Pycnanthemum flexuosum - Mountain Mint

The Pycnanthemum flexuosum is a highly aromatic American perennial that bears tightly packed white flowers at the top of tall upright stems in summer. Its mint-scented foliage turns beautiful shades of red in autumn. The plant prefers cool to moist, sandy and acidic soils, in either full sun or light shade.

The Appalachian Mint is native to the coastal plains of the United States, from Virginia to northern Florida, as well as westwards to Mississippi. It mainly grows on the edges of acidic wet meadows called pocosins, and peaty marshes, alongside pines, bald cypresses, and oaks. It belongs to the Lamiaceae family, which includes many ornamental plants loved by gardeners. In particular, its common name reminds us that it is a close relative of mints. Like them, Pycnanthemum's foliage (reminiscent of oregano) is aromatic, emitting a powerful and pleasant minty fragrance. Between June and September, depending on the conditions, it produces small white flowers (or very pale purple) at the tips of its tall quadrangular stems, forming dense heads called glomerules. These flowers are highly attractive to pollinators! Moreover, the elongated teeth of the calyx give the whole plant the appearance of a small silver hedgehog, adding to its decorative value. Under optimal conditions, the plant will reach a height of 60 to 90 cm (24 to 35in) with a diameter of 50 cm (20in). It spreads through short suckers, but much slower than its mint relatives. As temperatures cool in autumn, the deciduous foliage takes on beautiful reddish hues, further extending the plant's period of interest. The stems persist during part of the winter, and can be cut back to ground level before regrowth begins.

Due to its origins, Pycnanthemum flexuosum thrives in cool, even moist, but well-drained soils. It is quite hardy and prefers a sandy, neutral to acidic substrate in an open and warm location. Sun or light shade is therefore preferred. It is worth noting that, in its natural habitat, the plant is frequently subjected to brush fires. On the other hand, it tolerates long dry periods during the summer, as well as winter waterlogging. Given its strong fragrance, very few herbivores enjoy consuming its leaves.

To recreate a fresh and well-drained "American meadow" bed, it is a perfect match with plants such as Rudbeckia subtomentosa, Rudbeckia maxima, Monardes, or even Liatris spicata. Some grasses like Molinies, Andropogon gerardii, or Schizachyrium will bring a welcome lightness to the ensemble.