Question and Answer – September 2011

If you’d like Neil’s help with a plant question, send it to him here. Neil requires that each question be accompanied by a photograph since e-gardens is a visual medium. Also, plant ID questions are usually not of general reader interest, so he suggests you take those to an independent retail garden center. Those are just about the only limitations. Click here to send your photo and question. Here are this month’s posts:

Question: I have this palm type of plant that seems to be withering somewhat. I repotted it, and that seemed to help, but it’s still not doing well. What else might I do? J.A., Monahans.

Answer: This is Dracaena marginata, sometimes called "dragon tree." Most dracaenas thrive in indoor lighting, but this popular one does not. It needs considerably more light than an average room setting would allow. It would grow famously for you near a south window or beneath a large skylight, as long as the room was bright by all other measures. It can be grown in very bright shade outdoors all summer, then put in a bright spot indoors over the winter. This wilted look is its direct response to inadequate lighting. Scheffleras and rubber plants do about the same thing – their leaves cup and roll. Light is your solution.

 

Question: I bought a Hick’s yew for my patio back in February. It did very well, until the past several weeks. It’s begun a fast downslide. When I pull the branches apart, I can see that the leaves are browned and ready to drop. I don’t see any insects on it, so I don’t know where to turn. Any idea what’s wrong? L.D., Plano.

Answer: Thirty years ago, I tried Hick’s yew and other Taxus species in my Collin County, Texas, landscape. I’d grown them for my few years of living in Ohio, and I was curious how they would perform in Texas. I had exactly the same outcome you’re having – no go. While there may be one or two species that can endure some degree of a Texas summer, a record-setter like this one is going to be their ultimate challenge. They can’t cope with the extreme temperatures over such a prolonged time. It’s not just about watering them. It’s that they can’t pull water through fast enough to meet the plants’ needs when it’s so hot. False Japanese yew (Podocarpus) would be a better option for you in Plano, but it’s a little touchy on winter weather and watering.

Question: These aralias have been in this location for many years. They are in full shade, and they receive regular watering. This year, they are dying, as are several others in my yard that were also established well. Friends tell me they’re having the same problems. Is this from the extreme heat, or is there another problem associated with them? L.M., Carrollton.

Answer: It’s definitely weather-related. Most fatsias/aralias in North Texas were eliminated by the extreme cold last winter. It may be that much of what you’re seeing is latent cold injury. The plants may be trying to send out new growth around that damage. Drought is also a possibility, but heat alone should not have done this. This species is almost tropical. If aralias are in the shade, and if they’re kept moist at all times, I’ve never seen them fail due only to heat.

Question: This bermuda lawn looked very healthy until recently. I have a sprinkler system and a smart controller. I’m mowing this grass a little high, because I have St. Augustine elsewhere, and it’s too much work to adjust mowing heights all the time. What would cause this? S.A.S., Dallas area.

Answer: This is an unusual splattering of die-out. I would suspect the disease organism Pythium, which is sometimes called cottony blight. We’ve had several similar photos posted here and on my Facebook page this summer, and a very reliable plant pathologist looked at a couple of them before pronouncing Pythium as the most likely candidate. It is a disease that shows up in summer, usually in the areas with wetter soils. (I note the drain.) It begins as a greasy, olive green patch of grass that fairly quickly turns this color. Turf fungicides will help, but I’d really suggest you send a sample to the Plant Disease Diagnostic Laboratory at Texas A&M. Collect several samples, and package them in separate bags. They should be from the interface of healthy and dead grass, and they should be showing active decline, not just dead grass. I would also include a couple of photo prints of the yard. There is a modest fee for their diagnosis. You can get all the information from their website, http://plantclinic.tamu.edu. Although you will have collected several pieces of the bermuda and packaged them into separate sandwich bags, send them in the same mailing box. You should only be charged for one sample test.

Question: I’m baffled why my bermuda is either dead or dormant in large areas of my lawn, while other areas are still green. I water about the same over the grass areas using traveling sprinklers. I fertilized in the spring. Our property is on a ridge, and the soil is somewhat thin and rocky. I assume the problem is some combination of water and soil conditions? J.W., Aledo.

Answer: You’ve diagnosed your own problem exactly. Traveling sprinklers are cool. They still intrigue me, just like they did when I was a kid. However, areas that are shallow and rocky won’t get enough water due to their limited storage capacity, and my bet is that the browning grass would almost serve as a topographic map for the rocky ridges beneath. It might make for an interesting quick test with a soil probe. The solution, when you have shallow soils, is to water more often, but to apply less at a time. Hopefully fall will turn things around. With some rains and one last feeding for the year, the turf should rebound fairly well. By the way, I do see the bermuda thinning in the shaded area beneath your tree. That’s strictly due to lack of sunlight.

Question: My problem is my dying Elaeagnus ebbengei plants. We have about 35 plants that were set out from 3-gallon pots three years ago. They are atop a small berm. We water them once a month in the summer, letting water drip slowly from a hose for 30 minutes. Various plants have died in random locations. The replacement plants are still doing well, although some of them are appearing wilted. We wondered about cotton root rot, since the plants died so quickly and the leaves remained attached. Any suggestions? P.P., Retta (between Mansfield and Burleson).

Answer: Cotton root rot would not be random. It would attack one plant, then the two that were adjacent to it. Plus, these plants are too far apart to be spreading it. That doesn’t matter anyway, because these plants have just gotten way too dry. At the temperatures we’ve had this summer, the monthly waterings you were making should actually have been on 5- or 7-day intervals. While elaeagnus plants are drought-resistant, they still need water, especially for the first several years as they’re getting established. I’ve seen hundreds of elaeagnus plants that looked just like yours, and drought has been the cause of every one of their deaths. I’d really suggest a quality drip irrigation line for watering these plants, and I’d suggest running it a couple of times a week until they’re well established.

Question: I planted several Harbour Belle, Gulfstream and Firestorm nandinas at my house and church last December. They look terrible now. Is this just due to the heat? I thought they were supposed to be tough. R.K., San Angelo.

Answer: Nandinas are tough for the most part. However, this summer has been one for the record books. Look at all the similar questions posted here this month on all kinds of durable plants, even bermudagrass included. This is heat and drought and nothing more. The plants may come back, or you may have to replace them in October or November. You’ll know by then. However, your original choice of varieties was good – and still is.

 

Question: What are these mystery cocoons? They’re everywhere. Friend or foe? C., Nevada, TX.

Answer: Those are all-American bagworms (not to be confused with webworms that attack pecans, mulberries and persimmons). Bagworms show up in late May and June, and they strip the foliage off junipers, redcedars, bald cypress, Leyland cypress, Italian cypress and arborvitae, among others. They’re very damaging. Time to watch for them (and to treat if you see them) is late May and early June. The young bagworms will be the size of a pencil point. They’ll be feeding actively, and they’ll be pulling the small bags behind them. Sevin, Malathion, B.t. or other general-purpose insecticides will eliminate them easily at that point. Now that they are through feeding, all you can do is to remove them by hand.

Question: I have been unhappy with the Indian hawthorns selected by our landscaper in 2001 (new home). Part of it is diseased, and part has frozen out. The beds go pretty much around the entire house. We have sandy soil, and it’s all mostly shaded. I water with a drip irrigation system. What plants would do well? C.P., Keller.

Answer: Lovely setting and home. I see a few of the plants I would recommend as replacements for the Indian hawthorns already growing in your landscape. The beds are fairly narrow. Dwarf hollies (Carissa, dwarf yaupon, dwarf Burford and dwarf Chinese) would be superior in either sun or shade, and all will stay small enough to fit your needs. Taller liriope would be a nice in-between plant in height and texture, and it would fit the boundaries. I’ve used Harbour Dwarf and Harbour Belle nandinas in compact spaces, even in shaded areas, just because they’re small and I like their textures. You could leave a few areas open from shrubs and put attractive decorative pots (16- to 20-inch) within the beds, then fill them with Dragon Wing begonias, wax begonias, impatiens, caladiums or other shade color. In fact, a grouping of three different-sized, white ceramic pots in the triangular bed at your walk might be attractive, and it would tie them to the pots you used elsewhere, just to maintain continuity. Random ideas. Hope they’re of some help.

Question: What is wrong with my Needlepoint hollies? They’re growing in mostly shade beneath large, old cherry laurels. I wanted them to grow large and conceal a fence, in case the cherry laurels end up dying. They’re scrawny, which I assumed was due to the shade, but is this probably also shade-related? S.T., Fort Worth.

Answer: I really do want you to send a twig-and-leaves sample to the Plant Disease Diagnostic Laboratory at Texas A&M. Click here to go to their website. Let’s be sure this is not a pathogen. I do wonder about leaf miners, as evidenced by the crescent-shaped hole in the left middle of your photo. These are tiny insects that tunnel around within leaf tissues before emerging and flying away. If leaf miners were involved, I would have expected more exit holes and holes in the lower leaves. All I see is the speckling. Systemic insecticides are the best long-term controls for leaf miners, should they prove to be the issue. You might do a more thorough analysis before you decide to send samples to College Station.

Question: What can I do to minimize salt damage done to my vitex by the neighbors’ draining their saltwater pool across my landscape? It has stunted its growth. L.F., Denton.

Answer: The way you minimize mineral salt damage to plant roots is to keep the salts diluted. Irrigate regularly with water that you know is not highly saline (no high content of sodium). You’ll keep the salt diluted, plus you’ll leach what is there down and out of the soil. Hopefully, the salt didn’t kill major parts of the vitex’s root system. It should look better by spring. Or, at least you’ll know where you stand.

Question: We live on three acres with hundreds of post oak trees. We’ve noticed borer holes in many of their trunks. The trees appear completely healthy otherwise. Do borers invade post oaks during droughts? Do we need to treat them, and if so, with what? Will it be wildly expensive? T. and E. H., Gainesville.

Answer: These holes may be from borers. You can determine that easily enough simply by opening up a large and fairly supple paper clip. Push it into a couple of the holes. If there are tunnels, they’re from borers. Borers seldom invade oaks out of the blue. Usually, it would just be one or two trees out of a forest, and usually only when those trees begin to age and decline. You probably don’t have anything to worry about, but it would be really prudent for you to get a certified arborist on site to look at the trees personally. Their consulting fee, just to establish what the true problem (if any) might be, would be a bargain worth investing in. Then you can make your decisions as to what to do next.