This year’s Herb of the Year, so named by the International Herb Association, is anise-hyssop (Agastache foeniculum), also called giant hyssop or blue giant hyssop. Or just agastache (ah-guh-STAK-ee).
The name Agastache (ah-guh-STAK-ee), from Greek, means many (“agan”) spikes (“stachys”), referring to the plant’s numerous flower spikes. As for foeniculum, it refers to another herb, fennel, and the fennel-like taste of the plant.
Certainly not one of the more common culinary and medicinal herbs, anise-hyssop is a rather short-lived but easy-to-grow perennial of the mint family (Lamiaceae) and, in fact, not really all that much like rather shrubby true hyssop (Hyssopus officinalis), itself also fairly obscure, either in form or flavor. Tastewise, anise-hyssop has an anise-like flavor sometimes likened to that of French tarragon (Artemisia dracunculus sativa).
Anise-hyssop is an attractive plant, forming a clump of upright stems bearing oval toothed leaves whitish underneath, each topped by a dense spike of lavender-purple flowers (there is also a white-flowered form, ‘Alabaster’) that bloom on and on all summer, from June to September in the Northern Hemisphere. It’s attractive to bees as well: they love agastaches of all kinds and buzz constantly around the flowers. Giant hyssop is a great choice for honey production as well.
Hummingbirds also visit the flowers (when the bees aren’t around) as do butterflies. The plant’s licoricelike odor, however, seems to discourage deer, rabbits and other mammals and they leave it alone.
Given its height, usually about 4 to 5 feet (120–150 cm), anise-hyssop is probably most useful not in the herb garden, where it might shade out its smaller neighbors, but in the back of the flower bed, where its generous, summer-long bloom will be most appreciated.
Anise-hyssop is both a culinary and medicinal herb. In the kitchen, both the flowers and leaves are used as a seasoning and in teas, syrups and salads, sometimes as a substitute for tarragon. If you need a quick breath freshener, munch on a few leaves of its leaves. Dried, the leaves and flowers can be stored for future culinary use or added to potpourris. Medicinally, this eastern and central North American native was used by native peoples to treat wounds, fevers, coughs and diarrhea.
Giving its obscurity, you’re probably not going to find this plant in your local garden center. Instead, look to specialized herb nurseries for plants, local ones perhaps, otherwise mail order. Seed is easier to find and offered by many mail-order sources that sell herb seeds.
Starting seed indoors for bloom the first year is possible, but complicated, since it requires a very early start: midwinter (late January or earliest February in the Northern Hemisphere). Since light levels at that season are very low due to short winter days, you’d probably need supplementary lighting to bring this off. The alternative is to start the seeds indoors about 4 to 6 weeks before last frost or even just to sow them outdoors and then to grow them just for their leaves alone the first year, leaving flowering to year two.
Plant in full sun or partial shade, in a fairly rich, slightly acid to neutral, moist but well-drained soil, setting plants about 18 inches (45 cm) apart.
Once established, Anise-hyssop is quite drought resistant, but it does much better under moist conditions. It’s extremely hardy, to USDA hardiness zone 1, and prefers cool summers and cold winters. As such, it’s not a good choice for warm-winter areas (zones 9 and above). Where summers are hot, do keep it moist.
As time goes on, the base of the plant becomes woody and the plant dies out. Calculate it will be good for about 3 years, then you’ll have to start it anew. Or, more likely, you’ll be able to pick a few to keep from its among numerous seed-grown offspring, as it self-sows generously and can be quite weedy. (Mulching would be a good way of keeping the mother plant moist while preventing excessive self-sowing.)
You can also readily propagate anise-hyssop by stem cuttings.
Anise-hyssop is far from the only species of Agastache of interest to gardeners.
Very similar to Anise-hyssop and just as floriferous and useful is Korean mint or purple giant hyssop (A. rugosa), zone 5. A bit shorter, it reaches 3 to 4 feet (90 to 120 cm) tall with dense spikes of lavender-blue flowers. Native throughout temperate eastern Asia, you can think of it as an Asian version of the American A. foeniculum, with a more mint-like scent. As you might expect given its origin, it’s most commonly used in Asian cooking.
A. rugosa ‘Honey Bee Blue’ is similar to the species, with the same lavender-blue flowers, but is shorter: 2–3 feet (60–90 cm). ‘Honey Bee White’ is a white-flowered version of the same. A. rugosa ‘Little Adder’ is even shorter: 16–18 inches (40–45 cm). It too has lavender-blue flowers. All three bloom all summer and all are just as useful as edible and medicinal plants as ornamentals.
Korean mint also gave rise to a popular cultivar with chartreuse-yellow leaves, A. rugosa ‘Golden Jubilee’, an All-America Selections winner for 2003. About 20 inches (50 cm) tall, it’s just as floriferous as the species, but its lime-yellow leaves contain less chlorophyll, so give it full sun. Watch out, though, it does self-sow prolifically. Since it is true-to-type from seed, the seedlings will be chartreuse green and easy to spot if you need to cull or move them. Zone 5.
Another close relative is yellow giant hyssop (A. nepetoides). It’s much bigger than A. foeniculum (up to 9 feet/3 m, although usually no more than 6 feet/2 m), but with pale greenish-yellow to whitish flowers rather sparsely born on green spikes, making it of lesser ornamental value. Although it is not highly scented, it’s used medicinally, notably as a wash in treating poison ivy, and bees still adore it. This eastern North American native is very hardy, to zone 2.
Probably the best anise-hyssop for laidback gardeners are the sterile hybrids, usually just called agastaches. Most are crosses between A. foeniculum and A.rugosa and produce no fertile seed, so there’ll be no annoying self-sown seedlings to cull.
A. ‘Blue Fortune’, with lavender-blue spikes produced all season, is the best known and indeed, really an outstanding plant. About 2 to 3 feet (60-90 cm) tall, it’s a real charmer in the middle of the flower border and just doesn’t stop blooming. Be forewarned of its short-lived nature, though, and don’t forget to start it anew from cuttings every 3 years. Zone 4
Others to try are A.‘Blue Boa’ (thick spikes of deep, violet-blue flowers, zone 5) and ‘Black Adder’ (pinkish-lavender flowers arising from deep purple bracts, zone 5).
And Now for Something Completely Different
In a totally different category are the so-called hummingbird mints (A. cana, A. aurantiaca, A. ruprestris and others), with red, orange, pink or purple flowers on much shorter, smaller leaved plants. Native to the North American Southwest, they’re better adapted to dry climates and hot summers and are not very hardy (zone 7, possibly 6 in very well-drained soil). They are also used medicinally and in cooking, but are definitely more minty than anise-like. They’re becoming quite popular as ornamental annuals or, where they are hardy, short-lived perennials.
Whether you call the different species anise-hyssop, giant hyssop, Korean mint, hummingbird mint or just agastache, Agastachespecies are certainly worth discovering as the 2019 Herb of the Year.