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Oak (General)


August 4, 2018


I have a very large water oak tree (which is 27 years old) that has black streaks running down the trunk.  I was told it was worms and to put Vaseline in holes which I did.  Doesn’t seem to be helping.  I am afraid it is being eaten from inside and will lose tree if it is not properly addressed. 



Without seeing the tree, my guess would be wetwood, also called slime flux.  It is caused by a build-up of gas within the tree.  When we have a downpour following a dry period we commonly see a substance coming out of holes or cracks in affected trees.  The substance can be dark or white and frothy but it usually has a sour smell to it and can attract insects. Usually little damage is done to the tree but you can use a hose to wash it off the trunk.  We used to recommend drilling holes underneath where it was coming out to release the pressure and then put a pipe it to drain the liquid away from the trunk.  Research has shown that this practice is no longer necessary since trees showed no difference in recovery with or without the extra holes, which are also another wound to the tree.   


May 27, 2017

QuestionThis fuzzy looking polka dot growth is on the end of a leafless oak twig. I've never seen one like it. Do you know what it might be? 

Picture of Oak gall  


This is an oak leaf gall.  This particular gall was probably caused by a gall wasp.  The adult lays her eggs on the leaves and when the eggs hatch the larva gives off an enzyme that causes these unusual shapes on the leaves.  They can come in many different colors and can be solid or spotted.  While they look unusual they really don’t cause much harm to the trees at all.  While most galls are produced by insects there are a few caused by fungi as well. 


February 27, 2016


What is wrong with this tree? Please let me know as soon as possible, before storm season.



The problem is called smooth patch of oak. Smooth patch is actually a fungal infection of the bark. The infection is restricted to the outer bark, causing it to slough off, leaving smooth, depressed areas. This effect gives the bark a somewhat sunken appearance.   Since the patch fungi invade only the nonliving, outer bark tissues, this disease is not harmful to the tree and has no long term effects on either tree health or on structure.  No control is recommended for smooth patch other than keeping the trees healthy with regular watering when dry.



(December 2012)

Question Can you tell from this picture what is causing the bark on this oak tree to fall off? This tree looks like it is dying and we would like to know what might be causing it. The tree is on a home site with five acres of hardwoods and pines in West Little Rock.

AnswerYour tree has hypoxylon canker. This disease has been prevalent this year and will be next year as well--since it is common when a tree is drought stressed. Typically by the time the outer bark sloughs off, the tree is half dead or more, and you cannot reverse the trend. The underneath wood is either black and tarry looking or the gray powdery substance you have.

(November 2012)

Question Yesterday I was visiting a friend and noticed that all the oak leaves in her driveway were upside down. Today I noticed that my own driveway was full of upside down oak leaves. Interestingly not one of them was right side up. They have the lobular kind of leaves...maybe white oaks...not pin oaks. I am sure it has to do with the concave topside of the leaf and wind currents. I think it is kind of fascinating. What say you?

AnswerYou made me curious, so I went and looked at the millions of leaves in my yard, and I have a combination of up and down. I have never heard of the phenomenon before, but it is interesting.

(December 2012)

Question I have a question about an acorn that my sister picked up recently from one of the few trees to survive the fall of the towers in New York. I would very much like to plant it, but should I over-winter it in a container or something? We have lots of squirrels and don't want them to get at it.......What to do, help if you can?

AnswerThere are a variety of different types of oaks out there and germination rates will vary between species. I would recommend you get a plastic bag and fill it with moist potting soil—not wet, but about the moistness of a wrung out sponge. Put your acorns in the bag and put the bag inside your refrigerator for the winter. This is giving the seeds a cool, moist period called stratification—they would get this naturally outdoors, but you are preventing the squirrels and other critters from getting them. In the spring, pot them up and be patient. I would grow them in a container so you can monitor their growth. Once they are up and growing, if you know where you want to plant them, plant away.

(December 2012)

Question I have a question about some trees in my yard. I have a number of post oaks in my yard, and I am finding a growth of some sort on the underside of many of the leaves. I have attached a photo. Can you tell me what this is and whether it is a problem that needs to be treated? There are many of them, and I don’t find them often on oak leaves from other yards. I live in Fayetteville.

AnswerYou have a gall on the leaves. Galls can look frightening, but cause little damage, when on leaves. They can be hard shelled or fuzzy, and some even come with polka dots! Galls can be caused by insects or a fungus, but in this case it is caused by a small mite. They are nothing to be concerned about. Occasionally different species of galls form on small branches or twigs, and these can do harm, but yours is common on trees everywhere.

(September 2012)

Question If the bark is falling off from a part of a tree does that mean the tree has to be cut down because it is dying? Could it just be pruned up to remove the damaged part and the tree be saved?

AnswerIt depends on what is causing the bark to fall off, and the overall health of the tree. Sometimes lightning can hit a tree and cause bark to slough off—damage can be minor or deadly. Many oaks around the state are dying in part due to drought stress, but that can also cause hypoxylen canker to kick in. When this disease takes over, the outer bark usually falls off in patches, exposing either a dry gray substance or a black tarlike one. Usually by the time the bark falls off, the tree is either dead, or almost there. Damage from a weed-eater or lawn mower can also cause bark damage, but usually too close to the ground to cut out without cutting down the tree. Once bark begins to fall, you can’t stop it, but you can clean the wounded area and try to keep the tree overall healthy with proper watering.

(August 2012)

Question We will be expanding our front porch this fall, which will necessitate removal of a single low hanging branch from a nearby oak tree. Given the heat and drought of this summer, when is the best time to have it removed? The tree has been watered all summer and does not show any signs of distress.

AnswerIf you are just removing some lower limbs from established trees, there shouldn't be any issues. For small, young trees, we want extra foliage to help keep them established, but I think it will be fine to prune them as needed.

(October 2011)

Question I live in Cabot and my house gets full sun the entire day. I went to a tree giveaway and got a little fir tree, a red oak and a dogwood. Would any of those be good for backyard plants? Will the dogwood do well in full sun? All of them are very young trees! I am thinking of putting a red maple in the back yard with loropetalum and azaleas to hide the cable box. I have never lived in Arkansas and don't know your trees.

AnswerWelcome to Arkansas. Dogwoods would not do well in full sun all day—they would sunburn every summer. They are best in full morning sun or filtered sun. The oak tree is a wonderful shade tree and by fir, I am assuming you have a bald cypress maybe? It too will make a large shade tree. Red maples are great mid-sized trees. If you want one with guaranteed fall color, choose one now with color or go with a named cultivar.

(December 2011)

Question I am wondering if there is some scientific explanation for the huge increase this year in the amount of acorns that have descended upon our yard? We live in Bismarck, south of Hot Springs. I've been here since 1995 and of course rake the leaves and clean the gutters, and I can't recall ever having had so many acorns in the gutters and on the ground. I think they may have run their course, as far as falling, and there are still plenty is piles around the yard to dispose of. There were times a month or so ago when they fell in such volume and sound that the family thought it was a hailstorm!

AnswerWhite oaks produce acorns every year, while red oaks take two years to produce their crop. I think both trees have ample acorns this year. I am quite surprised at the volume, considering the two summers we just went through. I do think the size of the nuts is a bit smaller than they could be, and some dropped pre-maturely, but we do have a huge crop this season. Great for wildlife, but get ready next spring—if the acorns are viable, you will see tiny oak seedlings popping up wherever you left acorns.

(March 2010)

Question I am unable to determine if one of two trees in my front lawn is dead. Both, according to my neighbor, are white oak. One shed all of its leaves in the fall and is now appearing to form sprouts. The other did not shed leaves; they turned brown but still remain. Some of the leaves did fall with the strong winds and rains of the winter. It is difficult for me to determine if there is any sprouting. How long do I wait to see any greenery? With the advancement of springtime, I am anxious to begin working in the lawn, but am fearful that anything done might be upset if the tree has to be removed. I do want to save the tree if possible. I did call my local Cooperative Extension Service, but was advised to wait until spring, that there was no danger of the tree falling. It is very near to the house.

AnswerThe tree that did not shed its leaves is a concern, but you still need to be patient and wait to see if they leaf out this spring or not. We are having a late spring this year, so I wouldn’t make any decisions until mid to late April. Rarely does a tree die and decay enough to fall over in one season. See what happens this spring and then prune out any dead branches or trees. Any idea on what caused the problems? Any recent construction, grade changes, etc?

(November 2008)

QuestionAn observant colleague brought in some small wild-onion-bulblet looking objects this morning, saying they were all over her yard. They didn’t look like the fuzzy oak leaf galls I have seen before but when I went home to look at my own oak trees, I found the same little bulbs everywhere on the ground and on the oak leaves. Is this some kind of plant lice? Are they having a banner year after all our rain?

AnswerI have not had any unusual reports of galls forming late this season, but we have a variety of galls that form on oak trees every year. In fact, 60 percent of all known insect galls occur in the oak family. These growths may be the result of fungi, bacteria, or mites, but insects are usually the culprit. Gall-forming insects include aphids, phylloxeras, psyllids, midges (gall gnats) and gall wasps. They normally begin in the spring and then age throughout the season. If galls are cut open early enough in the season, you can often spot larvae, pupae and adults inside. The galls look worse than they are. They can be smooth or fuzzy, solid color or spotted. They can actually be quite interesting to look at, but rarely do they cause any problems. If you want to be certain, take a sample in to your local county extension office. At any rate, if they are falling, I would simply rake them up and be done with them for this season.

(September 2007)

QuestionWe are building a new house and there are no trees in the yard. Can you recommend a tree that gives nice shade and grows quickly? When is the best time to plant them?

AnswerThere are quite a few trees that grow quickly and make nice shade trees. Probably the fastest growing tree is the tulip poplar—Liriodendron tulipifera. This tree will be large at maturity, so make sure you have ample room for it to grow. Don’t plant a shade tree any closer than 15 to 20 feet from the foundation, and always look up to avoid power lines before planting. Some other good choices include: Lacebark elm – Ulmus parvifolia, Willow oak – Quercus phellos and Littleleaf Linden – Tilia cordata. In my opinion, the best time to plant a tree is in the fall. Planting in the fall as the trees are going dormant allows the root system to grow and get established without having to supply energy to the rest of the tree. This will give you a stronger tree once the growing season begins. Having said that, be aware that today many trees are containerized, and can be planted 12 months out of the year, as long as you are willing to water.

(July 2007)

QuestionWe live in Conway, near Beaverfork Lake. For 2 weeks we have noticed that our oak trees are infested with green caterpillars; some have brown stripes on them. The infestation is so great that entire trees are nearly denuded of leaves. It sounds like rain is falling and their waste is leaving brown stains on any hard surface. What are these caterpillars, and how long should we expect them to stay? Is there a chance that the trees will be damaged?

AnswerYou are not alone with this problem. We have had reports from all over the state about these caterpillars. Several have said their trees were raining poop! The culprit is the variable oakleaf caterpillar. They feed on a variety of deciduous trees, but tend to favor oaks, with the white oak preferred. In Arkansas we can have two generations of the insects, but with such a heavy first population, the chances of a second large population in August are slim. Their feeding cycle should be over now or coming to a close very soon, and they should pupate, typically on the ground. The larval or caterpillar stage produces a 1 ½ inch long caterpillar with the overall body color varying from green to yellow and red. The adult is a gray moth with a wing span no greater than 1 3/4 inches. While their feeding looks quite impressive, there should be no permanent damage from it. One theory about why the outbreak has been so significant this year is that many trees were damaged by the hard freeze in April and had more tender foliage on them. Whatever the cause, lets hope we don't have a repeat anytime soon. Sprays should not be necessary.

(September 2006)

QuestionWe built a landscape block flower bed approximately 12” high around a large red oak tree 2 years ago. My uncle said we would kill the tree because we used too much dirt and should slowly raise the amount of dirt in the bed. The tree died less than 1 year after we established the raised bed. I did have several red oaks die the previous year due to the "red oak borer insect". My question is this; can you build a raised bed around a mature oak tree without killing it? My wife and I have another tree that we would like to landscape, but do not desire to kill another tree.

AnswerI wish there were an exact formula for the total amount of soil you can build up around an existing tree. Unfortunately, there are too many variables, such as type of tree, soil type, size of bed, etc. As a general rule, we really don't recommend adding more than 1-3 inches of soil around an existing tree, and even that in a limited fashion. If the flower bed is relatively small, it usually isn't a major cause of concern. Keep in mind that a tree has an extensive root network, and that the feeder roots should be far and wide under a trees canopy. If the bed is small and not overly deep, I would suggest going for it. I would avoid piling up huge amounts of soil next to the tree trunk as excess moisture on the trunk can lead to decay.

(February 2006)

QuestionLast summer I was visiting Little Rock's Roselawn Cemetery and noticed several beautiful old oaks. I took a sample of the leaves and bark to a local nursery and no one could id them. I decided to make a special trip back in the fall when I knew the acorns would be falling and gathered up a hand full. What can I do to get them to sprout? I put a few in a pot inside but so far nothing has happened.

AnswerIt depends on what type of acorns they are. Different species vary by their dormancy needs—for example: white oak acorns need no pretreatment, while pin oak acorns need a stratification period (temps between 32 -41 in moist peat moss for 30-45 days). Since yours are not sprouting, my guess is you have acorns which require a moist, cold storage period. Put the pots either outside where it is cool or in a refrigerator. If you don't have room for the pot, dump the acorns and potting soil in a plastic bag. Make sure the soil is damp, but not wet. Put the bag in the refrigerator for 1-2 months. They get this cool, moist storage naturally outdoors if the squirrels don't get to them first. Once they have gone through the cool moist storage process, repot and wait for germination.

(November 2005)

QuestionI recently was assigned a parking spot under Pin Oak trees over in North Little Rock. Every day my car is covered with sap. Can you tell me what months of the year I can anticipate this happening, or is it all year long?

Answer- The problem is caused by aphids. These sap sucking insects really built up large populations this year at the end of the season--the dry weather added to the problem. As they feed on the foliage, they give off a sticky substance known as honeydew. It can be a real nuisance. Aphids can feed any time during the growing season, but often are at their worse in late summer through early fall, a drier season. Heavy rains and wind can keep them in check, since the insects are poor swimmers. You might try releasing some ladybugs in the area when the problem occurs, since ladybugs are prolific feeders of aphids. You can also spray with insecticides or even a strong spray of water on the lower branches--those in closest contact to your car.

(January 06)

QuestionI have a large white oak tree that needs some serious pruning. After the dry summer we've had will it be too stressful to prune it now?

AnswerHopefully, the tree was well watered this past year. Pruning shouldn't impact it too much as to water needs, but do utilize proper pruning practices. No topping! If you do thin some branches, be sure to prune to the branch collar and make clean cuts. Try not to remove more than one-third of the growth in any one season. If you are removing dead branches, you may need to wait until spring to be sure of what is living and what isn’t.

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