Specimen Spotlight: Mountain Mints

by Melinda Heigel, EMGV

Mountain Mint still putting on a show in September.
(Image credit: Melinda Heigel)

Merely mentioning the word mint to gardeners may send them running in the opposite direction for fear of being overtaken right where they stand by this pungent, intoxicating herb. While plants in the Mentha genus such as spearmint (Mentha spicata) and peppermint (Mentha x piperita) may invoke pleasant memories of chewing leaves on lazy afternoons in your grandmother’s garden and definitely have an honored place in the culinary world, their invasive growth habits can show little respect for boundaries and quickly become problematic in the garden.

Well…how about mountain mints? I really only became aware of these plants within the last few years. With the interest in pollinator-friendly gardening on the rise, I began hearing horticultural experts sing mountain mints’ (Pycnanthemum spp.) praises as one of their top picks for the landscape.

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Characteristics

A host of pollinators including butterflies and moths are drawn to the plant’s enticing nectar.
(Image Credit: Judy Gallagher CC BY 4.0)

Mountain mints are native to the Eastern US and grow in all areas of North Carolina. In their naturally occurring habitats, you’ll often find them growing in moist open fields, at the edges of forests, and in lower elevations despite the alpine-sounding name. Both culinary mints we know and mountain mints are in the same scientific family (Lamiaceae), but they are different genera —Mentha and Pycnanthemum, respectively. However, both share a minty or thyme-like fragrance when crushed. Aside from smelling great, these plants have a lot going for them. Mountain mints are known for their rabbit and deer-resistant properties. Mountain mints are also super pollinator attractors, with their nectar drawing a host of beneficial insects. From June until September, look for scores of native bees, honey bees, wasps, moths, and butterflies buzzing around this plant. In a 2013 Penn State Extension study testing 86 native species and cultivars, clustered mountain mint attracted the most diverse group of pollinators of all the plants tested. (1)

Most mountain mints have bracts much like our beloved North Carolina state flower the Dogwood blossom (Cornus florida), some silver in appearance. The plant’s small flowers range from white to light pink to lavender in the compact center of the plant (called a cyme) and give a subtle ornamental effect. A few as outlined below can offer more showy flowers. These perennial and deciduous plants have a mounding upright habit and generally reach a mature size of 3 feet tall by 3 feet wide. And let me tell you, this plant is versatile. Mountain mint is excellent for naturalizing a larger area, in a cottage garden, for native plant gardens, or even mixed in a perennial border or bed. And while it flowers best in full sun, it can also grow in part sun to part shade. It’s typically not picky about soil either; it only wants good drainage. Its dense growing habit means it can serve as a great weed suppressor. Mountain mints can be grown by either seeds or plant division. While not as invasive as true mints, it can spread out over time at a typical rate of 4-6 inches annually. Keeping it in check is fairly easy, though. If the plant gets too big, dividing or simply severing part of the plant’s rhizome root system with a spade is enough to rein it in each year.

Detail of silvery bracts surrounding compact clusters known as cymes with delicate lavender flowers. (Image Credit: Cathy Dewitt CC BY 4.0)

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Types of Mountain Mint

While there are over 20 species of Pycnanthemum and many can be found in North Carolina, here are a few examples to whet your appetite for this pollinator-friendly plant. The following mountain mints can often be found for sale these days at local nurseries, especially those that have a focus on native plants.

Narrow-leafed Mountain Mint (P. tenuifolium) and close up of its flowers. The North Carolina Botanical Garden crowned this species its 2019 Wildflower of the Year. The needle-like leaves lend great texture and the clustered white flowers are a stand-out addition to the garden. (Image Credits: (Left) Cyndy Sims Parr CC-BY-SA 2.0; (Right) Dan Mullen CC BY-NC-ND 2.0)

Hoary Mountain Mint (P. incanum) leaves, bracts, and flowers. This species gets its name from short white hairs that cover its stems. It has a lovely silver appearance that makes you think the plant could have been lightly dusted with snow or powdered sugar on both leaves and bracts. The wider leaves are a good identification guide. (Image Credits: (Left) S.B. Johnny CC BY-SA 3.0); (Right) Tom Potterfield CC BY-NC-SA 2.0)

Appalachian Mountain Mint (P. flexuosum) with its impressive architectural blooms and the distinct leaves. This type of mountain mint is found most frequently in the Piedmont to the coast in North Carolina. It sports more flowers than other Pycnanthemum species that are white to lavender in color and can be used for cut flowers. These impressive blooms turn into lovely dried seed heads if left to overwinter in the garden. This species is a larval host plant for the Gray Hairstreak Butterfly (Strymon melinus) and supports the wavy-lined Emerald moth (Synchlora aerata). (Image Credits: (Left) Debbie Roos; (Right) Leaves, Nate Hartley CC BY-NC 4.0).

Blunt Mountain Mint (P. muticum) is also known as short-toothed mountain mint. This species is often less drought tolerant than other Pycnanthemum and prefers moist to medium well-drained soils. It also supports wavy-lined Emerald moth larva, and its native habitat is often woodland areas and thickets. Its dark green leaves can also appear sugar-coated when planted en masse. (Image Credits: (Right) Fritz Flohr Reynolds CC BY-SA 4.0; (Left) Flower and Bee (Wake County, NC)Cathy Dewitt CC BY 4.0)

Make room in your garden for mountain mints! They are plants worth discovering.

Notes

(1) Ellis, K. 2013. Identifying and Promoting Pollinator-Rewarding Herbaceous Perennial Plant Species. Final Report to Pennsylvania Department of Agriculture. 16pp.

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Additional Resources and Information

North Carolina Botanical Garden’s 2019 Wildflower of the Year: Narrow Leaf Mountain Mint (Pycnanthemum tenufolium)

https://ncbg.unc.edu/2019/05/30/2019-wildflower-of-the-year-narrow-leaf-mountain-mint/

Rutgers University’s New Jersey Agricultural Experiment Station

https://njaes.rutgers.edu/plant-of-the-month/pycnanthemum.php

NCSU’s Plant Toolbox site on Mountain Mints and excellent video starring the Narrow Leaf Mountain Mint

https://plants.ces.ncsu.edu/plants/pycnanthemum/

https://plants.ces.ncsu.edu/plants/pycnanthemum/

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