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.
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| 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.
Hi! I am in tears - I have (had) a gorgeous African Sumac that had grown exactly like I wanted it to. I went on vacation and when I came back saw that my gardener has cut all of the lower limbs of my tree!! Now, not only does it not spread out as far as it did, it also lost all of its lower branches which blocked my neighbors from seeing into my windows. Will those lower branches grow back!??!!
ReplyDeleteSee below.
DeleteShort answer is, “Yes.” The rate at which they grow back depends on the trees vigor and size. Too bad you didn't send me pictures, or I could give you a more definitive answer. You can send pictures to my email address at Xtremehort@gmail.com or morrisr@unr.edu.
ReplyDeleteThe vigor depends on its size or how long it's been planted in the ground. If the tree has been in the ground about 20 years, it usually is bit taller than 20 feet and 20 feet wide. Keep it healthy and well-watered. This means a tree 20 feet wide would need about 4 feet of water applied to the area of the soil under its canopy about 4 feet deep. That means the wetted area under the tree would be about 20 feet wide or about 400 cubic feet of water or about 3000 gallons of water in our Las Vegas area. Each application of water should wet the roots down to a depth of about two feet. In most soils that would be about 2 inches of water. We don’t want it to grow too fast when its big, but you have special needs. An annual fertilizer application is in the early part of spring is all that is usually needed.
In this case, fertilize twice a year to stimulate new growth. Let it regrow in this area. Don't let your maintenance company prune this tree. Fertilizer applications twice a year will cause it to grow more rapidly and fill in places you are concerned about. Use an all-purpose landscape fertilizer such as 16-16-16 or about 2 cubic feet of of a rich compost applied no closer than two feet from the trunk of the tree. Apply it the first time during the very earliest part of the spring and a second time just before it gets hot during the early part of summer. You should see it get denser by early next summer.
In the case of your tree, the second application will be about three to four pounds of fertilizer. If you used a rich compost then no more granular fertilizer is needed. Find the drip emitters at different locations just under the rock or woodchips and apply about one latte-sized cup of this fertilizer under 4 to 5 emitters. Make sure any rich fertilizer applied is no closer to than 24 inches from the trunk of the tree. Water from the fertilizer will be dissolved and feed the tree for about one month. Compost is slower to release nutrients toward the end of its life. The rich compost should slowly feed the tree through the spring and early summer months. If you use a rich compost instead of a fertilizer, alot more compost is needed than granular fertilizer. If you cant find a "rich fertilizer" then combine fertilizer with the ordinary compost applications for just the first application but cut the fertilizer in half for both applications.
Ist application in early spring...either one application of compost or one application of fertilizer.
2nd application to the tree use only fertilizer.
2 types of compost...rich (very high in nutrients and harder to find, high enough that it will burn plants)
Common compost....not as rich and much gentler when applying to plants.
Why are just some leaves on my african sumac tree turning yellow while the rest are lush green
ReplyDeleteIt may be from lack of nitrogen fertilizer. Try fertilizing the tree with straight nitrogen (such as 21-0-0 or ammonium sulfate) to push new growth and stop the trees from developing yellow leaves from green.
DeleteA second thing to try is controlling salt (or salinity) of the soil. Because African sumac has few or no listed varieties, the tree is started from seed and not grafted. It is usually propagated in the nursery from seed. Seedlings, as they are called, have a lot of variability compared to varieties. This includes sensitivity to salt.
The only thing that controls salt sensitivity is water and drainage. Your tree may need additions of compost (to amend or modify the soil and improve drainage) and water. Make sure you water the tree with enough water to wet the soil to a depth of 18 to 24 inches deep on mature African sumac. Make sure the water applied wets the soil to at least half the area under the tree’s canopy and to the appropriate depth.