Photo © Anne Galer
By Anne Galer, Extension Master Gardener
My first encounter with mountain mints (Pycnanthemum) came when I was making the bouquets for my daughter’s wedding. We had the cherished peachy roses and hydrangeas from my garden and went in search of her two other requests: lisianthus and mountain mint. We found both at the Arlington Farmers’ Market and picked up our order at the market the day before the big event.
Mountain mint made the perfect filler for the bouquets—tiny clusters of white flowers with gray-green bracts, showing just a few shiny green leaves. So, years later when I saw a small pot of mountain mint at the Master Gardeners of Northern Virginia stall at the annual Greenspring Garden plant sale, I knew I had to have it for my garden.
Mountain mints are members of the Lamiaceae family native to the Americas. Like others in the mint family, they have square stems and a distinctive smell when crushed or brushed against. They generally grow to 3 feet in clusters spreading by rhizomes. The tiny white flowers and whitish bracts that tip the shiny-green leafed stems give the effect of a dusting of powder to the groupings in the garden.
There are over 20 species of mountain mint ranging all over the U.S. and into Canada. The U.S. Fish and Wildlife Service’s Native Plants for Wildlife Habitat and Conservation Landscaping booklet lists Pycnanthemum incanum (hoary mountain mint) and Pycnanthemum tenuifolium (narrow-leaved mountain mint) as the two species native to the Chesapeake watershed. I have Pycnanthemum muticum (short-toothed or clustered mountain mint) in my garden and find it easy to grow in full sun with most of the watering left to our normal rainfall.
Pycnanthemum incanum (hoary mountain mint) Photo © Missouri Botanical Garden 
Atteva aurea Ailanthus webworm moth on Pycnanthemum tenuifolium (narrow-leaved mountain mint) Photo © Missouri Botanical Garden
Because of its rapid growth and understated demeanor, I use mountain mint as a background plant to complement my bolder flowers. Hoary mountain mint and narrow leaved mountain mint have showier bracts and flowers making them ideal for incorporating into bouquets and arrangements.
In addition to being native to most of North America and easy to grow, they provide excellent pollinator habitat and—icing on the cake—are deer resistant. Allan Armitage’s description and recommendation in his book, Herbaceous Perennial Plants ring true: “All mountain mints can roam freely. They are better behaved in full sun and moist but not wet soils. An early haircut does wonders for their disposition: cut back in late spring. Most grow well from zones 3 to 7.”