How can we keep our aging dogwood tree (Cornus florida) alive?
It was a volunteer, with a handsome upright form, but lately it has lost branches and part of its crown and is looking sparse and sad. We have kousa dogwoods but I'd like to keep this flowering dogwood going as long as we can, and to replace it, if necessary, with another flowering dogwood--preferably with a similar upright shape.
Answer
Margaret, it is possible that your dogwood has a borer as the top is dying. Usually anthracnose kills a whole side branch, starting from the bottom up, but of course there are exceptions. To see if it has a borer, carefully start examining the trunk just below were the dead branches are occuring. Look for any kind of hole, and it may or may not have sap coming out of it. If you find a hole, stick a metal skewer in the hole and poke it up and down just under the bark, as this is where the borer usually has his tunnel. Then, wearing rubber gloves and a mask, squirt an insect spray into the hole. If you can, seal the hole with a piece of wood or something similar to keep the product in the hole. And remove the dead branch above. Then fertilize the tree at the drip line with a liquid made from Miracle Gro for acid loving plants. If you fertilize, do it now so any new growth has time to harden off before winter. I have planted the Cherokee Chief Cornus florida and so far it is lovely and not damaged. They do like moisture,, part shade, not exposed sites. Following is a link about the Rutgers hybrids between C. florida and C. kousa. I have grown several of the Stellar series which don't seem to have any problems yet. http://agproducts.rutgers.edu/dogwood/history.html. Best of luck!