Q&A – Ask Neil: December 22, 2022
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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.
November 24, 2022 Q&A part one
November 24, 2022 Q&A part two
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QUESTION 1
SHOULD I REPLACE SKY PENCIL HOLLIES NOW?
Question: Several weeks ago you recommended against Sky Pencil hollies and said the retailers should stop stocking them. Prior to reading that I had planted two in my front yard. Are problems inevitable? Should I just dig them up and replace them? Fred N., Dallas.
Answer: Don’t dig them up until they become unsightly. Their problem is that they are not adapted to alkaline soils. The Dallas area has extremely alkaline soil and even more alkaline irrigation water, so my guess would be that it is only a matter of time. That’s why you see so few that look like anything after three or four years. But yours may be the exception. It just hurts me to see them sold and to see people buy them with hope and expectation. They are fine from East Texas eastward to the Atlantic Ocean, so I would certainly never expect the nursery industry to quit selling them. They just should not be promoted where they are not adapted.
QUESTION 2
WHEN SHOULD MINIATURE CRAPE MYRTLES BE CUT BACK?
Question: I have miniature crape myrtles, and I don’t know when to cut them back or how much. After the cold of 2021 they had to be cut back to the ground due to freeze damage. They came back the most beautiful ever. The plants are six years old. Karen G., Sherman.
Answer: In normal circumstances, I would recommend trimming them back by 50 percent in late January or early February. They are the least winter-hardy of all crape myrtles. As far north as you are, it would not be unusual to have to trim them back dramatically like you did.
QUESTION 3
WAS MY VITEX RUINED?
Question: A reputable tree trimming company offered to thin our vitex. I was so surprised to see the result. It looks like “crape murder” to me. Has it been ruined? Lauri L., Boerne.
Answer: I am so sorry for what they did to your plant. Thinning one out would be one thing, but cutting it back to nubs like this is awful. I looked at the “after” photo for several minutes, trying to figure if there would be a way to trim it additionally, to get rid of the whacked look. I couldn’t see one. If it were my plant, I might consider cutting it back to within a few inches of the ground and letting it regrow completely. Or I might go to the owner of the company and ask for a replacement. This plant is always going to show the scars of poor pruning.
QUESTION 4
WHY ARE THERE SO MANY COLORS IN OUR OAK TREES?
Question: I think we have both Shumard and red oak trees. Why do they have so many different colors in the fall? Bob O., Bedford.
Answer: There are many species of oaks across Texas, but Shumard red oaks predominate in DFW (including Bedford). Fall colors will typically vary from tree to tree and even on the same tree. You’ll even see a tree that was predominantly red one year show up as predominantly yellow or burgundy red the next year. It all has to do with the plants’ pigments, temperatures, rainfall and nutrients. The trees react differently to the same sets of conditions. This was an especially nice year.
QUESTION 5
HOW SHOULD I TRIM MY TEXAS A&M CENTURY OAK?
Question: This is a seedling from the TAMU Century Oak that I received for Christmas in 2019. It looks more like a shrub than a tree. How should I trim it and when? Steve S., Weatherford.
Answer: You want to do all pruning of oaks in the winter while they are dormant to lessen any chance of spreading oak wilt. Start with the bottom-most branches and remove one limb at a time. Step back and look at the tree carefully to see if you should take another one off. I can’t see enough detail in your photos to be able to guide you, but just do it gradually. Never cut more than 40 percent of the way up the trunk. Make each cut flush with the trunk. In other words, leave no stubs.
QUESTION 6
IS THIS GRUB WORM DAMAGE?
Question: I didn’t think bermudagrass was susceptible to damage of white grub worms. I took these photos in October. I watered carefully during the summer drought, but when I raked my lawn in early October whole sections came up. What would have caused it? Emil S., Collin/Denton.
Answer: Singly the worst case of grub worm damage I ever saw was a city block in North Dallas that averaged more than 65 grubs per square foot in early fall. It was all bermudagrass and you could have rolled up the entire block’s lawns like old carpet. But, to be sure, you have to dig a square foot of soil from the affected soil and look for white grub worms. The threshold of damage is 5 grubs per square foot. It’s too late to treat now. Keep your eye open next September and early October for the same type of damage. If you see it developing, dig to look for the grubs. If they’re there, apply Merit insecticide followed by a heavy soaking.
QUESTION 7
IS JANUARY PROPER TIME TO TRIM OAKS?
Question: I have been trimming my oaks in January on a freezing day. Is this the correct time to do it? Joyce G., Salado.
Answer: All oak pruning should be done while the oak wilt fungus is inactive. University plant pathologists and foresters tell us that the preferred time is between mid-July and mid-February. January is ideal, but you don’t have to do it while it’s freezing. Any day in January will be fine. Seal all cuts with pruning paint.
QUESTION 8
WHAT IS THE HARDINESS ZONE OF HAVARD AGAVE?
Question: I planted three Havard agaves in December 2020. We were told to cover them during the cold spells of 2021 and 2022. They survived perfectly. Now I’m reading that they’re winter-hardy. Which is it? Ramona S., Denton.
Answer: Plant Delights Nursery, one of the nation’s most respected plant sources, lists Havard agave (many people spell it “Harvard,” but as you can see, the species name has only one “r.”) Agave havardiana as being winter-hardy to Zone 5a. It will do fine in Denton. https://www.plantdelights.com/products/agave-havardiana