Seasonal Tips for 2008
(Fall)
April | May | July | September | October
Fall Foliage Season
Did you know that there are few places on our planet that have such vibrant foliage color that is produced by deciduous trees? Other parts of the world do have deciduous trees and they do go through the process of seasonal change but their colors are often dull and almost fluorescent. Why is this?
There are several factors that contribute to the beautiful fall foliage that we who live in North America are lucky enough to experience each fall. However the key element that stimulates great color is climate. Fall color, that is great fall color, results from a combination of crisp, cold nights and clear sunny days. Days of abundant sunlight are important. The display is not so great if the weather has been gloomy, overcast, and wet. Of course those trees that are planted in the open full sun will give the best display as opposed to those planted in the shade and overcast by other trees, especially evergreens. Other contributing factors like early near-freezing temperatures, drought, and low nutrient levels help to speed up the process and why autumn colors are at their BEST when the weather is bright, sunny, dry, and nights are cold.
The theory of autumn leaf color and change has been studied quite extensively by scientists at the university of Wisconsin-Madison. The chemical process of why leaves change color, how, and to what extent of the vibrancy has been studied by horticulturists like Bill Hoch, one of the co-authors of the phenomenon “Trees need to store as many of those nutrients as they can before the leaves drop.” He states that “North American trees produce high levels of anthocyanins” These are the pigments that produce red leaves and purple colored leaves and are produced by a combination of all these pigments plus another class of chemicals called tannin.
Hoch states that this is probably why European trees are not as vibrant as North American trees. They do not produce the same high levels of anthocyanins. He states that “We think it’s because the weather in that part of the world is cloudier and warmer during fall. European species don’t need the protection from light that is too bright like that of North America. These pigments are like a sunscreen and shade the important sensitive photosynthetic tissues that need to be stored before the leaves drop.”
Not to get too technical, but each color is produced by different chemicals which create the different colors of yellow, orange, red, and even purple. Because not all leaves have the same pigments and the right chemicals to cause color, some leaves just turn brown and fall off. Evergreens contain no pigments and stay green all year.
Why are leaves green anyway.... During the spring and summer months chlorophyll is present in maximum amounts which contribute to the green color. As the growing season slows down and the new chemicals take over with the abscission process (described above), the chlorophyll is blocked and the green color is diminished and replaced by pigments that create fall colors.
Chemically, how does this work. The first part of the leaf to turn color is the upper side that is exposed to the sun. The change in color is caused by what is known as abscission initiated by changes in the day length or number of hours of light each day.
During the spring and summer or growing season the tree absorbs water and nutrients thru the roots, the trunk, and up into the branches, into the petioles of the leaves and then into the leaves themselves. As our summer progresses and the fall begins to arrive, the days become shorter, the trees almost have an inert system that tells them that it is time to get ready for winter. The petiole almost shuts down and water and nutrients are blocked from the leaves – thus the leaf either turns brown and falls off or displays a lovely color anywhere from yellow to orange to red, purple and combination of these colors - then falls off.
Here in New England the peak season for what we call leaf peepers is around Columbus Day – October 13th this year – usually around the second week of October.
What Trees Produce the Best Color
I guess this is a matter of preference; and it takes a nice Sunday Drive to take in the real selection. The combination of trees produces the best color for me, not just one tree. However, I have the most incredible Sugar maple that is already producing a combination of yellow to orange to red. It is a sight to behold
- Yellow – Sugar maple, Redbud, American yellowwood, Ash, Ginkgo, Tulip tree
- Red – Red maple, Sourwood, Scarlet oak, Northern red oak
- Orange to Rust – Sugar maple, Bald cypress
- Mixed – Dogwood, Sumac, Smoke tree, Sassafras, Sweet gum
Remember, this is also a good season to plant trees. The fall color lends to the added value of planting a tree that displays fall color within your landscape. Once the leaves have dropped, other features like bark and trunk color and tree structure, and berries produced by such trees as Stewartias, Dogwoods, Zelcovas, and many others trees and shrubs may help your decision on selection. Visit your local nursery where there is a variety of specimens to view.
"There ought to be gardens for all months in the year, in which, severally, things of beauty may be then in season." - Sir Francis Bacon