GARDENER'S MAILBAG: What is going on with my Nellie R. Stevens?
Dear Neil: I planted this Nellie R. Stevens holly a few months ago. Recently the dark green leaves started turning yellow, then the lower leaves turned dark and died. I put fertilizer on it and the color improved. (See photo.) What is wrong?
I can guarantee you that your plant got too dry one or more times. That is the only thing that will give those symptoms. Sadly, I know that from first-hand experience. (I chuckled as I typed that because I have done the same thing more than once.) Hollies have very stiff leaves, and they do not wilt when they begin to get dry. That means that they don’t give us any highly visible symptoms of drought. My rule of thumb is to water new shrubs and trees every two or three days during the warm months. I use a garden hose, and I apply as much water as the container from which each plant was removed. For example, a 5-gallon plant would get 5 gallons of water two or three times weekly. Hopefully this plant is already budding out with new growth, and with a little luck it can be saved.
(And for the other reader who struggles with a neighbor’s redcedars sucking water from his Nellie R. Stevens’ root zones, yes, it might help to put a root barrier in place near your property line. Have the utility company mark any of their lines before you start digging your 18-inch-deep trench, however.)
Dear Neil: What is causing the variegation in my liriope to change to all-green leaves?
First things first… lovely job with the landscaping. Great flow and nice use of high-quality plants. My guess on the changeover to green would be that the variegated form is not a stable selection, and that the plants are reverting. You can almost see that happening. The foreground plant is still solid with variegation. The one to the right has almost no variegation, so it appears to have reverted to, or been overtaken by, solid green. And the one in the upper left of the three is in the process of transitioning. You can see that it has a combination of both types of leaves. At this point you could either replace them all with a new grouping, or you could wait it all out and let the green take over. The textural differences alone would be nice.
Dear Neil: I have an invasion of crabgrass in my St. Augustine. Can I do something about it now, or do I have to wait until late winter?
You should begin by making sure you truly have crabgrass. It’s very late in the growing season for someone to be asking about it. Plus, it is rather unusual for it to show up in a St. Augustine lawn. St. Augustine is by far the dominant grass and usually crowds it out. I wonder instead if you might have dallisgrass. It is a much more common problem in St. Augustine. If that is the case, you could spot-treat with a glyphosate spray now before frost. You would need to use a pump sprayer so that you could treat each clump precisely. Or you could wait until spring to treat. If you do indeed have crabgrass, you would wait to apply pre-emergent weedkiller granules next spring. I will have details on that at that time.
Dear Neil: I planted Japanese yews on an eastern exposure along our driveway. A couple look very weak, while one seems to be holding its own. Is this all the result of last February’s cold? Do these need to be replaced?
For a variety of reasons, I probably would replace them. Yes, the February cold spell hurt Japanese yews very badly across Texas. Your plants seem to be included in those numbers. Even the plant that looks fairly good should be more vigorous. My suspicion is that the morning sun may not treat them well against the brick wall. I would recommend a rather upright holly such as Oakland. Scarlet’s Peak yaupon holly, while uncommon and sometimes hard to find, would be lovely there. Sky Pencil holly would be fine in the acidic soils of East Texas. Columnar junipers have some serious disease problems, as do Italian cypress, so I can’t recommend them. (The cypresses also grow far too tall.) You might also consider an espalier or vine.
Dear Neil: Can this pecan tree be saved, or does it need to be taken down?
I don’t want to be the executioner of a pecan tree based solely on one closeup photo. You need to have a certified arborist look at this tree from all angles. He or she will also evaluate the top growth and how full the canopy is. However, on quick sight, I have to admit that this does not look good. It looks like a big part of the truck is involved and that the tree may be very weak. It looks like it could come down on its own at almost any time. Reach out for professional help before it starts losing most of its leaves. They are very important in analyzing its vigor.
Dear Neil: I’ve had these boxwoods for 10 years, but in the past year or two twigs and branches have started dying fairly rapidly. What could be causing this?
I can’t tell from your photograph. It could be the impact of nematodes. They’re microscopic soil-borne worms that suck plant “juices” and often cause knotty galls on the roots. And there is a new disease that has shown up on the East Coast. Boxwood blight has been brought into this country from Europe. I’ve written about it here fairly recently, so I won’t go into lengthy detail, but you can Google information from North Carolina State, Purdue and Clemson Universities as well as the Universities of Wisconsin and Maryland. The Texas A&M Plant Disease Clinic could run diagnostic tests on root and top-growth samples to determine the problem for you. There is a fee for their services. All is explained at their website.
Have a question you’d like Neil to consider? Mail it to him in care of this newspaper or e-mail him at email@example.com. Neil regrets that he cannot reply to questions individually.