Plant Fact Sheet
PURPLE GIANT
HYSSOP
Agastache scrophulariifolia
(Willd.) Kuntze
Plant Symbol = AGSC
Contributed by: USDA NRCS Cape May Plant Materials
Center
USDA-NRCS PLANTS Database / William S. Justice @ USDA-NRCS
PLANTS Database
Alternative Names
Common Alternate Names:
giant hyssop
prairie hyssop
Scientific Alternate Names:
Hyssopus scrophulariifolia Willd.
Agastache scrophulariifolia var. mollis (Fernald) A.
Heller
Uses
Wildlife Use: Purple g iant hyssop provides a nectar source
for pollinators and is well suited for use in pollinator
restoration habitat. Preliminary observation found that
purple giant hyssop attracted 14 different species of
Hymenoptera and Lepidoptera in Cape May, New Jersey.
The halictid bee (Agapostemon virescens), leaf-cutter bee
(Megachile mendica), and Megachile texana species were
most frequently observed visiting the flower. Other bees
known to frequent the flower are the European honey bee
(Apis mellifera), black and gold bumble bee (Bombus
auricomus), and Bombus pensylvanicus. The flower also
attracts goldfinches and hummingbirds.
Ornamental
Purple g iant hyssop is a popular ornamental p lant. The
relatively large height of the plant makes it a good choice
as a background against fencing.
Status
Please consult the PLANTS Web site and your State
Department of Natural Resources for this plant’s current
status (e.g., threatened or endangered species, state
noxious status, and wetland indicator values).
Description and Adaptation
Description: Purple giant hyssop is a late-flowering,
native perennial herb of the mint family. It can grow
unusually tall for a mint; up to 6 feet, with diamond-
shaped stems, aromatic foliage and flowers, and vigorous
stolons. The stems are erect and form clumps. The upper
braches may be purplish.
The densely branched inflorescence is a 1–6 in terminal,
continuous, or interrupted flower spike, o r raceme. The
plant usually has several spikes. The tops of the spikes
develop into a flower and two lateral branches develop
under the flower from a common node; giving the
inflorescence a symmetrical appearance. The flower
clusters persist throughout the winter.
The individual flowers are ¼ in long, 15-nerved tubes that
are lavender to pale p ink. The upper lip has 2 lobes and
projects forward; and the lower lip curves downwards
with 3 lobes. The individual lobes are 3-nerved.
Not all flowers open at the same time. The flowers
contain 4 stamens that extend beyond the flower. The two
lower stamens curve upwards, while the two upper
stamens curve downwards. The pollen sacs are nearly
parallel.
A. scrophulariifolia is similar to blue g iant hyssop (A.
foeniculum), however purple giant hyssop has a cup-like
whorl o f green sepals (modified leaf-like bracts under the
flower) while A. foeniculum has blue-violet sepals. Often
the sepals of giant purple hyssop have colored marg ins.
Nutlets are .05-.07 in (1.5–2 mm), dark brown, rounded,
and minutely hairy at the squared-off tip.
The stalked leaves of purple giant hyssop are positioned
opposite on either side of the stem. The sharp-pointed
leaves are 4 in long and 2 in wide, with a cordate,
somewhat heart-shaped or rounded base. The margins of
the leaves are coarsely toothed and short hairs cover the
leaf stems. The undersides of the leaves are green, and
smooth or appear shaggy. Conversely, the underside of
the blue giant hyssop (A. foeniculum) is whitish. The
species name is derived from the Scrophulariaceae or
figwort family, for the resemblance of the leaves to the
figwort. When crushed, the leaves emit a distinct, anise-
like odor.
Purple giant hyssop distribution from USDA-NRCS PLANTS Database.
Adaptation: Like many members of the mint family,
purple giant hyssop grows best in moist soil or wet
conditions. It is found in rich woodland sites with dappled
shade, woodland borders, meadows, thickets, the upper
limits of floodplains, and upland woods. It prefers
recently disturbed, sandier soils where competit ion is
limited. Plants will not persist under hot and dry
conditions (USDA zone 9 or higher). Threats to its habitat
include changes in land use, competition from non-native
species, and natural succession. For updated distribution,
please consult the Plant Profile page for this species on
the PLANTS Web site.
Es tablishment
Purple g iant hyssop requires cold stratification and
sunlight to germinate. Keep the seed for 8 weeks at 40ºF
and move to 68ºF for germinat ion. The seeds will
germinate in 30–90 days in containers with good
drainage. When planting in the fall, cold stratification is
not required. For vegetative propagation, take late spring
cuttings from the basal growth that emerges in mid-
March. These cuttings can be fertilized for quicker
establishment.
Purple g iant hyssop propagates rapidly by seed and
transplants easy into natural settings. One can use it in
dry-site seed mixes for pollinator habitat at 8% of the
mix. Sow into open ground and cover with a light layer of
mulch or sow into flats and grow to 12 in (30 cm) in
height before transplanting. There are 60,000–93,000
seeds/ounce.
Management
Because purple giant hyssop requires soil disturbance for
successful establishment, regular clearings must be
created and maintained through tree-thinning, elimination
of competing vegetation, or by delaying natural
succession cycles.
Populations of purple giant hyssop tend to be short-lived
because they are easily out-competed. Therefore, field
plots may need to be re-established every 3–4 years for a
fuller look. To encourage more vigorous growth, cut 2–6
in from the plant.
Pests and Potential Problems
Little is known about potential pests. Anecdotal evidence
suggests it can be affected by mildew and rusts. There are
mixed findings on the plant’s susceptibility to browsing
deer.
The gradual and continued loss of farmland to either
forests or urbanization continues to threaten a species that
requires open fields and meadows for habitat.
Environmental Concerns
None
Prepared By
Christopher M. Sheahan; USDA-NRCS, Cape May Plant
Materials Center, Cape May, New Jersey.
Citation
Sheahan, C.M. 2012. Fact sheet for purple g iant hyssop
(Agastache scrophulariifolia). USDA-Natural Resources
Conservation Service, Cape May Plant Materials Center.
Cape May, NJ. 08210.
Published 07/2012
Ed ited:
For more information about this and other plants, please
contact your local NRCS field office or Conservation
District , and visit the
PLANTS Web site or the Plant
Materials Program Web site
materials.nrcs.usda.gov>
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Plant Fact Sheet
PURPLE GIANT
HYSSOP