Boxwood blight a European import
Q: Why would my boxwood be dying at the tops of the plants? I have it all over my landscape. Is this too much or too little water?
A: A comparatively new disease has come from Europe to the East Coast of the United States in the past 15 to 20 years. Boxwood blight is affecting this genus exactly like your photograph shows. Google some of the major East Coast universities such as Clemson, North Carolina State and the University of Virginia to search for “boxwood blight,” and I think you will find good information on this relatively new disease.
You might also want to have a sample run through the Texas Plant Clinic at Texas A&M University. Its sampling and mailing instructions are available online.
I think there also is a chance that this is just dry soil. I see the dwarf nandina near the top of your photo showing similar symptoms, and boxwood blight would certainly not affect it.
Q: Unusual and hard growths emerge from our St. Augustine lawn. They look somewhat like mushrooms, but they are woody and heavy when dug up with a shovel. There was a tree in this vicinity years ago. What are they, and what should we do to prevent them?
A: These are saprophytic fungal growths, probably fungal conks that are existing off the decaying organic matter of the old tree roots. You could apply dusting sulfur over them to try to kill them, but avoid getting it all over the grass as it can burn foliage. It is also very irritating to skin and eyes.
I don’t know if you could dig down with a sharpshooter spade and remove the root without doing much damage to the turf. If that were possible, it might give the quickest relief. I notice the darker green grass within the circle of growths. That’s typical when these funguses release nitrogen they have been using as their food source.
Q: I have a bed of hardy hibiscus that became infested with mealybugs last year. I tried various organic controls to no avail. I finally turned to a harsh systemic insecticide. What do I need to expect next season?
A: Get rid of every piece of leaf and stem rubble now that they have (or soon will have) died to the ground following the first hard freeze. Blow the ground to get loose debris out of the way as well, then apply a fresh layer of mulch beneath them.
The mealybugs will probably not be an issue next season. Texas A&M says that soaps and oil sprays work to some degree, but primarily on the surface insects. The systemic insecticide Imidacloprid gives best results. Since it’s applied as a soil drench right around the base of each plant, its impact is minimized. That would be my recommendation should you see them again this year.
Q: Something is eating the leaves of my Nellie R. Stevens holly. What is causing it, and what should I do?
A:
That is very old damage, probably from last summer. My guess would be that it was either a voracious caterpillar or a fastmoving grasshopper. In either case, it’s long gone by now.
Those old leaves will soon be replaced by new growth in the spring. There is absolutely nothing to be done now.
Q: We moved into a new subdivision a year ago. A new live oak had been planted right before we took possession of the house. We thought it had survived the cold spell, but it began to develop some vertical splits in the trunk. It continued to grow well, but as fall approached some of the leaves began to turn yellow and fall easily. What should we be doing now so that we won’t have to start over with a new tree?
A: If the splits in the trunk didn’t get any worse over the course of the summer and fall, your tree will probably be fine. Without a photograph, I really can’t predict.
My best advice is just wait and see how it looks in April and May. If it leafs out normally and grows vigorously, then you should be fine. If it stalls or dies back, then you need to consider whether you want to replace it.
Q: Our downtown area includes a courthouse square with a sidewalk on all four sides bounded with flower beds. There have been live oaks there, but they have grown far too large. Their branches have grown into the side of the building. They also shed acorns everywhere. Our community is trying to decide which tree would be best to replace the live oaks. We need a selection that will not grow too wide and encroach on the buildings again. What would you plant?
A: I really would suggest that you work with a registered landscape architect who is also wellversed in local plants. One of the dwarf southern magnolia varieties might be ideal. So could a large tree-form holly.
So much of it depends on the architecture of the buildings and other plantings around the square. The landscape architect would have the experience of incorporating all those concepts into the final plan. It’s impossible to do a design without seeing the actual setting, either with a photograph or, better yet, in person.