When to Plant Agastache: Spring or Early Fall Planting, Seed Stratification and Drainage for Anise Hyssop and Hummingbird Mint

Agastache is a genus of about 22 species in the mint family, most native to North America; many garden kinds come from the Southwest and Mexico, with a smaller group from Asia (NC State). The common names cover several of them: anise hyssop (A. foeniculum) is a prairie and Midwest native, hummingbird mint and sunset hyssop (A. rupestris) come from the Southwest, and Korean mint (A. rugosa) is from East Asia (NC State). Wisconsin points out that anise hyssop is not closely related to true hyssop or to anise; the name comes from its anise-scented leaves, which the Almanac and NC State say are used in teas.

When to plant agastache

Use our planting calendar to find your last spring frost and count back 6 to 8 weeks for an indoor start. Wisconsin says anise hyssop grown from seed often blooms in its first year, so a spring start still gives you flowers by late summer.

How to plant agastache

Ask Extension warns against spots where downspouts or snowmelt collect. In clay, our reading is to plant on a slight mound or in a raised bed so water drains away from the crown, which is what NC State's raised-bed advice amounts to.

Watering, feeding and deadheading

• Water weekly until established, then rarely (Almanac). NC State calls the genus heat and drought tolerant.
• Go easy on food. The Almanac adds only a thin layer of compost every year or two.
• Deadhead for more flowers (Wisconsin, Almanac). NC State says deadheading sunset hyssop after the first flush encourages fall blooms.
• Leave the last seed heads for birds; Wisconsin says goldfinches eat the seed, and the Almanac leaves the final flowers standing.
• Expect volunteers. Anise hyssop self-sows readily, but Wisconsin says the seedlings are easy to pull.
• Trim leggy plants in spring by up to a third (Almanac).

Agastache in containers

NC State suggests containers as one way to give agastache the drainage it needs, and the Almanac uses a pot at least 12 inches wide and deep. Ask Extension notes the trade-off: a pot lets you control drainage but exposes roots to more freezing and thawing than the ground does. Our reading is to use a gritty, free-draining mix, keep the saucer empty and move pots against a sheltered wall in winter.

Fall and winter

• Plant fall transplants early so roots establish before the ground freezes (Ask Extension).
• Keep the crown dry. Anise hyssop overwinters well in well-drained soil but gets crown and root rot in wet ground (NC State), and 'Black Adder' and sunset hyssop will not survive winter in wet, heavy soil (NC State).
• Expect a short life. Wisconsin calls anise hyssop a short-lived perennial, and NC State tags Korean mint the same way, so let a few seedlings grow on as replacements.

Pests and problems

NC State lists spider mites, thrips, aphids, whiteflies and slugs for the genus, and rust, powdery mildew and leaf spots for anise hyssop. Wisconsin and the Almanac tie mildew to humid weather, overhead watering and crowding, so space plants and water at the base. NC State calls the genus deer and rabbit resistant, but Wisconsin says rabbits do eat anise hyssop while deer don't favor it.

Agastache around the vegetable garden

Wisconsin says anise hyssop is popular with bees, especially bumblebees, and with butterflies and hummingbirds, though it notes the Korean mint selection 'Golden Jubilee' draws fewer pollinators. NC State says the flowers last most of the summer, and anise hyssop blooms from late July into fall (NC State), so a clump at the end of a bed keeps pollinators around the vegetables late in the season (our reading). See flowers that attract beneficial insects. Wisconsin suggests pairing it with bee balm, coneflowers, Russian sage and goldenrod.

Frequently asked questions

When is the best time to plant agastache?

In spring after the last frost (Almanac), or in early fall so roots establish before winter. Ask Extension warns that late fall planting risks frost heaving.

How do I grow agastache from seed?

The seed needs light and benefits from cold, moist stratification (Wisconsin). Sow outdoors in fall once the ground freezes, or chill seed about 30 days in a damp paper towel and start it indoors 6 to 8 weeks before the last frost (Almanac). Barely cover it.

Why did my agastache die over winter?

Usually wet soil. NC State says wet winter feet kill agastache and that several kinds will not survive winter in wet, heavy soil. Plant in a raised bed, a container or fast-draining ground.

Is agastache a perennial?

Yes, but often short-lived (Wisconsin). Hardiness varies by species, from about Zone 3 or 4 for anise hyssop to Zone 6 for 'Black Adder' (Wisconsin, NC State).

Should I fertilize agastache?

Very little. The Almanac says rich soil or extra fertilizer gives fewer flowers and floppy stems, and uses only a thin layer of compost every year or two.

Does agastache spread?

Anise hyssop self-sows readily, though Wisconsin says seedlings are easy to pull. Sterile hybrids such as 'Blue Fortune' do not set seed and are grown from cuttings.