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Monday - December 19, 2011

From: Houston, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Planting, Trees
Title: Live oak leaves turning yellow after planting in Houston
Answered by: Barbara Medford

QUESTION:

We bought a 65 gallon live oak in early October, and have been watering fairly heavily three days a week. It seemed OK, then all of a sudden lots of the leaves are turning yellow. Is it getting too much water, or not enough water? It seems that the water is just running off the surface and not going down in to the soil. We did put in root stimulator and fertilizer stakes. Thank you! Johannes

ANSWER:

First of all-WOW! A 65-gallon live oak? What did it take? An eighteen-wheeler and a crane? That is, frankly, a fairly risky and probably very expensive operation. It is almost undoubtedly suffering from transplant shock, which is not always fatal, and could have been caused by several different factors.

Risk Factor No. 1: We always recommend that woody plants, shrubs and trees, be planted in December or January, unless the ground freezes where you live. The ground does not freeze in Houston.

Risk Factor No. 2: Was the hole a really big one to accommodate as many roots as possible?

Risk Factor No. 3: Was the hole amended with compost to improve the drainage?

Risk Factor No. 4: Was the tree delivered to you in a 65-gallon pot or was it  dug up, bound and burlapped and delivered fresh out of the ground? If it has been in a pot very long, it would very definitely be at risk of being rootbound, in which situation the roots have grown round and round in the pot, eventually to strangle the tree. In a smaller woody plant, it usually is possible to do some root pruning to prevent strangulation, but we really are not sure how to deal with a tree that big.

Risk Factor No. 5: And this is the scariest one, at least to us. You stated that the water was running off the soil. If that is true, you have wasted a whole lot of water, the soil was not properly prepared for drainage so the water could soak in and not drown the roots;  the tree is suffering from thirst. Begin by making it possible to get a hose down in the dirt around the roots in several places and, as big as that tree is, probably some holes close to the trunk and some farther out. Stick a hose as far down in that hole as you can get, and let the water dribble slowly in each hole until the water starts coming to the surface. This time of year, once a week is about right. Mulch the soil around the base of the tree, without allowing the mulch to be piled against the trunk.

Risk Factor No. 6: This is related to No. 1, planting at the wrong time. One of the main reasons we recommend that oaks, especially the very vulnerable live oaks, be planted in December and January is that the nitulidid beetle, which spreads Oak Wilt, is not active in the coldest months. You need to be very careful not to damage the bark. When the bark is damaged, it exudes sap to which the beetle is attracted and, if he has been feeding on an infected tree, he will carry the Oak Wilt fungus on his body and infect your tree. For the same reason, if any pruning is done, pruning paint should be applied to any pruning wounds on branches larger around than your thumb.

And, finally, Risk Factor No. 7: If this tree was purchased from and planted by professionals, you need to get them to your tree yesterday to see it and determine what is happening and how it can be helped.

And don't fertilize any more, at least not now. Fertilizer urges a tree to put on more leaves when that tree is just trying to survive. Read this article on Iron Deficiency Chlorosis of Shade Trees. Yellowing leaves are often the result of chlorosis, or lack of chlorophyll (which makes leaves green). This yellow is usually the due to some necessary minerals being unavailable in the soil which can be the result of an alkaline soil or poor drainage in the hole.

Here are some pictures of chlorotic oak leaves.

 

 

From the Image Gallery


Coastal live oak
Quercus virginiana

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