Mountain Mint

As the new shoots push up in spring, drive a spade straight down through the soil in a circle at the edge of the clump you want to keep, then pull up the shoots outside that line by hand. The rhizome pieces you lift come up with shoots attached and can be replanted elsewhere or given away. Mountain mint is a vigorous grower that spreads by rhizomes in good conditions, so a clump left alone will crowd its neighbors. NC State's guidance is direct: if spreading is not wanted, prune the roots in spring with a spade. Doing it while the plant is still short does the containment and the propagation in one pass.

Leave the flowering clump unsprayed from the first open bracts to the last, and watch what shows up - this is the plant to stand next to. If something nearby genuinely needs an insecticide, spray it on a still evening and do not let the drift reach mountain mint in bloom. In a Penn State study running 2012-2015 that compared 86 species and cultivars of native pollinator plants, clustered mountain mint drew the most pollinator visits and the most diverse mix of them - bees, butterflies, wasps, syrphid and tachinid flies. It rarely warrants a spray in any case: NC State reports no serious insect or disease problems on this plant.

Keep the soil somewhat moist through the first growing season while the roots take hold. After that, water only in a real drought, and deliver it at the soil line rather than over the foliage. Mountain mint is very drought tolerant once established, and keeping the soil on the dry side afterward is also the gentlest brake there is on how fast the colony spreads.

When the top bracts start to silver over and the buds have swelled but not opened, cut stems for tea, taking only part of the clump and leaving the rest to flower. Hang the cuttings upside down in a shady spot until brittle, or dry them flat on a screen in the shade, then store the leaves in an airtight jar. Utah State's mint guidance notes that if the plant is allowed to bloom, leaf oil content decreases and the leaves are less flavorful, so the same leaf is noticeably weaker a couple of weeks later. NC State confirms the leaves and flowers of mountain mint may be used for tea. (Oil-timing guidance is drawn from culinary mint, a same-family relative, not from a Pycnanthemum-specific trial.)