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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Sunday - February 28, 2010

From: Jacksonville, FL
Region: Southeast
Topic: Diseases and Disorders
Title: Problems with dogwood tree in Jacksonville FL
Answered by: Barbara Medford

QUESTION:

Sir, I believe I have a Cornus drummondii, a stiff dogwood tree on my lawn which a few years ago was big, lush and full of branches and leaves. In the last 2 years I have noticed about 80% of it drop its leaves and no growth has been noticeable. Now, I have one area of the tree which is thick and green like it should be and the rest look like the winter got it.. I have watched it (sadly) go through this and hate that I cannot figure out what is wrong. I see that the 'dead' areas are starting to show new buds and blooms, but I need to KNOW what is wrong with it so I can save it and restore it to its natural beauty! As a side note, I have photos of what I am referring to.. also, it used to be inside of a 10 x 10 mulch bed, but with the lawn growing in to the bed every summer I took out the border and allowed the grass to fill in under the tree; I wonder if this is a factor too.

ANSWER:

We are not plant pathologists and diagnosing problems with a plant at a distance is nearly impossible at best; however, we will try to find some clues to help you play detective. First, you say you "believe" that what you have is a Cornus drummondii (roughleaf dogwood). Go to this page on roughleaf dogwood from our Native Plant Image Gallery and compare the pictures of berries, leaves and flowers with your plant. If your plant's characteristics don't match our pictures, you could use the photos you have to send them to us so we can try to identify the plant. Go to our Plant Identification page for instruction on how to send these photographs. 

Assuming we have the right plant, our Native Plant Database does not show this plant as being native to Florida, nor does this USDA Plant Profile show it growing there.  It does show it growing in several other southeastern states adjacent to Florida. In the nearest state, Georgia, it only grows in the farthest northwest corner. Since Jacksonville is in the northeast corner of Florida, with a USDA Hardiness Zone of 8b to 9a, the hardiness Zone 4 to 9 for this dogwood should not be a factor.

From our webpage on Cornus drummondii (roughleaf dogwood):

"Soil Description: Dry to moist, alkaline soils. Limestone-based, Sandy, Sandy Loam, Medium Loam, Clay Loam, Clay, Acid-based, Calcareous.
Conditions Comments: This is a very adaptable plant and is found in nature in a variety of wet to dry situations. However it grows best in moist soils. The large showy clusters of tiny flowers provide nectar for many butterfly species. Many birds eat the white fruit clusters. Leaves turn red in the fall. Dogwoods can be afflicted with many disease and insect problems, but most of these are not serious if the plants are kept in good health."

We give you these descriptions of growing conditions so you can, again, compare the soils and conditions you have in your garden to those this plant likes. Its sun requirements are part shade, which we consider to be 2 to 6 hours of sun a day, to shade, less than 2 hours of sun a day.  Finally, to get some help closer at hand, we suggest you contact the University of Florida Extension Office for Duval County. If others in your area are growing dogwood, and something is attacking them, the people at the Extension Office should know about it. 

Having exhausted the other possibilities, let's talk about the grass beneath the dogwood. Ordinarily, you would not think that understory grasses would  be a threat to an established woody plant. However, the way that grass is treated could be. If someone has been spraying herbicides or pesticides on that grass or in the area, that could certainly account for the leaf drop. Furthermore, excessive lawn fertilizer, which is high in nitrogen, can also affect the plant. 

From our Native Plant Image Gallery:


Cornus drummondii

Cornus drummondii

Cornus drummondii

Cornus drummondii

 

 

 

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