There is absolutely no doubt in my mind that one of the most powerful plants we can include in the landscape to support a nearly unimaginable amount of pollinators are the mints we collectively know as mountain mints (Pycnanthemum). I have never witnessed more diversity or density of wasps, bees, and other Hymenoptera species on any other plant than I have with Pycnanthemum.
Pycnanthemum muticum
Unfortunately, many of us that like tidy, non-spreading plants are completely put off by the super-aggressive spreading nature of the most widely known species, Short-toothed Mountain Mint (Pycnanthemum muticum). While there is a place for plants like this, few of us have acres of moist meadow that can be sacrificed to make room for this plant in our gardens. Luckily for those of us who have smaller gardens and yearn to make a difference by adding a positive impact to our local biodiversity there are many, many wonderful species that add beauty, structure and importantly stay put! I felt the need to provide a resource to a vast majority of the species and cultivars that provides you the knowledge to know which are right for you and which are nice to visit on the roadside in the wild.
The name “mountain mint” is a bit misleading as many of the species are found nowhere near a mountain, nor even anything that could reasonably be called a hill. Many of the best species for cultivation come from the flatlands but there is apparently no room for flatlanders in the common names chosen by “experts.”
Non-aggressive, Clumping Mountain Mints
Pycnanthemum albescens ‘Malcolm Vidrine’ – Malcolm Vidrine Whiteleaf Mountain Mint
This rates at the top of our list of wonderful garden plants because of its tightly clumping habit, its attractiveness to pollinators and, above all else, the incredible fragrance! This species reaches 3’ in height with abundant branching above with stems produced in very close proximity and thus supporting each other and holding the plants rather erect even late in the season. Ours have formed patches 3’ x 3’ in four years. The odor is intense when brushed or bruised, even brushing against the plant in passing can best be described as smelling for all the world like a pack of Wrigley’s Doublemint ® gum! This plant lands on the top of my list of absolute best fragrance plants. Not all Pycnanthemum albescens have this distinctive odor, most have an odor that is frequently described as camphor-like. Malcolm Vidrine, a professor at Louisiana State University, Eunice, discovered and introduced this amazingly minty-fragrance variety from populations in southwest Louisiana. The species ranges mostly west of the Mississippi River, from southern Illinois and Missouri south to east Texas and extending east, mostly in the Gulf Coastal Plain to Florida and Georgia – nowhere near the mountains! (Hardiness Zone 5a-9b, at least)
Pycnanthemum beadlei in the garden
Pycnanthemum beadlei - Beadle’s Mountain Mint
Beadle’s Mountain Mint is a very tall species, not as branched as Whiteleaf Mountain Mint and has a more typical strong minty fragrance. This species is very attractive to pollinators and can reach 4’ in height. If you’re looking for a clumping species to fill a gap and provide pollinator support, this could be a plant for you. It is native to thin soils near granitic outcrops in the southern Appalachians but is not found colonizing road banks and forest margins like the similar P. incanum and P. pycnanthemoides. The easiest way to determine if you’ve got a P. beadlei or one of its look-alikes is to see if the middle stem leaves are short fuzzy on the underside or smooth, if they are smooth then likely you have P. beadlei. (Hardiness Zone 5a-8b, at least)
A dense, blooming mat of Pycnanthemum flexuosum
Pycnanthemum flexuosum ‘Voices’ – Savanna Mountain Mint
Savanna Mountain Mint has by far the best form for the garden. The 1-2’ tall densely branching stems are held stiffly erect and don’t flop at all. They are crowned with a mass of attractive whitish-to-light lavender flowers held in grayish-green bristly clusters. This plant would be perfect in all regards if it had more odor. The lack of a strong minty scent doesn’t detract hordes of pollinators from visiting or gardeners from including it in their designs. This one is tied with ‘Malcolm Vidrine’ for the prize of most garden-worthy mountain mints. This species is found in moist (mesic) longleaf pine flatwoods and savannas throughout the coastal plain from Virginia south to Florida and west to Alabama and adapts amazingly well to virtually any garden soil. (Hardiness Zone 5a-9b)
Pycnanthemum incanum 'Stowe Away'
Pycnanthemum incanum – Hoary Mountain Mint
Hoary Mountain Mint is a widespread species found mostly in the northern half of the eastern United States where it may be encountered growing in forest margins. This species forms tight clumps and can reach a height of 3-3.5’ with ample branching above to form a beautiful bushy crown. The brilliant fuzzy, whitish (hoary) upper leaves that subtend the inflorescence create a long-lasting and dramatic contrast to the darker green stem leaves and provide for long-lasting interest in the garden. The plant generally has a pleasing light minty mixed with camphor odor. Pycnanthemum incanum is extremely easy to grow in virtually any soil from moist to dry if it receives partial or full sun, though the plant is best developed and bush in full sun. (Hardiness Zone 5a-8b)
Pycnanthemum pycnanthemoides in bloom
Pycnanthemum pycnanthemoides – Southern Mountain Mint
Southern Mountain Mint is the dixie cousin of Hoary Mountain Mint and is similar in most regards. It is distinguished by minute details of the calyx (the green parts of the flower below the colorful petals). The calyx lobes in Southern Mountain Mint are narrowly triangular with long narrow tips compared to the more triangular calyces in Hoary Mountain Mint. Southern Mountain Mint occupies similar habitat but is prevalent in the southern half of the eastern United States. It is easy to grow in virtually any soil in partial or full sun and is very tolerant of our steamy summers and warm nights. The odor of the foliage can vary considerably with some forms having the scent of mint and camphor and others with a strong rose-like odor that is reminiscent of room deodorants! (Hardiness Zone 5a-8b)
Pycnanthemum tenuifolium 'Campbell Carpet' in bloom
Fantastic Groundcovers
Pycnanthemum tenuifolium ‘Campbell Carpet’ – Campbell Carpet Narrowleaf Mountain Mint
While typical Pycnanthemum tenuifolium reaches 30-36" tall, the foliage of Pycnanthemum 'Campbell Carpet' tops out at a mere 8" tall, making a superb groundcover of soft-textured, slightly minty fragranced foliage. It forms a clump 7' wide in a mere 3 years. The 18" tall pollinator-attracting flowering stems top the clump with clusters of lavender-white flowers, starting in early summer and followed by attractive smoky purple seed heads. If you've got sunny ground to cover with average to dry soils, Pycnanthemum 'Campbell Carpet' is for you. (Hardiness Zone 6a-8b)
Ladies and Gentlemen, We Have a Runner
Pycnanthemum muticum – Short-haired Mountain Mint
Pycnanthemum muticum attracting a pollinator
As much as I want to hate this plant for its nasty habit of running at the speed of an Olympic sprinter, I simply can’t. If you have a meadow where it can naturalize or a whole lot of space to spare, this species will make a rapidly expanding dense cover of 1.5-2’ tall stems with very pale whitish upper leaves and an extremely pungent odor of Pennyroyal. The leaves do contain Pennyroyal Oil, which can cause complications with pregnancy and although small amounts may taste wonderful, be very careful consuming much of this because this chemical can cause all sorts of complications. There are two forms of this plant, one that may represent an undescribed variety or perhaps novel species is found in mountain bogs in the Blue Ridge Mountains. The strong scent of Pennyroyal reminds me of being a kid wandering through the bogs of Alleghany County. No matter the form you are growing, few plants are more attractive to pollinators, especially a myriad of fascinating wasps species. (Hardiness Zone 5a-8b)