CHAMPAIGN, Ill. - For many people, autumn weather brings a welcomed time of the year. Adding to the pleasure of the season are the vibrant colors displayed in nature. Leaf pigment, the physics of light, weather conditions, plant species, and geography all play important roles in the color of autumn.
Leaf Pigment and Light

Thanks to the physics of sunlight striking pigments in leaves, we see various leaf colors throughout the year. Leaf pigments play a crucial role in the colors we see. Chlorophylls, carotenoids, and anthocyanins present in a leaf help determine what color the leaf will display.

The pigment that gives leaves their green color is chlorophyll. Chlorophyll is used in photosynthesis which is the process that uses sunlight to transform carbon dioxide and water into carbohydrates (sugars) that fuel tree growth. During the spring and summer, with more hours of sunlight and warmer temperatures, this photosynthetic process is most active thus leaves are green.

The pigment that gives leaves their green color is chlorophyll. Chlorophyll is used in photosynthesis which is the process that uses sunlight to transform carbon dioxide and water into carbohydrates (sugars) that fuel tree growth. During the spring and summer, with more hours of sunlight and warmer temperatures, this photosynthetic process is most active thus leaves are green.

Unlike chlorophyll and carotenoids which are present in leaf cells throughout the growing season, anthocyanins are produced in autumn. Anthocyanins give color to familiar fruits such as cranberries, red apples, cherries, and plums. These complex water soluble compounds in leaf cells react with excess stored plant sugars and exposure to sunlight creating vivid pink, red, and purple leaves. A mixture of red anthocyanin pigment and yellow carotene often results in the bright orange color seen in some leaves.
Weather and Color

Weather conditions that occur before and during the decline of chlorophyll production can affect the color that leaves may display. Carotenoids are always present so the yellow and gold colors are the least affected by weather.

Colors most affected by weather are the red tones created by anthocyanin. On warm sunny days lots of sugar is produced in the leaves. Trees exposed to brighter sunlight generate the reaction between the anthocynanins and the excess sugar creating the bright red hue.

Cooler temperatures cause the veins in the leaves to gradually close preventing the sugars from moving out which preserves the red tones. Thus a succession of warm sunny days and cool crisp nights can paint the most spectacular display of color.

The level of moisture in the soil can also affect autumn color. A severe summer drought can delay the onset of color change by weeks. Ideal conditions for producing the most brilliant colors are a warm wet spring, favorable summer weather, and sunny fall days with the cooler temperatures at night.
Species and Geography

The genetics of different tree species help determine what color the leaves will turn. Color depends on the levels of iron, magnesium, phosphorous, or sodium in the tree and the acidity of the chemicals in the leaves. Some tree species displaying yellow foliage are ash, birch, beech, elm, hickory, poplar, and aspen. Red leaves are seen most often in dogwood, sweetgum, sumac, and black tupelo trees. Some oaks and maples present orange leaves while others range in color from red to yellow, depending on the specific species.

Deciduous forests and trees, with their many broad leaves that change color almost in unison, display the most noticeable fall color. Evergreen species also display fall colors, only slowly and gradually. The appearance of autumn color starts as early as mid September in more northern latitudes and moves southward, reaching its peak in October, but color continues to appear in more southern regions and higher elevations in the west throughout November.

Only a few places in the world have the combination of tree species and climatic conditions necessary for the most vivid fall foliage. Some of the best locations with broadleaved deciduous trees and favorable conditions for brilliant fall color are:

* Northeastern U.S. (New England)
* Southeastern Canada
* Adirondack, Appalachian, Smokey, and Rocky Mountain Regions
* Select areas around Seattle, Portland, and San Francisco.

Remember that cooler, higher elevations will display color before lower, warmer geographic regions.

Even with these facts, the timing, location, and intensity of autumn color are not completely predictable. To truly experience the colorful display, you must be adventurous. There are many states with thousands of scenic byways designed to focus on the palettes of autumn color. So even if you live in a region that does not produce an array of color, take an autumn vacation and explore nearby states that do. For up to date regional information, you may contact the U.S. Forest Service Fall Color Hotline at 1-800-354-4595 or on the internet at http://www.fs.fed.us/news/fallcolors/index.shtml.

The International Society of Arboriculture (ISA), headquartered in Champaign, Ill., is a nonprofit organization supporting tree care research and education around the world. As part of ISA's dedication to the care and preservation of shade and ornamental trees, it offers the only internationally-recognized certification program in the industry. For more information, or to contact a local ISA Certified Arborist, visit www.treesaregood.org.
CHAMPAIGN, Ill.?As the weather shifts and leaves start to turn color, you may think that your trees are going to sleep and can take care of themselves until spring.  But, there's actually a lot you can do for them now to make their transition into winter a smoother one.

"While your trees seem to be in a state of hibernation in the winter, exposure to the tough conditions can cause them major stress," says Jim Skiera, Executive Director of the International Society of Arboriculture (ISA). "Minimize stress by helping your trees through the cold months, a little at a time. If you take care of your trees in the winter, you'll be rewarded in the spring."

So, here are two small ways to make a big difference for your trees this fall:

Fertilizing

At times, it can be hard to determine if fertilization is necessary.  A homeowner's goal for fertilization should always be to supply nutrients determined to be lacking to achieve the best health for their trees without over fertilizing. An ISA Certified Arborist may be needed to help clarify reasons for a tree's failure to thrive.  However, basic guidelines for fertilization include :

·       Overcome a visible nutrient deficiency
·       Eliminate a deficiency that an ISA Certified Arborist detected through soil or leaf analysis
·       Increase vegetative growth, flowering, or fruiting of trees
·       Increase the vitality of the tree

Take note, however, that when a tree is not thriving, or is showing signs of stress, fertilization may not always be the answer.   Fertilizing a tree may not be necessary when:

·       An ISA Certified Arborist has determined that there are sufficient levels of all essential elements, and that growth rate and condition of the tree are acceptable
·       Potential pest problems have been detected
·       Herbicide may be causing residual damage to the plant

Some pest problems can be made worse with fertilizers.  Additional nutrients can increase pest populations or reduce the tree's ability to fight off the stress caused by pests.  Correct diagnosis requires a careful examination of the situation. Treatment depends on many specific factors. Responsible arborists practice "prescription fertilization" by only adding what is needed to reach your tree health objectives.  Over fertilization can be a source of ground pollution and effect nearby water sources.

Mulching

Urban landscapes are typically harsh environments with poor soil conditions, little organic matter, and big fluctuations in temperature and moisture?all "unfriendly" growing situations for trees. A two to four inch layer of organic mulch can mimic a more natural environment for trees and improve overall plant health.

To ensure the health of your trees and plants, follow these practical mulching tips to landscape like the pros:

·       For well-drained sites, apply a two to four inch layer of mulch. If drainage problems exist, use a thinner layer.
·       If mulch is already present, check the depth. Do not add mulch if there is already a sufficient layer (2 to 4 inches) in place. Instead, rake the old mulch to break up any matted layers and refresh the appearance.
·       Avoid placing mulch against the tree trunks.
·       If mulch is already piled against the stems or tree trunks, pull it back several inches so that the base of the trunk and the root crown are exposed.
·       Mulch out to the tree's drip line or beyond if possible.
·       Most commonly available mulches work well in most landscapes. Be mindful of the fact that some plants may benefit from the use of a slightly acidifying mulch such as pine bark.
·       Organic mulches are preferable for their soil-enhancing properties. Be sure it is well aerated and composted to avoid sour-smelling mulch.
·       Avoid using uncomposted wood chips that have been piled deeply without exposure to oxygen. Use composted wood chips instead, especially when they contain a blend of leaves, bark, and wood.

When you care for your trees, they will reward you for years to come.  For more information on tree care, visit www.treesaregood.org.