Backyard Gardening

By Kathryn Dorman

It is a delight to see the patchwork of reds, oranges, yellows, greens, and browns in Pennsylvania’s fall forests!  Even though the Flaming Foliage Festival is over this year, you can still see a lot of “flaming foliage.”  Maple trees of many species provide a significant portion of this color palette for fall foliage in Pennsylvania.

Maple trees belong to the soapberry (Sapindaceae) family, formerly called the maple (Aceraceae) family.  According to the Nashville Tree Conservation Corps (NTCC), over 100 maple species have evolved worldwide.  There are 13 maple species which are native to North America.  This article will briefly describe most of the maple species growing in Pennsylvania.  

Every maple tree produces double-winged fruits called samaras, each with a pair of nutlet seeds.  The samaras resemble spinning helicopter blades as they fall to the ground and are blown by the wind.  Flowers bloom in spring, and deciduous leaves drop throughout fall.  Almost all maples have hand-shaped (palmately lobed) leaves, sometimes with indentations or sinuses between the lobes.  The leaves, buds, and twigs of all maple trees grow opposite each other along the branches.  The leaf color and number of lobes may vary by leaf, tree, species, and/or season (https://www.nashvilletreeconservationcorps.org/treenews/how-many-maple-tree-varieties).  

Seven maple tree species are native to Pennsylvania, and four are commercially important.  These include sugar maple (Acer saccharum), black maple (Acer nigrum), red maple (Acer rubrum), and silver maple (Acer saccharinum).  Other PA native maples include boxelder maple (Acer negundo), mountain maple (Acer spicatum) — a shrub, and striped maple (Acer pensylvanicum) — thusly named due to striping on branches and young trunks.  

According to the Massachusetts Maple Producers Association (MMPA), sugar and black maples are very similar in appearance and can also cross-breed to produce hybrids.  Some resources consider black maple to be a subspecies of sugar maple.  The leaves typically have five lobes, although black maple leaves will more often have three lobes.  Leaf margins are relatively smooth (See Photo 1).  Young sugar maple trees will have smooth gray bark, while the bark of older trees will develop deep furrows.  Samaras are horseshoe-shaped.  Both sugar and black maples can live well beyond 200 years, growing taller than 100 feet, with trunk diameters of more than 30 inches (https://www.massmaple.org/about-maple-syrup/make-maple-syrup/maple-tree-id/).  

Red maple trees get their name from the red color of their flowers, leaf stems (petioles), and fruits.  “Red maple is one of North America’s most abundant and widespread hardwood trees (MMPA).”  It can thrive in a wide variety of soil and growing conditions.  Red maple leaves often have three lobes, with many small teeth along the leaf margins (See Photo 2).  Young red maple trees will have smooth, light gray bark.  Samaras are V-shaped.  Red maple trees rarely live beyond 150 years.  Mature red maple trees can be 60 to 90 feet tall, with trunk diameters between 20 and 30 inches. 

Silver maple trees get their name from their leaves’ lighter, silvery-blue undersides.  Silver maple leaves have five lobes with deeply indented sinuses.  To me, the leaves look delicate and lacey.  The leaf margins have many small teeth.  Samaras are V-shaped.  Silver maples can live up to 150 years.  Silver maples are fast-growing trees and can reach heights above 100 feet, with trunk diameters often exceeding three feet. 

Boxelder, or ash-leaf maple, is the only species of maple tree native to North America with compound leaves.  There can be three, five, or even seven leaflets, with one leaf on the end of the stem and the others growing opposite each other in pairs.  Very young boxelder seedlings resemble poison ivy.  (I have something growing in one of my tomato pots that could be either, but I won’t test it by touching it.  I get itchy just thinking about poison ivy!)  Although it is a Pennsylvania native, boxelder can produce many seeds and get very weedy.  It is no longer recommended for planting in home gardens.  

Four non-native maple species have been introduced in Pennsylvania, with mixed results.  The Japanese red maple (A. palmatum) is not considered invasive.  We planted one beside our driveway 15 or 20 years ago, and I have yet to see any seedlings sprouting from it.  On the other hand, Amur maple (A. tataricum subsp. ginnala), Norway maple (A. platanoides), and sycamore maple (A. pseudoplatanus) are all listed by the PA Department of Conservation and Natural Resources as being invasive (https://www.dcnr.pa.gov/Conservation/WildPlants/InvasivePlants/InvasivePlantFactSheets/Pages/default.aspx).

My research indicates that the two big maples in front of our house might be a red variety of the invasive Norway maple — either “Crimson King” or “Royal Red.”  I thought they were red maples, but the large leaves have five lobes and smooth margins.  Red maples typically change color earlier in the fall than other maple species.  Our trees still had green leaves as of October 22.  If you break off a leaf stem, Norway maples are supposed to produce a bit of milky latex sap.  I didn’t see this with my maples, but it might be too late in the season.  I will have to watch for green flowers in the spring and recheck the sap.  If they are the invasive Norway maples, I will have no qualms about cutting down these trees!

As for benefits and uses, with their dense foliage, high refuge, and nutritious forage, most native maple species provide excellent habitats for birds and mammals.  Early spring maple flowers are also essential resources for local pollinators of all kinds (NTCC).  Maple trees make exceptional shade trees.  High-quality furniture is often made of maple wood.

Of course, there is the sweet business of maple syrup.  Maple syrup is mainly produced in northeastern United States and southeastern Canada.  This is the area where sugar and black maple trees are most abundant.  Since the sap of sugar and black maples has the highest sugar content, they are the most commonly tapped maple species (MMPA).  Red and silver maple trees may also be tapped for maple syrup production.  According to the United States Department of Agriculture/Natural Resources Conservation Service, even boxelder can be used to produce a form of maple syrup called “mountain molasses (https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_acne2.pdf).”

Where I grew up, four big old maple trees stood guarding our house.  They were so tall that I could barely see the leaves from the ground beneath them.  I could look closely at the leaves when I was on our raised front porch or in my second-floor bedroom.  I’m sure those trees were sugar maples, but I don’t remember my parents doing much to harvest sap from them.  Mom was an elementary school teacher, and Dad worked at Hammermill Paper Company.  Neither had the time required to make maple syrup.  Since my mother grew up on that same farm, I suspect that my grandparents did tap the maple trees at some point in the very distant past.  Considering her frugal nature and the fact that she grew up during the Great Depression, I’m pretty sure Mom’s family used everything that could be used.  These days, some people go out and tap maple trees as a hobby.  Times have certainly changed!

Kathryn Dorman has been a certified Penn State Extension Master Gardener of Clinton County since 2017.  She can be reached at clintonmg@psu.edu, or through the Clinton County Master Gardener Hotline at (570) 858-0198.