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Trees Experience A Natural Sugar High
By Norman Winter
Central Mississippi Research & Extension Center
A sugar high may not be ideal in children, but our trees certainly have rewarded us this fall from the extra sugar in their systems. Mississippi trees are on a high from trapped sugar and are giving the prettiest color most of us can remember.
It was just a few months ago some of us were criticizing ornamental pears because many got caught in a spring epidemic of fireblight, a debilitating disease. Now the ornamental trees look like they are on fire with blazing crimson, orange and yellow all on the same tree. No one is complaining about the pears now, and they won't be in a couple of months when they are giving the landscapes pristine white flowers by the thousands.
When we look at fall color scientifically, words like carotenoids, pigments, chlorophyll auxin, gibberellins, other growth hormones and enzymes enter into the discussion.
Conditions for great fall colors boil down to cool night temperatures and warm, sunny days. The climate has the biggest effect on the production of anthocyanin pigments that intensify the red and scarlet colors. Conditions that favor these colors are sunny days and nighttime temperatures between 45 degrees and freezing.
Even though the chlorophyll content of the leaf declines in the fall, it is still important that photosynthesis take place. If an abundance of cloudy weather prevents photosynthesis from occurring, leaf color will be mediocre even if temperatures are ideal. This also can weaken the leaf, making it easy for a northern wind to blow it off the tree.
Cool night temperatures limit the movement of sugar from the leaves. It also reduces the rate of respiration in the leaf, so some sugars are converted to carbon dioxide. Those sugars retained are converted to colorful anthocyanin pigments, hence the sugar high connotation.
Even with perfect climatic conditions, if we don't have the best species of trees, we are lost from the start. Start with a good species. The trees that have been most spectacular in my neighborhood are the hickories. Hickories have bold, yellow leaves that hold for a long time.
Sweetgums are next on my list for fall colors. Its attractive palmate leaves provide some of the deepest shades of orange and crimson. My neighbors laughed when I bought one and planted it in my landscape, but no one laughs in the fall when it puts on a colorful show.
Other than hickories, the best trees for yellow are the green ash, gingko and elm. The best trees for red, in addition to sweetgum and ornamental pear, are the black gum, red maple, Japanese maple and the red oak that has been equally spectacular. Two others that we overlook are the dogwood and the new Indian varieties of crape myrtles.
One of the prettiest trees starting to catch on across the state is the Chinese pistache. This tree is used sometimes as a rootstock for the pistachio in California. It thrives in Mississippi and gives us some of our prettiest oranges and reds. It is a medium-to-small tree and will fit nicely in urban landscapes.
The Chinese pistache forms a spreading, umbrella-like canopy and attains a mature height of 40 to 50 feet with a width of 30 feet. This long-lived species should find wide acceptance for the landscape.
With good management, Chinese pistache grows 2 to 3 feet per year. Eliminate competition from grass or turf by applying mulch, proper fertilization and adequate water during the summer months. With such a growth rate, the Chinese pistache will reach a reasonable size and begin to play a major role in the landscape within just eight to 10 years.
These trees can be seen in and around Hinds Community College in Raymond as well as at strip malls in Jackson, in Grenada and along the Coast. While the ornamental pears sometimes break in the face of winds and ice, the Chinese pistache has an extremely hard, durable wood. Female trees produce colorful fruit suitable to use like holly berries in decorations.
Fall is a great time to purchase and plant trees and shrubs and more than likely would be a Christmas gift loved now and for years to come.