On the Topic of Turn…
The coming of fall brings on all kinds of changes, back to school, back to work, cooler temperatures, sweaters and boots, and trees turn. People flock from miles around to places known for their breathtaking fall foliage. “Leaf-peeping” is so popular there are tours available, special getaway packages and towns that depend on those tourism dollars. But what are we looking at? Why do leaves change color in the fall? All spring and summer leaf surfaces act as the factory producing food and energy for plants and trees. Cholorophyll-containing cells perform photosynthesis, absorbing the sun’s energy and using it to transform carbon dioxide into the sugars and starches that feed the plants. The chemical chlorophyll is the reason leaves are green, although within the cells reside other pigments such as xanthophylls, which are shades of orange, but are masked for the majority of the year by the massive amount of chlorophyll.
The changes in day-length and temperature that come with fall tell the plant cells that it is time to stop producing food and chlorophyll begins to break down; this means the green color begins to disappear allowing latent yellows and oranges to be visible. Additionally chemical compounds are changing which may result in the production of red anthocyanin pigments. Mixtures of these processes give way to all of the colors in between that make up the awe-inspiring fall splendor.
Weather and regional climatic differences will also affect fall color. Amount and intensity of light, temperature and soil moisture all influence the degree and duration of fall foliage. When temperatures are low, yet still above freezing the production of anthocyanins is favored but an early frost will weaken the brilliance of these reds. Overcast, wet days seem to increase the intensity of leaf coloration and the optimal day for leaf-peeping would be a clear, dry, crisp autumn day.
Fall seems to be over in the blink of an eye, so try to enjoy it while you can. Visit http://farmersalmanac.com/peak-fall-foliage-dates/ to find when the peak for fall foliage color occurs near you or to plan a leaf-peeping adventure.
Autumn is also referred to as fall because leaves literally fall off of trees, and this is just a fact of life with seasonal change…..but what makes leaves actually fall off of (deciduous) trees? When the signal is given to stop photosynthesizing a special layer of cells begins to develop at the point where the leaf stem is attached to the branch. These cells gradually cut off support from the tree, severing the tissue attached to the leaf. Concurrently the tree seals off the point of severance, when the leaf is eventually blown away or falls off, a small scar is left behind.
In northern regions most broadleaf trees are deciduous, meaning that they drop their leaves in the fall, although there are, of course, exceptions such as broadleaf evergreens like rhododendrons and holly. There are a few species of deciduous trees whose leaves cease producing food but they persist on the tree until the next set of leaf buds open and push them off; beeches and some oaks, for example. In southern regions, where winters are considerably wilder, many broadleaf species retain their leaves, with chlorophyll intact, year-round.