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Garden Talk
"WHAT KIND OF TREE IS THAT?"
A Recap of the Members’ Tree Walk with Leaf & Limb Arborist Matthew Archibald
By Lauren Smith Hong
Annual Fund and Membership Officer
On a clear chilly morning in early February, a group of Duke Gardens members gathered together for a special treat: Matthew Archibald, an ISA Board Certified Master Arborist and educator with Leaf & Limb, a local tree service and tree care provider, led the group on a tree walk through the Blomquist Garden of Native Plants. “How do you know what tree you are looking at, especially in winter?” was the question on everyone’s mind, and Matt was the perfect person to answer.
Matt discovered his passion and purpose in life when he started learning about trees and their ever-expanding universe of information. Now a 10-year veteran arborist, he loves to pass his knowledge on to others—along with the intrigue of just how much remains unknown. Preceding the walk, Matt mentioned that tree identification and similar topics could spark a conversation that lasts for hours—depending on how interested people are, of course. Our group was indeed interested, as the 45-minute walk turned into an hour and 45 minutes of captivating content. We’re thrilled to bring you highlights from Matt’s tree walk.
TREE IDENTIFICATION IN WINTER? CHALLENGE ACCEPTED
Identifying deciduous trees in winter can be a challenge, but there are a few key things you can look for to help determine what tree you are observing.
LOOK UP!
A good first step is to look up at the canopy—is it an overstory or understory tree? This can help narrow down the list of candidates. Overstory trees like tulip poplar, oak and pine will often have a single trunk that soars to the sky in search of full sun. Many understory trees like dogwood, maple, redbud and sweet bay magnolia can have multiple trunks and/or branches, an adaptation to shadier conditions.
You can also learn a lot about the surrounding forest by observing the canopy. If the forest has been largely untouched, you will find a greater number of understory trees. If overstory trees are large, the forest is likely older. With that said, determining the age of a forest is a nuanced endeavor since trees, like people, behave individually. Some tree species grow faster than others, and even trees of the same species grow at different rates and to different sizes.
Matt encourages Gardens members to look up at the tree canopy.
“BARK”ING UP THE RIGHT TREE
You can learn a lot about trees at eye level, especially by examining bark. Bark plays several key roles in the life of a tree, including protecting its delicate inner layers from damage caused by weather, disease and insects, and providing holes known as lenticels, which allow the tree to breathe, exchanging gases including oxygen from the air. As a tree grows, the inner layers become too large for the outer bark to cover it, resulting in the outer bark cracking and splitting into distinct patterns and lines, which vary by species and can often help the observer identify the tree.
Does the tree have smooth bark? It may be a buckeye or beech tree. Does the bark split into vertical furrows? It may be an ash or oak. Horizontal furrows? Perhaps a birch. Does the bark crack into separate pieces, creating irregular patches? It could be a loblolly pine. Observing these bark patterns and more can reveal a lot about a tree.
Matt encourages people to pay close attention to bark patterns in relation to leaf type in warmer months so we can start to correlate the two identifying characteristics. Building that knowledge will come in handy when identifying leafless deciduous trees in winter.
The bark of a red maple (Acer rubrum) at eye level. Interestingly, red maples have smooth bark when young, and thus older trees look very different from younger ones.
REMEMBER M.A.D. BUCK
As we approached a large yellow buckeye (Aesculus flava) on the tree walk, we observed the tree’s smooth bark, a telltale characteristic of the species. But Matt was quick to point out that the buckeye’s next-door neighbor, a similarly sized tree with similarly smooth bark, was not a yellow buckeye but a bigleaf magnolia (Magnolia macrophylla). In warmer months it’s easy to distinguish these trees by their leaves, but in colder months it’s a challenge. How can you tell the difference? Matt recommends observing the tree’s branching patterns.
The yellow buckeye (Aesculus flava) at left and bigleaf magnolia (Magnolia macrophylla) at right have similarly smooth bark patterns.
Trees have two primary branching patterns, opposite and alternate branching. Trees with opposite branching have branches that grow directly across from each other in a way that looks like they are growing in pairs. Trees with alternate branching have branches that are staggered along tree limbs, alternating back and forth. Most trees in our area have alternate branching, but a few key types have opposite branching, namely maple, ash, dogwood and buckeye trees. Matt uses the acronym-abbreviation mashup “M.A.D. BUCK” to remember them (maple, ash, dogwood and buckeye). Sure enough, the yellow buckeye we observed had opposite branching, while the bigleaf magnolia had alternate.
Opposite branching on a yellow buckeye (Aesculus flava).
LEAVE THE LEAVES
While deciduous trees may lose their leaves in winter, leaves shouldn’t be discounted as a key identification factor in any season. You can often look at the ground around a tree to observe its fallen leaves. As we continued the tree walk, Matt invited us to look around the bigleaf magnolia to find its characteristic extra-large leaves. And indeed, at up to 20 inches long, they were hard to miss.
Observing fallen leaves around the base of a tree, in this case a bigleaf magnolia (Magnolia macrophylla), can help identify the species.
Plant identification plaques are also handy!
LOOK FOR STANDOUTS
Some native tree species are winter standouts for their singular features. American beech trees (Fagus grandifolia), for example, hold their golden-brown leaves all winter instead of dropping them. The cause of this phenomenon, known as marcescence, is not fully known, but scientists hypothesize that it may help protect overwintering buds from grazing animals and/or provide nutrients to the tree when it needs them most—when the leaves finally drop in spring, there’s a greater likelihood that they will remain and decompose around the base of the tree. Whatever the case may be, if you see a tree with brown leaves in winter, it’s most likely a beech.
Similarly, if you see a tree with sharp thorns on its trunk and branches, it’s likely a hawthorn, black locust or honey locust tree. Thorns are thought to be a holdover from the days of megafauna, when trees used sharp thorns to protect themselves from large grazing animals. Look for these standouts and you will be sure to impress people with your tree ID skills.
Matt points out the distinctive brown leaves of an American beech tree (Fagus grandifolia).
DON’T FORGET THE CONIFERS
While it’s somewhat easier to identify conifers like pines, firs and hemlocks by their foliage in winter, it can be difficult to distinguish between visually similar evergreens when they soar high into the canopy. Matt recommends turning to cones when in doubt. He led tree walk participants to two pine trees situated next to each other in the Blomquist: a loblolly pine (Pinus taeda) and shortleaf pine (Pinus echinata), both found in many Southeastern U.S. forests. Due to their height, comparing the trees by needle length was a big challenge, so we looked instead to the cones scattered under each tree. Loblolly cones, which are approximately 3 to 6 inches long, are noticeably larger than shortleaf cones, which are 1 ½ to 2 ½ inches long. By comparing cones, it was easy to differentiate between the pines. Problem solved! We then walked to a nearby eastern hemlock tree to observe its noteworthy diminutive cone measuring around a half to three-quarters of an inch long.
A loblolly pine (Pinus taeda) and shortleaf pine (Pinus echinata) soar into the canopy.
The loblolly pine cone, left, is larger than a shortleaf pine cone, right.
IT’S A-OAK-KAY TO GIVE YOURSELF A BREAK
Matt reassured us that it’s OK if you can’t determine the exact species of a tree through observation, especially when it comes to oaks. With 400 to 500 species worldwide, 90 of which are found in North America, oaks are one of the most diverse families of trees. What’s more, the Triangle region has one of the most diverse populations of oaks in the world. If you can’t identify a red oak (Quercus rubra) from a scarlet oak (Quercus coccinea), don’t worry. It’s hard for even the most seasoned professionals.
A leafless overcup oak (Quercus lyrata) in the Blomquist Garden of Native Plants. Photo by William Hanley.
Learn how buds, bark, evergreens and leaf scars also aid in winter tree identification in this article by Katherine Hale.
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We would like to extend a huge thank you to Matt and everyone at Leaf & Limb for their ongoing support of Duke Gardens. As a Gardens corporate member, Leaf & Limb plays a vital role in helping us keep the Gardens growing, now and into the future. We are sincerely grateful for their generosity!
To learn more about corporate membership at Duke Gardens, please click here.
And stay tuned for more member walks and events like this throughout the year! In fact, Matt will be back with another tree walk for Gardens members on April 26 to help us celebrate Arbor Day. For more information, please email GardensMembership@duke.edu.
All photos by Lauren Smith Hong unless otherwise noted.
