by Larry Williams, UF/IFAS Horticulture Agent
As summer changes to fall, the shorter day length and cooler weather bring on changes in our shrubs, trees and lawns.
Evergreen plants such as azalea, gardenia, holly, camellia, cherry laurel and magnolia may lose older leaves on branches near the center of the plant during late summer through spring. There is no need for alarm by the loss of older, mature leaves during this time. This is the normal aging of older leaves.
However, be careful to not confuse this normal process with spider mites, scale, lace bugs, nutrient deficiencies, poor growing conditions, salt injury, etc. Just keep in mind that this normal change in leaf color and leaf drop occurs on the older leaves generally during cooler weather – it’s a seasonal change.
If the younger leaves, those nearest the tip of the shoot, turn yellow or brown there is cause for concern. Poor drainage, lack of water or alkaline soils may cause this condition.
Leaves of sycamore trees change from green to brown late in the season. This phenomenon is not caused by a change in day length or temperature. It is the result of sycamore lace bugs feeding on the leaves. This will take care of itself since sycamore trees will soon be dropping their leaves.
We also have some trees that exhibit beautiful fall foliage in North Florida. A few to consider include hickory and gingko for their bright yellow fall foliage, black gum for its early display of brilliant red, purple or orange leaves and red maple or Florida maple with their yellow or orange to scarlet red fall leaves. This seasonal change in foliage color is due to a combination of cooler temperatures and shorter days causing the green plant pigment chlorophyll to breakdown while other pigments become visible. Xanthophyll pigments result in some of the yellows, while carotenoid pigments are responsible for orange and anthocyanin pigments cause some of the red and purple colors seen in many fall leaves.
Our lawns also experience seasonal changes. Growth rate of lawn grasses decreases in fall. Not only does this slowdown in growth result in less required mowing but it also results in lawns not being as attractive as they were during spring and summer. Weak, thinning and damaged areas in the lawn will show little to no improvement during this time because of this slowdown in growth.
Some of our lawn grasses will exhibit reddish purple blades intermingled with mostly green blades throughout the lawn as a result of cool fall temperatures. Most lawns will normally turn brown with the arrival of the first killing frost in unprotected areas.