many cultivars of coleus (Solenostemon).
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