Blue Giant Hyssop

Agastache foeniculum

Description & Overview

Blue Giant Hyssop is a mint family perennial native to prairies in northwest Wisconsin. When crushed, leaves give off a licorice scent which many people find so pleasant they add it to their tea. Luckily for the gardener, many deer and rodents readily avoid it for the very same reason! Rest assured, pollinators are still magnets to the showy lavender-blue flower spikes that begin blooming in June and don’t stop until September.

You may also know this plant as Anise Hyssop or Fragrant Hyssop.

Core Characteristics

Mature Height: 2-4 feet
Mature Spread: 1-3 feet
Growth Rate: Fast
Growth Form: Clumping Perennial
Light Requirements: Full Sun to Partial Shade
Site Requirements: Average to dry moisture
Flower: Purple Racemes
Bloom Period: June-September
Foliage: Green, Fragrant
Fall Color: N/A
Fruit Notes: Nutlet

Suggested Uses:

Pollinator Projects: Blue Giant Hyssop is definitely a plant with a job and is a pollinator magnet! Use it in a butterfly garden or general pollinator garden to attract all kinds of butterflies, bees, flies, and more. It also attracts hummingbirds! Plant along borders, en masse, or in the forefront of a mixed bed.

Restoration: As a native plant, Blue Giant Hyssop can be used in prairie restoration projects, native gardens, or simply to naturalize a large space as it will re-seed given time. It is at home in disturbed soils and is commonly found along roadsides.

Edible: Plant it in an herb garden and use it to flavor teas and salads.

Wildlife Value:

The color of the flowers varies from white to blue to lavender and although they are not fragrant they are irresistible to many species. Hummingbirds, butterflies, bees, and beetles prefer these flowers over many others. Long-horned bees, Bumblebees, Leafcutter Bees, Bee flies, Silver Spotted Skipper Butterfly, Peck’s Skipper Butterfly, Great Spangled Fritillary Butterfly, and more visit the flowers! Giant Blue Hyssop is an excellent choice where providing resources for pollinators is a priority.

Goldfinch, finches, sparrows, and others feed on the seeds.

Deer tend to avoid Blue Giant Hyssop due to the strong scent of the leaves.

Maintenance Tips:

This hardy, productive perennial is tolerant of many soils; however, it may develop root rot if the soil is not well-drained. In a more humid climate, it may develop leaf spot or powdery mildew. These factors can be minimized by siting the plant properly to begin with, in a well-drained location in full sun with good air circulation.

Deadheading spent flowers can extend the blooming period. Deadheading in the fall prevents seed dispersal for those who wish to slow its spread (though it is possible for it to spread by rhizomes as well).


The scent of anise from the foliage deters deer and, likely, deters some potentially problematic insects as well.

In humidity, leaves may be affected by powdery mildew or leaf spots and this may be unavoidable during a particularly humid Wisconsin summer. If the only site available is a wetter site check out this profile for Purple Giant Hyssop.

Leaf Lore:

Although the common name for Blue Giant Hyssop contains the word “hyssop,” it is not technically hyssop, nor is it related to the European plant traditionally used in herbal medicine with genus name, Hyssop.

Used medicinally as an expectorant, it is said to relieve congestion by clearing mucus from the lungs.

Aromatic leaves are used in teas and jellies or added to salads to punch up the flavor.

Giant Blue Hyssop is such a reliable pollinator plant that commercial fruit orchards use them to attract pollinators.

Companion Plants:

Complimentary perennials that also enjoy low to average moisture and full sun include Black-eyed Susan, Stiff Goldenrod, Little Bluestem, Stiff Coreopsis, Rough Blazing Star, Hairy Wild Petunia, and Compass Plant. Complementary native shrubs include New Jersey Tea and St. John’s Wort.

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