Why Does My Sumac Have Yellowing and Dying Branches?

Q. I have a 20-year-old sumac tree that has developed yellow leaves in several areas. There has been no change in watering or the soil. What is causing this and how can we treat it.

Branches dying in the bottom of the canopy of sumac. This may be due to too much shade. If not, it definitely contributed to the problem.

A. If the yellowing or browning of the leaves is occurring in shaded areas it might be because there is not enough light reaching the leaves. If the canopy is dense and creates too much shade then leaves and stems in these heavily shaded areas will die. When the leaves are first dying they turn yellow and finally brown when they are dead.

            Try removing some limbs on the tree to allow more light to penetrate inside the canopy. The problem is that African sumac responds very well to pruning with new growth and limb removal might have to be done regularly.

Regrowth or watersprouts coming from a large African sumac limb after removal.

            Do not remove too many limbs but allow the entry of filtered light inside the canopy.

            An easy way to see if enough light is entering the canopy is to look at the ground. If the ground beneath the tree is a solid shadow, not enough light is entering the canopy. It should be pixelated. Some limbs should be removed until the light on the ground is “speckled”.

            You can do this pruning any time of the year and do not have to wait for winter. I would focus on removing limbs around 1 inch in diameter and no larger unless the tree needs major pruning work done. Do major pruning only in the winter months.

            African sumac does not have very many diseases so I have ruled out the possibility of disease. At least in our desert climate.. It has a few insect problems but nothing serious except aphids which leaves a sticky or shiny appearance on the leaf surface.

            Aphids would be a problem in the spring and fall months. Heavy feeding by aphids could cause yellowing of leaves as well but they will be sticky. They can usually be removed with soap and water sprays.

African Sumacs Pretty but Messy

Q. I have two 20-year old African Sumacs in my back yard that drop nearly all their leaves every summer.  Every fall they always come back.  Is this normal?  Beautiful tress but make a real mess! 

A. African sumac is a messy tree. There is going to be a lot of leaf drop and the female trees will drop a lot of berries. The seeds in the berries germinate easily and you may see seedlings popping up all over the place.

African sumac in Bloom in February

Sparrows and mockingbirds love the fruit from the female tree and help to disperse new seedlings all over your neighbor’s landscapes. The male trees produce pollen that is pretty allergenic usually around February or March. These are drawbacks to African sumac.

African sumac in Bloom in February

African Sumac Needs More Water As It Gets Larger

Q. We planted an African Sumac tree three years ago that is showing a lot of new green leaves now. Could you please let me know how much water it needs? It was deep fertilized at the beginning of spring.

A. Are you sure you aren’t seeing flowers? These trees flower in late Fall and into the winter months in the Northern hemisphere.

African sumac flowers

You realize that trees require more water as they get older and larger. So at three years of age they require more water than when first planted. I would normally add another emitter at this age to give it the extra water it needs.

In another three or four years it will require again more water than it requires now as it gets even larger. You would add another emitter again at this time to deliver more water. You should avoid increasing the minutes to give it more water.

Two drip emitters will not be enough for a tree this size

With that in mind, I would estimate that after three years in the ground your tree should receive about 10 to 15 gallons each time you water if planted from a 15 gallon container. I can't give you that estimate in minutes because I don't know how much water the plant is getting in one of its minutes.

You should determine how much water is being delivered to the tree. I'm not sure if you're using drip or not but many emitters state the number of gallons per hour that it is delivering or they are color-coded.

Add all these gallons together and divide by the fraction of the hour you are watering; 15 minutes you would divide by 4, 30 minutes divide by two. Do not water landscape trees and shrubs daily. This time of year once a week should be adequate.

You can fertilize the tree yourself. Place some fertilizer underneath each emitter or use fertilizer stakes such as Jobes next to each emitter.

Jobes tree spikes

If you are watering in a basin around the tree, sprinkle fertilizer in the basin and water it in and save yourself some money. Don't put fertilize closer than a foot from the trunk.