Paperbark Maple in UT Gardens, Knoxville, photo by Andrew Pulte

Paperbark maple is a star in the winter landscape in the University of Tennessee Gardens, Knoxville. The tree's mature stems exfoliate thin sheets of cinnamon-brown adding interest to its overall appearance. Photo by A. Pulte, courtesy UTIA.  Download image.



UT Gardens December 2014 Plant of the Month:
Paperbark Maple

Submitted by Andrew Pulte, University of Tennessee Department of Plant Sciences

If you were to ask me what the most photographed plant is during the winter at the UT Gardens, Knoxville, without pause I would tell you it is either of the two paperbark maple specimens in residence.  Visitors seem to be drawn to their mature stems that exfoliate thin sheets of cinnamon-brown.  Under the exfoliating bark, stems have the appearance of having been polished smooth. By no stretch, the trees’ bark is the star.  Old trunks lose some of their magic with age, but young stems and new growth will continue to shine.

Paperbark maple (Acer griseum) is an iconic Chinese species that is well suited for use in small yards. As plants go, this one has not been stateside for very long. In the fall of 1907, an early plant explorer from the Arnold Arboretum, Ernest Henry Wilson, collected at least two seedlings of Acer griseum in Hubei Province, China. These two seedlings were added to the collection at the Arnold Arboretum in December that same year. 

Maples in general have very complex flowers, and their intricacies are fascinating.  A study of paperbark maple flowers opens an important window into understanding how this plant lagged into popular commerce.

The tree’s flowers are solitary, greenish yellow and appear inconspicuously as the leaves unfurl in the spring.  Technically, the species is “androdioecious.”  That means some individual plants have only male or staminate flowers, and some individual plants have “perfect” flowers with both male and female parts. Male trees produce no seeds and plants with “perfect” flowers often have seed that is not viable.  I have collected and planted hundreds of seeds in my lifetime and have never germinated one.  There is some variation from plant to plant, but this plant that is hard to grow from seed.


Additionally, propagation from cuttings is difficult.  Brotzman’s Nursery reported in the early 1980s that they had planted between 2,000 and 3,000 cuttings using a variety of methods and only one had taken root. 
Imagine Wilson’s trip to central China in 1907 where he had the good fortune to collect the first two plants in a mountainous region of rural Central China.  He may not have known about the botany of this maples flower, but if he were to bring back only male plants, or if they didn’t survived the journey - that would most likely be “it” until someone ventured back to Central China.

Luckily, for Wilson and gardeners everywhere, he brought back one male tree and one tree with perfect flowers. Both trees are still alive and can be seen on the grounds of the Arnold Arboretum in the historic neighborhood of Jamaica Plain in Boston, Mass.  The specimen with the “perfect” flowers regularly produces some viable seed and is undoubtedly the source of the first generation of paperbark maples planted in North America.  The Arnold Arboretum first distributed seeds and seedlings in 1927, twenty years after Wilson brought them home.

W
ith the wide range of climactic conditions throughout the state of Tennessee, some gardeners have found success with paperbark maple and others have not.  I have seen several nice specimens in all regions of the state.  However, I have also talked to gardens in all three regions of the state that have not found success. Overall, I would say the warmer temperatures throughout Tennessee are not the ideal growing condition for this tree. That being said, when they find a good home, paperbark maples really look nice and could be worth a shot. Planting in afternoon shade with evenly moist, well-drained soil will give trees the best chance of survival.

Trees will most likely top out at between 20 feet and 30 feet in height, with a more conservative spread.  The more shade they are given, the more upright they tend to grow. Overall paperbark maples are slow growers and have relatively clean foliage that can have a nice orange-red look in the fall.  The leaf shape is not the iconic typical maple –each leaf is comprised of three leaflets (trifoliate).

Paperbark maple is a true specimen tree and once established has the potential to be the star of any garden.  Even though the beautiful bark is the tree’s most notable characteristic, its relatively small stature, handsome foliage and overall form make it noteworthy.  December is one of the best months to plant trees in Tennessee and the Mid-South, and paperbark maple is worthy of your consideration.


Andrew Pulte is a public horticulture specialist in the University of Tennessee Department of Plant Sciences. He works closely with the staff of the UT Gardens. The gardens includes plant collections located in Knoxville, Jackson and Crossville. Designated as the official botanical garden for the State of Tennessee, the collections are part of the UT Institute of Agriculture. The gardens’ mission is to foster appreciation, education and stewardship of plants through garden displays, educational programs and research trials. The gardens are open during all seasons and free to the public. For more information see the Gardens website:
http://utgardens.tennessee.edu.


###

Contact:

Andrew Pulte, UT Department of Plant Sciences,
pulte@utk.edu