Ask Allen

Ask Allen ~ "Pruning 20-foot-tall Crape Myrtle"

Question:  Cheryl Wood: Please advise on how to get a Crape Myrtle back to a manageable height after reaching 20' tall.

Allen's Answer: Cheryl, Thanks for your question.  First, let's talk about what not to do. Many people plant Crape Myrtles in locations that, over time, become too large for that location. Then they top the tree, leaving unsightly stubs that, over time, create knots that produce numerous, weak new shoot growth. This causes stress to the tree, making it more vulnerable to pests and disease, along with the undesirable aesthetics it creates. Now, let us look at pruning your tree. 

Here are a few things to consider when pruning: 

• Never remove more than 1/3 of the branches. 
• Use the 3-D’s when removing branches: Dead, Diseased and Damaged. 
• If the tree must be downsized, do a crown reduction, using reduction cuts rather than topping as I described earlier. By doing a crown reduction with reduction cuts, this will keep your tree more symmetrical and will maintain a normal appearance.  Reduction cuts are made by moving down from the tallest limbs to a lateral limb (at least 1/3 the size of the limb you are cutting) and making your cut just above that limb. This will minimize new excessive growth, which causes weak limbs.  
• Heading cuts are the least desirable, and should only be used as a last resort when lateral limbs are not available. These are made by cutting the limb just above a node (i.e. - growing point). This will cause excessive growth, which is the reason it is not recommended.  

Good Luck. Crape Myrtles actually require very little pruning when the right size tree is planted in the right place. There are numerous sizes of Crape Myrtles, all the way from a shrub that only gets a few feet tall up to the large varieties.

To "Ask Allen" a question, email AskAllen@cityhs.net.  

Allen Bates is the City of Hot Springs urban forester, and he manages the City’s urban forestry care, preservation and health plan to provide the City with a safe, healthy environment for the City's urban forest. 

Ask Allen ~ "Wasps on Crape Myrtle black stuff"

Question:  Yvonne Fall: I rent this home and there is a Crape Myrtle outside the window of my office which also happens to be close to the front door. My issue is wasps. I imagine they are there for the black stuff that is on the tree. When the tree blooms, it gets worse. Makes it hard for deliveries?? Any advice on how to get rid of them and keep them away? You mentioned some stuff to pour at the base of the tree but what about something to spray on it also? I’d like to get ahead of all of that this year. I looked for a wasp nest last year but didn’t see anything. I admit, I didn’t try very hard…because of the wasps. Thanks in advance. ?

Allen's Answer: Hey Yvonne, Great question. I believe your problem with the wasps and the black stuff are related, and by getting rid of the sooty mold (black stuff) it will solve your wasp problem. Your Crape Myrtle, more than likely, has an infestation of Crape Myrtle Bark Scale, a small insect that attaches itself to the tree and sucks the fluid out of the tree. As it feeds on the plant, the scale secretes honeydew, a sticky substance that accumulates on the limbs and on anything under the tree. This honeydew ferments and turns black. The wasps, along with other insects, feed on the honeydew, thus attracting the wasp to the tree. So, controlling the bark scale should also keep the wasps away. Here are a couple of the more common methods that are used to control the scale. One is an application of a horticulture oil while your tree is dormant. This method is more labor intensive and requires spraying the tree completely, making sure to get the spray into the crevices at the limb junctions. The second method is to drench the soil with a systemic product that is mixed with water and poured around the base of the tree.  It will be absorbed by the roots of the tree and will move into the tree.  There are also Granular types.  This method is best applied as the tree begins to green up, usually around the first of April, and works for an entire year.  Examples of these products are Bayer Tree and Shrub Concentrate (Imidacloprid) and Ortho Tree and Shrub Insect Control Granules (Dinotefuran).  Always read and follow the label instructions of these products. Hope that helps - Allen 

To "Ask Allen" a question, email AskAllen@cityhs.net.  

Allen Bates is the City of Hot Springs urban forester, and he manages the City’s urban forestry care, preservation and health plan to provide the City with a safe, healthy environment for the City's urban forest.