Monday, July 22, 2019

Mountain Mints

Mountain mints are members of the genus Pycnanthemum.  This translates from Greek as dense flower, an appropriate name for these pollinator favorites.  There are 19 species of mountain mints, all native to North America, found primarily the eastern half of the continent.  These plants have tight clusters of small white to purple tubular flowers that are very attractive to pollinating insects.  Many of these species have pleasantly mint-scented foliage.  The leaves can be used to make a mint flavored tea, although one species, short-toothed mountain mint, contains higher levels of a toxic terpenoid, pulegone, than the others.  They are also resistant to deer browsing, at least in part due to these terpenoid compounds.

This hoary mountain mint was growing along
a trail near the Potomac River.
Over the past couple of years I have added three species of mountain mints native to the Mid-Atlantic region.  The first one that I put in was hoary mountain mint, P. incanum.  (Incanum means gray.)  Its native habitat is listed as upland woods, which I interpreted as dappled shade with average moisture soil (mesic).  I have observed this species growing happily along some nearby trails.  

At home I planted it in a woodland edge, but it failed after about a year, probably due to too much shade and competition.    Where it has been successful is in open shade with dryish soil and less competition.  I expect it would be happier with a little more moisture and a little less shade. 

Note the grayish blush on the leaves and stems.  Also,
 the teeth on the leaf edge are small and widely separated.

Short-toothed mountain mint (P. muticum) is a species that I’ve had more success growing at home.  It seems happy growing in dappled shade in average well drained soils.  It needs more moisture than hoary mountain mint to excel.  Like hoary mountain mint it has a pleasant minty scent when disturbed and is very attractive to pollinators.  It is a more upright growing plant than hoary mountain mint.  On one site where I have it growing it is leaning over as it is reaching for the sun. 

Short-toothed mountain mint has white flowers and there are many short teeth along the leaf margins. 
Also the the leaves are broader in the center and thy are nearly sessile (no petiole).

The third species I have planted is slender mountain mint (P. tenuifolium).  This species, with its very narrow leaves, is well adapted for sunnier, drier locations.  Unlike the other two species discussed here, its foliage lacks a strong minty scent.  Even so I have not noticed any deer browsing on its foliage or flowers.  On the plus side it has relatively over-sized pink-tinged flowers that bloom from late spring to mid to late summer.  

The flowers of slender mountain mint come in dense clusters
making them look much larger than they are individually.

I got the slender mountain mint to plant opposite a threadleaf coreopsis (Coreopsis verticillata ‘Zagreb’) with the idea that the similar foliage would create a symmetrical design.  While the foliage of the two plants is similar, the laxer habit and bluer foliage of the mint gives a different impression than the tighter, upright form of the coreopsis.  This combination has worked out well for the pollinators. The coreopsis reach peak bloom in mid-June and the mountain mint took over in late June and is still going strong into mid-summer.

Coreopsis 'Zagreb' is on the left of the walk, slender mountain mint is on the right, behind the post. 
This combo doesn't look bad, but they are definitely different looking plants.

Overall I have been well pleased with my mountain mints: long-lasting minty foliage for me and lots of nectar-rich flowers for the pollinators.