Mountain Mint – Truly, a Gardeners Mint

Mint is a plant that conjures up a multitude of thoughts and emotions among gardeners. Typically, our first thought is of a plant with wonderfully fragrant foliage that happens to combine well with Ice Tea and Mint Juleps! Unfortunately, this is matched with an equally unsettling vision of a plant that knows no boundaries and will rapidly spread throughout your garden! True mints are found within the genus Mentha, and their aggressively spreading nature makes them problematic in an ornamental garden. However, there are other plants in the mint family or Lamiaceae that display a far greater degree of garden refinement and manners. Mountain Mint, botanically known as Pycnanthemum muticum, is one such member of the Lamiaceae and it defies my imagination as to why this plant is not more popular among gardeners.

Mountain Mint is certainly not a new plant to the world of horticulture. It was first discovered by the French botanist Andre Michaux (1746-1802) in 1790, when he found masses of the plant growing in Pennsylvania! Michaux initially named and described the plant as Brachystemum muticum, which was published posthumously in 1803 in his work Flora Boreali-Americana. Interestingly, in the same book he described a new genus named Pycnanthemum! Both names are from the Greek to describe the flower structure; Brachys means short and Stelma means column while Pyknos means dense and Anthos means flower. It only took a few years for the French botanist and mycologist Christiaan Hendrik Persoon (1761-1836) to assign the proper genus name in 1806. The species epithet comes from the Latin Muticus for blunt, perhaps a reference to the dome-shaped or blunt appearance of the apical flowers. Although the common name is Mountain Mint, it actually does not grow in alpine regions, but rather in open, moist fields and forest edges, which can be located along the lower elevations of a mountain.

Personally, I was not introduced to this plant until 2010 while touring Central Park. It appeared periodically throughout the park as a 2-3’ tall mass of shimmering silver along the edge of woodlands and ponds. Although the day was cloudy and it was mostly growing beneath a canopy of tall trees, the plant gave the impression of sunlight cutting through openings in the branches and illuminating the forest floor beneath. The gentleman leading the tour mentioned how these masses of Mountain Mint had been installed in an effort to reduce weeds. Naturally, I thought it was another invasive mint and was about to dismiss the plant when he noted it was merely a dense, ‘weed-suppressing’ plant and not invasive. A weed suppressing, non-invasive mint – my interest in this plant began to grow!

The shimmering, silvery effect of the plant was not the result of a true flower petal, but rather a pair of silver colored bracts or modified leaves that subtend the terminal boss of small white to light pink flowers, as seen in the image above. Much like Poinsettias and our native Flowering Dogwood, the actual flowers are very small and the primary impact is created by these bracts. For Pycnanthemum, they provide a beautiful ornamental effect for over 3 months! The flowers themselves are roughly ⅛” long, white with pink markings and are densely arranged in a ½” diameter compressed flower structure called a cyme. It is this dense arrangement of flowers that sparked the crafting of the two initial genus names. The flowers open over a 3 month period beginning in June and are a great source of nectar for bees, beneficial wasps, moths and butterflies! In fact, it is rare that the plants are not a flurry of activity when in bloom. Come winter, the clusters of dried seed capsules atop the stems have a nice winter presence, especially with a heavy December frost as pictured at the end. My interest in this plant grew even further!

The lance-shaped, dark green foliage, measures 2-2 ½ inches long and is much like a typical mint, the foliage is very aromatic when rubbed. Tightly clad to the square stems by only a short petiole, the foliage contains pulegone, an oil with an aroma reminiscent of spearmint that is very effective at repelling mosquitoes when rubbed on the skin. This aroma is also effective at eliminating deer browse!

Mountain Mint is a great plant for working into the Garden. It looks great paired with the silver foliage of Lamb’s Ear (Stachys lanata) and it is great at brightening the darker foliage of deep purple leaved plants like Purple Leaved Smoketree (such as Cotinus coggygria ‘Velvet Cloak’). I have found that the plants and stems have a very vertical appearance that can make a design look awkward when planted along the edge of a planting (as pictured at left) since the transition to the ground plane is very abrupt. It is best to have a lower growing plant or a mounding plant placed at the front of Mountain Mint to provide a more gentle transition to turf, a walkway or simply the ground plain. Plants grow well in full sun as well as light shade, providing that the soil does not become excessively dry for prolonged periods. The plants are adaptable to various soil types and pH; they are typically found growing on alkaline soils in the wild, but are tolerant of acidic soils and are surprisingly tolerant of moister soils along pond edges. The soils simply cannot remain waterlogged with ponding water for extended periods of time. The rhizomes do spread about 4-6” per year, but they are easily cut with a garden spade and the shallow stems are easily extracted, even if they have started to grow into a neighboring plant. This is a practice that should typically be done every other year.

If more of a clump forming species is of interest consider Pycnanthemum flexuosum or Appalachian Mint. Originally named Origanum flexuosum in 1788 by the American botanist Thomas Walter (1740-1789), its name was altered a century later in 1888 by Nathaniel Lord Britton (1859-1934). Britton was the American botanist who went on to cofound the New York Botanical Garden! The species epithet means pliant and is probably a reference to the flexible stems. Growing 2-3’ tall and roughly as wide, the dense root system is great for soil stabilization and since the foliage is also aromatic, it too is resistant to deer browse. The flower clusters or cymes lack the silvery bracts of its cousin, but they are much larger, typically around 1 ½” in diameter (as pictured at right). The purple flecked, white flowers remain rather diminutive, with the ¼” long tubular flowers appearing for nearly 2 months throughout the summer. Like its cousin, they are also exceptionally attractive to pollinators. Unlike its cousin, each flower has a more pronounced calyx or leafy base that initially serves to protect the flower bud and then physically support the tubular flower. Once the flower fades and drops away, each of the 5 off-white sepals that compose the calyx have a long bristly spur at the tip, giving the flower head a Sputnik or fuzzy appearance. The ultimate effect produces a bit more drama to the flower and the Garden, which I found very ornamental! This species has similar cultural requirements as its cousin and both are hardy throughout NJ, easily enduring a zone 5 winter and the summer’s heat.

Interestingly, both species began their affiliation with horticulture under different and distantly related genera within the mint family, only to find out they were in fact closely related cousins. My interest and admiration for what these plants can provide for the Garden only continues to grow as I continue to find new ways to incorporate these plants in designs! Granted, no plant is perfect, since neither of these Mints should be eaten or used as a garnish in a glass of Ice Tea or a Mint Julep! However, if you have been searching for a deer resistant native plant that is friendly to pollinators, suppresses weeds and works well others, here are 2 mints that you surely want to add to your list of great garden worthy plants!

Bruce Crawford
State Program Leader in Home and Public Horticulture, NJAES

One of the positive developments from the pandemic is the renewed interest in gardening and in particular, growing food. I have always been astonished at how many children do not know how their food is produced, other than it magically appears on grocery store shelves. Obviously, their parents did not share a passion for growing food and hopefully, that will continue to improve once the pandemic is behind us. Some fruits are not only tasty and nutritious, but have an attractive ornamental appeal. For years I have been touting the beauty and benefits of Pawpaw Trees, botanically called Asimina triloba. Perhaps now, this tree’s time has finally arrived!

Pawpaw is a member of the Annonaceae or Custard Apple Family, containing upwards of 108 different genera and 2,400 species that are principally located in tropical and subtropical regions of the world. Asimina triloba is one of 12 species, all native to North America and is the most Northern and cold hardy species of the family, distributed from Georgia north to Ontario and west to Arkansas and Missouri. It typically appears in moist, well-drained areas along shaded streams, forested lowlands and wooded slopes. Pawpaw was initially named Annona triloba in 1753 by the Swedish Botanist Carl Linnaeus (1707-1778). The genus is still in existence with around 166 species and was derived from the Taíno word Anón for fruit. Taíno was the name of the culture of indigenous people in the Caribbean prior to the arrival of the Spanish. The genus name of Asimina was penned by the French Botanist and Naturalist Michel Adamson (1727-1806) in 1763. The word was adopted from Assimin or Rassimin, as the tree was so named by the Native American Algonquian Indians. It was not until 1817 that the French Botanist Michel Felix Dunal (1780-1856) properly described the tree as Asimina triloba, although the tree continued to undergo various renditions until 1886 when it was conclusively decided by the American Botanist, Asa Gray (1810-1888) that Dunal was correct. The species epithet means 3 lobes and describes the double whorl of 3 petals that comprise the flower (see images below). The common name of Pawpaw is believed to have come from the Spanish Papaya due to the similarity of the fruit shape, size and taste.

Although Pawpaw is hardy to zone 5, its appearance certainly reflects the tropical and subtropical regions inhabited by the remainder of the Custard Apple Family. The oblong foliage is 6-12” long with a pronounced outward and gently drooping display. The leaves are arranged alternately along the stems and come autumn, develop an attractive yellow fall color in shade (picture above), although it can blend with orange when grown in full sun (pictured at left). Asimina is an understory tree, typically growing to 15-20’ in height, although heights of 30’ are not uncommon when conditions are ideal. Although it grows in shaded locations in the wild, it adapts very well to full sun in the home garden, provided it is given a little protection from the afternoon sun for the first year or so. The 1-2” diameter flowers are bell-shaped or campanulate, with the dangling flowers beginning to open along the leafless stems in mid-April. The flower buds open sequentially from the inner reaches outward, which is a great adaption in case of an unexpected late spring frost; the closed flower buds are not impacted by the chill and subsequently continue to open and ultimately bear fruit! The flowers are initially a pale green on opening as pictured above, but gradually change to a deep ‘meaty’ red at maturity. The flowers consist of an outer whorl of 3 lightly pubescent sepals or modified leaves that are also initially green before developing dark red highlights with age. The sepals and flower stem are lightly pubescent and are located at the top of the flowers once open as seen above. The six petals are arranged in two distinct tiers of three, with a larger outer whorl and a puckered inner whorl (as seen at left). The flowers have a slightly fetid odor, which in combination with the deep red color of the flower provides the clues for which creatures serve as pollinators – namely flies and beetles! Not to worry, I have never seen flies hovering around the trees and there is always good fruit set. It is important to plant several different clonal selections of Pawpaw, since the trees are not self-fertile and require at least two genetically different plants for pollination. The species exhibit what botanist call protogynous dichogamy, whereby the female stigma and the male anthers mature at different times, preventing self-pollination and inbreeding depression. My experience has been pruning the plants into a somewhat planar or two dimensional configuration, combined with removal of the root suckers helps to enhance flowering and fruiting.

Pawpaws produce the largest edible fruit in North America (pictured below), ultimately reaching lengths of 3-6” and weights upwards of 5-16 oz.! When ripe, the fruit changes from green to varying shades of light yellow, with a sweetly aromatic fragrance and a slight softness to the touch. The fruit’s taste also has tropical overtones with accents of mango and pineapple, yet with the texture of ripe banana or custard. The ripe flesh is best eaten with a spoon or made into ice cream, a smoothie or used in baking. Using a spoon is also handy since the fruits have two rows of large dark brown seeds that are challenging to eat around! The fruit has to be picked when ripe since, at least in my experience, they fail to ripen if picked too early. They also have a very short shelf life of only a few days, although the pulp can be frozen for up to a year if properly processed. Aside from sweet tasting, the fruit is also very nutritious, containing healthy amounts of Vitamin C, Magnesium, Iron, Copper and Manganese. They are also a good source of Potassium and antioxidants.

Of course, the plant did not develop these delicious fruits in conjunction with the evolution of Homo sapiens, since fossil records of Asimina date back 23 to 54 million years ago, long before the appearance of our ancestors. It is known that fruit eating Megafauna or mammals over 100 lbs. such as Mastodons, once roamed North America and were responsible for not only consuming the fruit, no doubt in one ill-mannered bite, but spreading the seed and slowly enlarging its native territory. With the loss of many of these animals between 12,000 and 13,000 years ago, the reproduction and distribution of many plants was also impacted. One rather annoying characteristic of Pawpaw is its strong tendency to sucker from the rootstock and create colonies. Although bothersome in the Garden, this trait may have allowed the plant to endure; since there was no longer a vector for seed distribution, the production of new stems allowed a colony to endure as the older trunks failed! As the Native American Indians slowly spread throughout North America, they in turn took over the task of the megafauna in spreading and planting the seed! Another trait that is both beneficial and problematic is the lack of insects or animals that eat the foliage or stems. Rarely is deer browse evident. Initially, this may sound beneficial, but like many members of the Annonaceae Family, Asimina contains acetogenins that function as a neurotoxin. These compounds are most concentrated in leaves, young stems and unripened fruit, which explains the lack of deer browse. It is also present in ripened fruits. Many cultures throughout the tropics create a tea from the leaves of plants from the Annonaceae family, which supposedly acts as a sedative. Over the course of a lifetime, this consumption creates an atypical form of Parkinson’s disease. The point being that one should not overindulge in the fruits either, but rather practice moderation!

Pawpaw is a plant that is entrenched in American culture. According to the writings of Lewis and Clark in September of 1806, Pawpaw fruits sustained their expedition for several days after their supplies dwindled and both George Washington and Thomas Jefferson were great fans and grew trees in their garden. It is certainly not without its faults. However, it is a great plant for people who are exploring fruit and vegetable gardening for the first time or well-seasoned gardeners who are interesting in exploring new food options. Without doubt, it is a delicious and ornamental tree for your garden!

Bruce Crawford
State Program Leader in Home and Public Horticulture (NJAES)

I am often accused of using descriptive adjectives more typically reserved for people when discussing plants. Terms like handsome, attractive and elegant frequently roll of my tongue, along with far less complimentary terms on occasion. On the other hand, terms like eloquent, ethereal and graceful are words I typically do not use to describe a plant. However, I do believe they are the perfect adjectives to describe the Fringe Tree, botanically named Chionanthus virginicus, especially while it is covered with its fleecy white flowers of spring.

Fringe Tree is a member of the Oleaceae or Olive Family. The genus includes nearly 150 species, almost all of which are evergreen and native to tropical regions of the world. Chionanthus virginicus is native from NJ south to Florida and West to Oklahoma and Texas. The genus name was originally penned by the Swedish Botanist Carl Linnaeus in 1753; inspired by the snowy white flowers, he crafted the genus from the Greek Chion for snow and Anthos for flower. Linnaeus also provided the species epithet and described the plant in 1753. The species name refers to the colony of Virginia, which in 1753 not only included the current state of Virginia, but also the regions now known as Kentucky, Indiana, Illinois and portions of Ohio and Western Pennsylvania.

In general, Chionanthus virginicus is slow growing, appearing naturally in moist woodlands along stream banks and in exposed rocky glades. It frequently appears as a multi-stemmed shrub, reaching 15-20 feet tall and slightly wider, as pictured at right in the Morris Arboretum. However, under perfect conditions, they can reach heights of 30 feet by equal or greater widths. Depending upon the year and location, the white flowers that inspired the name can appear in late April, although May into early June is more typical for NJ. The floral display lasts for upwards of 2 weeks and looking up into a canopy of the pendant flowers can be a very transformative moment for the gardener! The flowers emerge from buds at the base of the leaves or leaf axils and freely dangle along the stems. The flowers are arranged in panicles, which have a central stem with three-flowered clusters radiating outwards along this stem. The overall panicle ranges from 4-10 inches long and up to 6 inches wide. The plants are dioecious, with individual plants having all male or all female flowers, a trait certain species adopted to prevent self-pollination and inbreeding depression. The individual flowers consist of 4-6 strap-like lobes or petals that are up to 1 inch long on the female and slightly longer on the male flowers, by 1/16” wide (as pictured at right). The flowers are wonderfully fragrant and give the plant a very appealing lacy or fringe-like appearance that gave rise to its common name. In some regions the plant is also called Old Man’s Beard, since the dangling panicles resemble a frothy white beard! The male flowers have 2 stamens that aid in making the flowers appear showier, while the female flowers have a single central stigma. Although the male flowers may be showier, it is the female flowers that develop clusters of blue to purple fruits come September. The fruits are technically called a drupe, with each containing a single large central seed. The drupes are much beloved by birds and are a good reason for not planting a clonal mass of simply the showier male selections. The fruits are equally vital to the garden, if not more so, for their attractive display and provisions provided for wildlife (pictured below in late November).

The foliage appears with the flowers and is positioned such that it nicely compliments rather than hides the blossoms. The leaves are a dark, glossy green, measuring 4-6 inches long by 2 inches wide and transform to an attractive golden yellow come fall, especially if the plant is located in full sun (pictured below at the end of the article). The bark is a smooth gray on young stems, maturing to a ridge and furrowed or occasionally a warty appearance on older specimens.

The other commercially available and hardy species for North American gardens is Chionanthus retusus, the Chinese Fringe Tree. Native to China, Korea and Japan, it too grows as a multi-stemmed large shrub, reaching 10-20 feet tall and wide. It can also appear as a single stemmed small tree, whereby it can reach heights of 30 feet tall. Individual plants are often genetically oriented to their ultimate form, although training will have some impact on whether they assume a shrub or tree habit. Chionanthus retusus was originally brought to Europe in 1845 by the Scottish botanist and plant hunter Robert Fortune (1812-1880) with a second specimen appearing prior to 1860 from the English botanist and plant collector Charles Maries (1851-1902). The species epithet is from the Latin Retundere, meaning to pound back or blunt. A retuse leaf has a rounded apical tip with a v-shaped notch, which describes the foliage of many plants with their rounded, glossy green leaves that are up to 4 inches long and 3 inches wide. Interestingly, some plants have elliptical foliage that comes to a point. The leaves also have a thick almost leather-like texture. The plant was named and described in 1852 by two individuals: the English botanist and orchid enthusiast John Lindley (1799-1865) and the English Gardener and Architect Joseph Paxton (1803-1865). The foliage is much more frost tolerant than its North American cousin, with the foliage remaining green through a number of heavy November frosts. During most autumns in the north, the foliage drops while still green in late November, but in more southern gardens the foliage will change to a buttery yellow.

Chionanthus retusus also has dioecious flowers. The flowers differ from their North American cousin by being erect and produced from the apical buds at the tips of the branches. Although the panicles are smaller, only reaching 2-3 inches long and as wide, the petals are wider, reaching from ⅛ to nearly ¼ inch wide (as seen below). The wider petals combined with the apical positioning of the flowers provides for a more dense and brilliant floral display (pictured at left), which is attractive yet not quite as ethereal as its cousin in my opinion. The bark is showier on this species, as the younger stems are cinnamon brown in color with small waves of peeling bark running the length of the stems. Over time, the bark matures to a dark brown and gradually becomes ridge and furrowed.

If space is restricted and a more columnar form is needed, consider Chionanthus retusus ‘Tokyo Tower’ (pictured below). It slowly matures to 20’ tall by 8’ wide. The plant pictured below was planted 12 years prior to the picture being taken, when it measured a more humble 4-5’ in height! The form is decided upright and once again it yields an attractive floral display. The plant is female and produces an attractive fruit set in the fall, providing a male plant is within a pollinators reach.

Both species of Fringe Tree perform admirably in full sun or light shade and are very adaptable to a broad range of soil types and pH. I have seen large specimens of Chionanthus retusus planted near busy roadways where they are subject to significant amounts of road salt throughout the winter without any noticeable impact. The American Fringe tree is hardy to zone 3 and while the Chinese Fringe Tree is only hardy to zone 5, they are both suitable for NJ gardens. The one issue to consider and keep an ever watchful eye out for is Emerald Ash Borer, as both species are susceptible.

Eloquent and graceful, Chionanthus is certainly a plant that has been overlooked too long in the gardening world. It is very easy to grow and, providing you have chosen seedling diversity, you will not only have an attractive spring floral display, but a late autumn display of fruits complimented by our foraging winged friends. What more could a gardener ask?

Bruce Crawford
Program Leader in Home and Public Horticulture