GARDENER'S MAILBAG: What should I do about my pyracantha?

By Neil Sperry
Special to the Herald Democrat

Dear Neil: My pyracantha was damaged badly by the February cold. I had the dead branches removed and there was substantial growth along the remaining limbs. However, some of that growth has started to die from the top down. As you can see, there is healthy growth from the base. Should I remove the large trunks and just start over?

Pyracantha dying back after recovering from cold

We had mild weather in late spring and early summer across much of Texas. What you saw with your pyracantha is not uncommon with many species following the cold spell. My recommendation would be that you wait until September to see how much additional die back there is. At that point you can determine what pruning might still be required. Last February’s event has caused results that none of us has ever seen before.

Dear Neil: I have lived around mimosa trees all of my life. I now live in the country and my mimosa tree absolutely will not bloom. Why would that be?

It’s always difficult to identify why something does not happen. It’s essentially proving the negative. In the case of mimosas, the most common causes of failure to flower would be if you are topping the tree in the winter (some people still do) or if it is failing to grow vigorously for one reason or another. It could be that it’s in too much shade. They must have full sunlight to do their best blooming. Or perhaps it has reached the end of its productive life in the landscape. They do play out after 30 or 35 years. Take photos of the tree to a Texas Certified Nursery Professional. Perhaps he or she will be able to identify some other key to its sluggish performance.

Dear Neil: Why would my roses die back, first turning yellow, then brown and then black before I have to cut them off? I’ve never had this problem in other states.

Rose rosette virus showing gradual dieback

I fear your plants might be infected with rose rosette virus, the fatal disease that has ruined roses in many parts of Texas. It’s actually an old virus first identified 80 or more years ago. Affected plants also develop ultra-strong “bull” canes that are two or three times the normal size and height. Many of the canes have huge numbers of thorns, and flowers fail to open properly. RRV is spread by a microscopic mite that floats on the wind. Unfortunately, we have no control for either the mite or the virus. Research scientists have been trying to find a work-around for us for more than five years. I am including a photo of RRV that I took a year or two ago to show you what it looks like as it takes a plant down.

Dear Neil: I have a trellis in a protected location. What are some plants with fragrant flowers that I might want to consider, both as vines for the trellis and flowers in my garden?

Assuming temperatures won’t drop too far below freezing, my first choice for the trellis would be star jasmine with its highly fragrant white blooms in the spring and sporadically throughout the year. Carolina jessamine is nice, and it’s also mannerly in growth. Sweet autumn clematis blooms in August with small, fragrant flowers, but it’s big vine that requires a large support. As far as shrubs go, gardenias, elaeagnus, sweet olive, banana shrub and loquats are all fabulous. All were hurt by last February’s cold, so ask questions of your favorite independent nursery owner before you plant them. Roses are good if you do not have the aforementioned rose rosette virus in your locale.

Dear Neil: What is this on my crape myrtle (the white growth on top of the black layer), and what should I use to control both of them?

Crape myrtle bark scale and sooty mold on topped plant

The white insects are crape myrtle bark scale. They’re a relatively new pest in the United States, first being observed in Richardson, Texas, in 2004. Like other types of scale insects, they suck sap out of the plants’ leaves and stems and secrete a sticky honeydew that they exude all over the leaves and bark. A sooty mold fungus grows in it, and that fungus quickly develops a black color. The same sooty mold appears on old cars and pavement when trees drip sap on them. The important thing to remember about bark scale and sooty mold is that they are mainly aesthetic. You can prevent them with a mid-May soil drench of Imidicloprid around the drip line of each crape myrtle. They actually do no permanent damage to the plant. Repeated topping of crape myrtles such as I see in the photo is far more harmful.

Dear Neil: I moved into a new house and have beautiful oak trees. However, one has lifted on one side and I can see roots. Can I save the tree?

I would think so. It depends on the type of oak, since some are more prone to leaning than others – live oaks, for example. It also would depend on whether the tree actually pulled up out of the soil or whether its roots have simply grown up and out of the soil on that side. That’s very common. Either have a certified arborist look at the tree on site or take really clear photos to a Texas Certified Nursery Professional for suggestions. I can’t do much more to help without seeing the tree.

Have a question you’d like Neil to consider? Mail it to him in care of this newspaper or e-mail him at Neil regrets that he cannot reply to questions individually.