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Yellow Giant Hyssop is one of only two Agastaches native to Virginia, and the only one confirmed native to Floyd County by the Flora. The other species, Purple Giant Hyssop (Agastache scrophulariifolia), is native to several adjacent counties (Montgomery, Franklin, Patrick).
Yellow Giant Hyssop prefers rich soil in a savanna (part shade) setting, but will tolerate full sun. Along the edge of a forest clearing, or at the back of a garden, Yellow Giant Hyssop can have a nice presence without needing to be ornamental. Gardenia.net opines that “the beauty of Yellow Giant Hyssop consists primarily of its foliage of toothed, arrowhead shaped, medium to dark green leaves.” The bitter leaves are not palatable to deer or livestock. Slowly spreads to form a colony.
“The Iroquois use a compound infusion of plants as a wash for poison ivy and itch.” (Wikipedia, 2023)
This tall perennial herbaceous subshrub is not showy at all but its tiny flowers are an abundant nectar source, feeding honeybees, bumblebees, Halictid bees, and butterflies often up to the first frost. Stands tall and yellow in the fall, topped by dark brown flower spikes, and persists through the winter, unlike many perennial forbs which die to the ground, making it doubly suited to growing along the edge of a clearing or at the back of a garden where it can provide cover for overwintering insects.
Virginia Heritage Communities
Agastache nepetoides has been found in the following Virginia Heritage Community (relatively intact ecosystems that have been surveyed and catalogued by the Virginia Department of Conservation and Recreation (DCR): Inner Piedmont / Lower Blue Ridge Basic Oak – Hickory Forest [USNVC CEGL008514 Quercus rubra – Quercus montana – Carya ovalis / (Cercis canadensis) / Solidago (caesia, curtisii) Forest (G3G4/S3S4)] a type of Basic Oak – Hickory Forests. This was a single observation taken in neighboring Franklin County on the northern slope of Bald Knob just outside of Rocky Mount.
This infrequent representation in the Heritage Communities probably reflects this plant’s preference for subclimax conditions of bright part shade in relatively fertile soil, otherwise known as rich savannahs. In Southwest Virginia, these rich soil areas tend to either grow up as thick forests, too dark for Agastache nepetoides, or are cleared and kept open by agriculture and development. In past millennia, fire (both natural and human managed) and the Eastern Wood Bison would have kept some forest stands more open. Furthermore, Yellow Giant Hyssop’s C-value of 6 shows us that while it’s not so picky that we can’t grow it, it also is not so aggressive that it will withstand weeds, mowing, herbicide, and human-made disturbance. This means that the cultivated garden is the perfect place to keep it around!