Autumn has officially begun and with it comes football games, chilly air and the annual display of red, orange and yellow leaves. Autumn foliage is a welcome sight, and for many, helps connect us to the natural cycle of the seasons. People often travel to witness the magnificent color changes in our forests, fall tourism can generate billions of dollars of economic activity across the country each year. But this year, Jasper County and much of the state of Iowa may experience a more muted display of fall colors.
This summer’s drought has reduced soil moisture for our crops, lawns and forests putting stress on those plants. Iowa State University Extension Urban Forester Gabbi Edwards explains how dry weather may have an effect on fall colors.
“Dry weather and drought will often cause trees to lose their leaves before color starts to show. The fall foliage colors will display for a shorter time, instead of peak viewing time lasting three weeks some places might only display colors for one week. The fall foliage colors will also be less brilliant than normal with colors appearing muted and dull,” Edwards said.
During a typical year peak fall colors for Jasper County will occur during the first through third weeks in October according to the Iowa Department of Natural Resources’ website.
The colors are actually pigments in the leaves, which are responsible for capturing the sun’s light and converting it into energy for the plant to use. In preparation for winter, the green pigments in the leaves break down allowing for other colors to show.
Edwards describes how drought can affect this process, “Early color change is typically due to environmental stresses with drought being a major issue this year. With decreased amounts of available water the trees will begin to go dormant earlier in the season. Color change is caused by the chloroplasts (structures inside leaves that produce chlorophyll) breaking down and ceasing production of chlorophyll, which gives leaves the green color. When chlorophyll production stops, other pigments are able to show through such as carotenoids which appear as yellow and orange. Trees also produce another pigment called anthocyanin in the late summer which display as reds and purples. Drought stress causes trees to cease production of chlorophyll earlier in the year, resulting in earlier displays of carotenoid and anthocyanin (yellows, oranges, reds and purples).”
Many concerned homeowners in Jasper County have contacted the ISU Extension and Outreach office for information on how to care for their drought-stressed trees. Mature, well-established trees will likely be unaffected by one year of drought. Though steps should be taken to care for newly-planted trees less than two years old. In dry weather, the root ball of young trees should be thoroughly watered every seven to 14 days throughout the fall until the ground freezes.
Edwards lists some additional steps homeowners should take to maintain their trees in the fall and winter, “Refresh the mulch around your trees, ensuring the mulch is two to four inches deep and ideally out to the dripline. Mulch retains moisture, prevents damage from a mower/weed whacker and insulates against temperature extremes. Young smooth bark trees such as crabapples, linden and maples can benefit from a trunk wrap but be sure to remove the wrap after the last freeze to reduce damage from insects and disease. Homeowners can also lightly prune trees in the late fall or early winter however most pruning should be completed during late winter (December through February). Utilize a warm fall day to evaluate your tree canopy and use flagging to mark limbs for removal in the late winter, that way you won’t cut the wrong limb!”
Even though 2017 will not be a record-breaking year for fall colors in our natural forests, with a little maintenance homeowners can ensure that the trees in their landscapes remain healthy for years to come.
Residents of Jasper County can contact ISU Extension and Outreach in Jasper County at 641-792-6433 for their home horticulture questions.