Mexican Petunia

Mexican petunia, or Ruellia simplex, spreads freely by its rhizomes as well as by seed dispersal. I can take over a landscape if you’re not careful.

Q. Dear Neil: The enclosed plant came into our yard beneath our backyard fence. It grows about 3 feet tall and I’m wondering how to stop its spread. What is it?

A. You now have Mexican petunia, Ruellia simplex. It’s a beautiful, strongly growing perennial that spreads freely by its rhizomes and also by its rampant distribution of seeds. It is even banned in some states entirely. That’s a shame, because it’s a lovely perennial that blooms freely in shady gardens. We haven’t reached those regulations on a statewide basis in Texas, but it does serve as a warning. You may want to stick with the more compact forms of Katie’s Dwarf, Bonita and Chi Chi instead.

Q. Dear Neil: We have a lot of 4-leafed clover in our lawn (the type with yellow flowers and short stems). I tried weed-and-feed, but it didn’t help. The big box store lady sold me a product, but it seemed to hurt my St. Augustine pretty badly. What will get rid of this weed?

A. You have sheep sorrel (oxalis). There are two main problems in controlling it. First, its leaves are very waxy. Any spray you apply to it beads up and rolls off. Use a broadleafed weedkiller (containing 2,4-D). I suggest putting one drop of liquid dishwashing detergent into each gallon of spray that you mix. Use a tank sprayer and apply it as a fairly fine droplet size so that you coat the leaves almost to the point of runoff. The more vigorously the weed is growing the better the control will be, so spring may be your best time. The second big issue is that oxalis seed capsules literally explode when they’re mature, dispelling seeds 5 or even 10 feet in all directions. Mow frequently to keep it from blooming and going to seed.

Q. Dear Neil: For the second time this year the impatiens I have in pots on my patio have died. I looked closely and found tiny webs. What causes this? I never had this problem in Spokane, Washington, when I grew them there.

A. You were seeing the webbing of spider mites. They’re the most damaging pests of many types of plants across the South. Having lived in the Midwest for seven years and visited Washington four times, both east and west ends of the state, I know that impatiens are used a great deal. But they struggle more with our Texas temperatures, and the nearly microscopic mites really tear into them. By the time the mites form webs it’s usually too late to save the plants. Look for the tan mottling of the leaves as the first evidence and use an insecticide labeled for control of mites on both top and bottom leaf surfaces. You can see the actual mites if you thump the declining leaves over a sheet of white paper (before you spray). The mites will be the ultra-tiny reddish specks that start moving.

Q. Dear Neil: I have seen, from my years of living here, that red tips do well for several years, then the leaves end up turning red and the plants die. Is there anything we can do to keep this great privacy plant from developing this problem, whatever it is?

A. Redtip photinias probably shouldn’t be described as “great.” This is Entomosporium fungal leaf spot, and it has caused redtips to become very poor landscape investments from coast to coast and all across the South. Unfortunately, no one has found a preventive measure, and no one has found a cure. Once the plants start to develop the maroon spots on their leaves, it’s a slippery slope to the finish line. And to make matters worse, Indian hawthorns, their closely related cousins, are now being ravaged by the very same disease.

Q. Dear Neil: I’m in the military and have just relocated to Texas recently. I now own my first fig tree. It was badly overgrown and leaning around a corner to reach sunlight. I have pruned the trees that were shading it, and I pruned the fig as well. Does it need to be pruned regularly? Does it need to be supported? I don’t know how to care for them. Thanks.

A. You’re thanking me? Oh, that’s backwards! Thank you! As for figs, in their ideal world, they would grow in a roomy location where they could mature at 15 or 18 feet wide and never have to be pruned. Two-thirds of the people reading this may just have fainted because they have figs up near their houses. So “Plan B” is to remove as little of the growth as you can get by with, and always to prune flush with other branches so that you don’t leave stubs. New growth will always be strongly vegetative, which means that it’s going to be reluctant to flower and produce fruit. Keep the plant moist at all times. Mulch it well and avoid high-nitrogen fertilizers, again to reduce the tendency toward strong vegetative growth.

Q. Dear Neil: I have a persimmon tree that is six years old. It has borne fruit, but I have never had any of them reach maturity. Most of the years they have dropped off as small fruit. Last year several reached full size, but just before they were ready to turn colors they were stripped off the tree, probably by a raccoon or opossum. What can I do?

A. Seedless persimmons are well known for aborting their fruit before it reaches full size. It’s imperative that you keep the tree uniformly moist all summer long. And you’re right about the animals stripping the fruit. You might figure out some type of trunk collar out of sheet metal that would keep them from climbing the trunks for their harvests. They’re really crafty, however. It’s difficult to outsmart them.

Have a question you’d like Neil to consider? Mail it to him in care of this newspaper or email him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.

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