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It’s In Your Nature: Fall is not leaving before we enjoy it

My nature notes remind me that I can expect the “best” fall foliage palette between Oct. 15-20. That can vary a bit each year, and since I lived in lower Carbon County, I based my observations on that. The elevation of the Pocono Plateau may see the peak foliage a few days earlier. I thought I would use this beautiful time of the year to explain a bit about leaves.

Our vascular plants (those with water carrying structures) rely on leaves to survive. Leaves contain chlorophyll (green pigment) that allows them to capture the sun’s energy. This process is called photosynthesis. Leaves’ main job is to make food for the plant to grow. Leaves capture sunlight and through their stomata (tiny holes in the leaf) they take in carbon dioxide from the atmosphere. With the energy captured from the sun, the carbon dioxide is combined with water to form sugars providing the leaf, stem, and roots food. We also know that leaves, as a by product of photosynthesis, release oxygen back into the atmosphere through the same stomata. This oxygen is needed for all animal and plant life on earth to survive.

A leaf is usually a blade (Lamina) attached to a stem/branch. The stalk-like part of the leaf is called the petiole. In autumn, cells form at the junction of the petiole and branch resulting in lack of water to the leaf and leaf color change. We are most familiar with tree leaves (maples, etc.) but cacti have adapted with green trunks and leaves that are modified into spines for protection from moisture seeking animals. Conifer leaves are modified into needles. They have less surface area and thus can remain on the branch over winter.

Leaves have an epidermis to protect them from the elements, much like our epidermis does. Leaves also have different edge margins that aid in identification. Some are toothed and some smooth or rounded. Maples or oaks have simple leaves (one leaf on a petiole) while sumac, hickories, or walnuts have compound leaves. Those leaves have multiple leaflets on a petiole.

As we approach my second favorite season of the year, autumn, our area is blessed with a wide array of leaf colors drawing many visitors to this region to enjoy the brief nature display. These fall leaf colors are attributed to the slow death of chlorophyll and when the green slowly disappears, the other pigments “show off.” The yellows of sweet birch are from carotenoids (yellow and oranges) while the reds of sumac or red maples are from the anthocyanins.

Get out there in the next few weeks to observe the gradual change in colors and the eventual shedding of leaves as the trees prepare for the harsher winter conditions. Enjoy what the Times News region has to offer us. We are fortunate.

Test Your Outdoor Knowledge: True/False: A white pine’s needles are held for 2 years before they are “shed.”

Last Week’s Trivia Answer: The majority of peregrine falcon nests are now on tall building ledges or under major bridges spanning large rivers/bays.

How can you not enjoy autumn in the Times News area? The scarlet oak displays, in my opinion, the deepest red pigmentation (anthocyanins) than any other tree here. Fabulous color!
Sweet birch, a common tree usually favoring north sides of ridges, displays bright yellow foliage in early October. Note the leaves have a serrated margin - serrated means tooth-like edge.
Witch hazel leaves have arcuate venation (vein pattern) with sinuate margins - more rounded than the tooth-like birch leaves. Note the flower buds reminding you that they flower in October which is quite odd for any tree. BARRY REED PHOTOS
White oaks have lobed leaf margins. They probably have still not revealed their anthocyanins (red colors) yet because the chlorophyll remains alive later into autumn than the beech, birch or maples.
Alders, usually growing in damp areas, have leaves with pinnate venation - pinnate refers to feather-like.
Red oak tree leaves have cleft margins (not rounded like white oaks.) They will soon turn red and quickly die after that, revealing the tannins - brown coloration of the dead leaf.
Most common from northern Carbon County, and farther north, are sugar maples. Their bright orange pigment (carotenoids) rival my favorite scarlet oak foliage.
Evergreens, really a bit of a misnomer. White pines retain their newest needle growth throughout the winter. But, they shed much of the 2- or 3-year-old needles each October. Who hasn't enjoyed placing their picnic blanket on that soft bed of shed pine needles?
Our trees have simple or compound leaves. Shagbark hickory has compound leaves with five leaflets. Walnuts, ash, or sumac may have seven, nine, or more leaflets. This photo shows the hickory nuts that drop in September.
Probably dominating our forest colors this weekend will be the very common red maple; but I don't tire seeing its gorgeous red leaves. I always head into “Penn's Woods” the morning of the first heavy frost or freeze to watch the leaves drifting down by the thousands to briefly color the forest floor red as well.
Sassafras trees have 3 types of leaves on each branch. They have entire, 2 lobed, and 3 lobed leaves. They are not “painful” to look at either as they are also in peak colors this week.