Q&A – Ask Neil: March 13, 2025
(Please read these instructions carefully.)
Before you post your question, please look at recent issues to see if someone else has already asked it. You might find your answer there.
How to submit your question…
(Note: You may need to allow a pop-up window to come up in order to get the link for sending your photo(s). If you have already submitted your question and didn’t see the pop-up window, please click here.)
• Click the link provided below to post your question. After you submit your question, a new window will pop up giving you the address to which you can e-mail a SHARP, HIGH-RESOLUTION PHOTO to accompany your question. Please DO NOT SEND THUMBNAIL PHOTOS in case I need to zoom in to see things.
• Click here to post your question.
• Please ONLY POST YOUR QUESTION ONE TIME. We can only accept a set number of questions each week, and when we get duplicates it costs other people their chances.
• One question per reader, please.
• Please use this only for posting questions – not for standard emails.
• Watch for your answer in the following week’s e-gardens.
• I choose those of greatest general interest. For example, plant IDs seldom make the cut.
• I must have your first name or initials.
• I must have your city or county. (Texas is a very large state.)
QUESTION 1
SHOULD I FERTILIZE MY CRAPE MYRTLES?
Question: I have had crape myrtles in my landscape for more than 50 years. They have never been fertilized. Today I saw a crape myrtle fertilizer. They are standard types and are about 35 ft. tall. What do you think? Betty G., Glen Rose.
Answer: Without intending to, you have actually asked two closely related questions. (1) Do crape myrtles need to be fertilized? (2) Do they need a specialty food that’s been made just for them?
Crape myrtles bloom on their new growth each year. You have probably noticed that the tip few inches of each branch dies off and drops to the ground at the beginning of each growing season. New shoots develop around its old space, and they quickly start producing flower buds. The more new growth you get then and throughout the summer, the more rounds of new flowers you’ll get during the summer. I’ve seen plants bloom as many as four times if they
were fed with a high-nitrogen food at the beginning of spring and a couple more times during the summer.
As for whether that particular fertilizer would be “the one” for your plants, that would depend on its analysis. The first number (nitrogen) of its 3-number analysis of contents needs to be the highest. Even though phosphorus, middle number of the analysis, is the nutrient responsible for promoting production of flowers (and fruit and root growth), phosphorus tends to accumulate in most Texas soils, often to excessive levels. Nitrogen promotes that much needed new growth, hence is critical to production of new flowers as I mentioned. Try feeding them this year and see how it works out.
QUESTION 2
WHEN AND HOW DO I REPLANT MY ST. AUGUSTINE AREAS THAT DIED DUE TO TAKE ALL ROOT ROT?
Question: I have spots in my St. Augustine due to Take All Root Rot. When and how do I replant the grass there to make it look good going forward? Is there now a preventive treatment? Van R., Dallas.
Answer: Be certain it was TARR that killed your St. Augustine and not something else like excessive shade. You’d be amazed at how often people make that mistake. Planting new St. Augustine sod where shade caused the old grass to die is a total waste of money and effort unless you take steps to eliminate the shade by removing major branches or taking down trees.
Take All Root Rot, if it was indeed the cause of the loss of your grass, results in irregular patches that are yellowed in late March, April and early May. When yellowed runners are pulled, they come loose easily from the soil due to loss of roots. The infected roots are short and blackened due to the disease. Healthy, green turf may be visible just inches away. Application of the fungicide Azoxystrobin has been reported by university turf experts and plant pathologists to kill the disease, whereas our old remedy of spreading a 1-inch layer of sphagnum peat moss across the lawn merely suppressed it for a period of time. TARR is most common in alkaline soils near and west of I-45 and most especially along and west of I-35.
There is a great deal of research being conducted on disease resistance of various St. Augustine cultivars. Before you spent major dollars in the hopes of outrunning it in your landscape, I would suggest you do some thinking about how things died out last year, then some online research of the options available to you. The University of Florida has charts comparing the many varieties and their winter hardiness and disease resistances. I still don’t see any cultivar that is (a) winter hardy and (b) resistant to TARR.
QUESTION 3
WILL LEAVES COME BACK ON OUR MAGNOLIA TREE?
Question: Last summer grasshoppers ate everything, including the leaves on our 2-year-old southern magnolia tree. Will the leaves come back this spring? Gayle C., Burneyville, OK (southern part of the state).
Answer: I can’t tell, but you can. Scratch the trunk or a small branch with your thumbnail. If the tissues beneath the bark are still moist and green, it will leaf out again.
If it is, I would apply an all-nitrogen lawn fertilizer (no weedkiller included) around it and water it thoroughly. Follow the label directions for amount to apply carefully. You certainly don’t want too much. Probably less than ¼-inch over an area the size of a card table. You’ll know how vigorous it’s going to be within a few weeks.
QUESTION 4
IS LOSS OF THIS CHUNK OF BARK FROM A RED OAK TRUNK A DANGER TO ITS LIFE?
Question: Is the loss of this chunk of bark from our red oak’s trunk a threat to its life? Mary Ann D., Plano.
Answer: It’s certainly not normal. And it looks like the bark directly above the wound might also be loose and disturbed. It may come off as well. If you have a certified arborist who looks after your trees, I’d definitely have them check this one out. You’ll be able to tell more once the tree leafs out this spring. It’s possible that that side of the canopy will be thin due to decay in the trunk. This could have resulted from some kind of injury, sunscald, old rodent damage, or a variety of other causes. I’d like to be able to see where the root flare is just to be sure the tree isn’t planted too deeply. It does not look like normal bark sloughing due to trunk expansion through growth. It definitely merits attention.
QUESTION 5
CAN I REMOVE ABOUT 1 FT. OF HEIGHT FROM MY BOXWOODS?
Question: I’d like to take about 1 ft. of height off my Japanese boxwoods to improve the look from both inside and outside my house. Can I do that without stunting their growth? Sharon M., Grayson County.
Answer: That’s a lot to be removing, especially this late. Assuming that your photo is already a week old, there’s a chance that your plants have started producing new buds.
You would obviously be trimming them with a hedge pruner, probably gasoline or electric. I would suggest that you start out by removing just 3 or 4 inches for a short distance from one end. Let that be your preview. It won’t take too long to do the “rough cut.” If you don’t like the look, the plants will quickly fill in this spring. Or, if you decide to remove more, you could do a second trial prune to remove another 3 or 4 inches.
Point being: do the cut gradually to be sure you don’t denude the plants in the process. You’ll need to round off the outer edges once you finish the top work. Complete the job with a high-nitrogen, lawn-type fertilizer and a deep watering.
QUESTION 6
WHAT RATIO OF NITROGEN/PHOSPHORUS/POTASSIUM MUST I USE AND WHEN?
Question: What ratio of N-P-K fertilizer is good to apply in the spring and during the growing season? How do I know when my lawn needs a fertilizer and what type? Orlova G-O, Dallas.
Answer: If you happen to have a copy of Neil Sperry’s Lone Star Gardening (the book you see advertised here) all of that is explained in detail in Chapter 1 dealing with The Basics where I explain fertilizers and Chapter 2, the perpetual calendar. But I’ll give you a condensed version.
You are in Dallas, so that’s Blackland Prairie alkaline clay soil. A soil test from the Texas A&M soil testing lab is always your best way of knowing exactly what you will need and when, but you can pretty well know that it’s going to call for an all-nitrogen product containing 30 to 40 percent of that nitrogen in encapsulated or coated slow-release form. Your local independent retail garden center operator can show you the various choices.
As for timing, it would have helped if you had mentioned which turfgrass you have. In the Metroplex you would fertilize common bermuda in early April, again in early June, early August, and early October – same product each time.
If you have St. Augustine, same product applied mid-April, early June, and early September. Zoysia could follow the St. Augustine schedule. Buffalograss would be once per year in late May.
QUESTION 7
WHAT IS WRONG WITH MY TWO RED OAKS?
Question: What is wrong with my two red oaks? It looks like fungus on the fallen limbs and trunk. Is it serious? Kathy M., Waco.
Answer: The gray “moss” on the trunk is a colony of lichens. It’s a symbiotic growth of algae and funguses that nourish one another. You’ll also see them commonly on “moss-covered” boulders, an indication that they’re not sucking life out of their supports. They’ll generally be on the shaded sides of the trunks, usually on the north sides.
The little mushrooms are saprophytes. They are on the twigs because they died and have fallen off. They’re existing off the decaying organic matter, so they’re no cause for concern. Keep your tree properly watered and fed. Without seeing a more distant photo, that’s all I can tell you.