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Monday, October 7, 2013

African Sumac Limb Dieback Probably from Disease and Wet Soils

Q. I have attached a picture of my African Sumac.  The tree showed several branches with dead leaves so we started cutting back to a point where there was moisture and some green in the bark.
Should we continue cutting to make the resulting tree symmetrical or leave it alone and hope the tree recovers from our efforts?
African sumac from reader
A. I know there was not much you could do but the form of the tree is pretty much gone. African sumac sucker from cut shoots easily. Most of the suckering would occur within about 18 inches below the cut. You will probably also see some suckering further down on the limbs and trunk but it will not be as heavy. With the cuts made in September and October you might see some new growth over the next couple of weeks. Because the growth will be soft and succulent this time of year and perhaps not harden off very much for the winter, that growth may freeze back if we have some very low temperatures.

I would not make any more cuts this time of year. You do not want to encourage that kind of growth now.

However, I would suggest you consider waiting until the next spring growth and see what is alive and what is dead. When you can determine which of those large trunks are alive in the spring, go ahead and cut them back to the height where you would like to see new growth. From the look of your picture I would suggest you look at somewhere between three and 5 feet off the ground. You should start to see a lot of suckering below these cuts in the spring when there is normally no growth. Because this growth is not coming from existing buds on the tree, no growth may be delayed a few weeks compared to other plants that have not been pruned. As you see this suckering on the limbs, remove suckers that are too close together and those that are going perfectly vertical.

Why did the limbs start dying? Think of any changes that were made to the landscape in the past 12 months. In my opinion, there are perhaps three possibilities. The first to involve a lack of water or too much water. Both of them can cause limb dieback. If your soil is kind of heavy and does not drain water very well it's possible that standing water could suffocate the roots and eventually cause limbs to dieback. There is not much you can do about this if it was from those heavy rains earlier in the year or some earlier flooding event. I see you have wood mulch surrounding the base of the tree. Has that mulch been applied fairly recently? Mulches can really affect the moisture content of the soil and keep the soil moist much longer than if it is desert soil exposed to the open air.

I assume you were watching your watering but if your source of water was plugged for a period of time when it was really hot, that could cause limb dieback as well from drought. African sumac does not handle a lack of water very well and it does not handle too much water very well or poor drainage.

The third is possible disease problems. Again, at this stage there is probably nothing you can do about disease problems except what you are doing now and keep the tree as healthy as you can. I do not know of any specific disease or insect problems that will cause this to African sumac. I wish I could be more helpful and give you a specific answer but I can't.

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