Monday, September 7, 2015

Fall Leaf Drop

Horticulture Hotline 09/07/15
By Bill Lamson-Scribner

A little cool some mornings, but the beautiful days continue. Rain, rain, rain. Mushrooms in lawns have become a hot topic. Do not eat them and everything will be fine. Have you put out your preemerge for those bothersome winter weeds? Have you fertilized your lawn, shrubs, and trees one last time? Have fall army worms chowed on your turf? Have the mosquitoes driven you indoors for the fall? With this rain, have you preventatively applied a fungicide for your lawn in those areas you usually get fungus?

Gardenias, Azaleas, Magnolias, and many other evergreen plants are losing some of their leaves. Although these plants are evergreens, they still have some natural leaf drop this time of year every year. Crape Myrtles, River Birch, Drake Elms, Willow and Sycamores are a few deciduous trees that can begin leaf drop early depending on the health of the tree.

Since the chlorophyll has left the leaves, people often mistake the yellowing of the leaves as a nutrient deficiency (most commonly iron) or think their plant is going into a decline. The chlorophyll is the “green” of the leaf, and usually masks the other colors of the leaf. Maple leaves turn red in the fall because the chlorophyll that usually masks the red color goes away leaving the red color behind.

As the chlorophyll leaves the leaf, bacteria and fungi grow on the leaf because the leaf is starting to drop from the plant and the leaf is not actively growing to ward off attack of these secondary invaders. At Possum’s we get a lot of calls from people that feel like their plant has a disease because of the leaf spots on the leaves that are getting ready to fall off of the plant. There is usually no reason to treat these leaf spot diseases that are attacking a leaf that is getting ready to fall off the plant anyway. These diseases are different from the diseases that attack an actively growing plant.

If you have a plant that is dropping leaves especially if it is a new plant, check to make sure it was not planted too deep. Established plants can end up being “planted too deep” because of mulch accumulation over the years. When I worked in Hilton Head, I was involved in a large project at the Lighthouse where azaleas were dying in large quantities from too much pine straw being applied year after year. 

Most plants do not like wet roots. If you have a plant that is dropping leaves, check your drainage, and be sure the plant is not getting too much water or the soil is too clayey.

A well fertilized plant will usually have less leaf drop. Looking at crepe myrtles and azaleas really illustrates this fact. You have to be sure you are looking at the same varieties of plant, and you can see a huge difference in crepe myrtles in August and September depending on the fertility program they are on. Now is a great time to soil test to get ready for 2016.

I’ll leave you with that!!