Sunday, June 17, 2018
Home and Garden

Ask Dr. Hort: Doing battle with creeping Bermuda grass

What's the best way to battle Bermuda grass?

Q: I have Bermuda creeping from my neighbor's yard into my St. Augustine. Any ideas of how to get rid of it?

Russell Vinson

A: Getting rid of your neighbor would be an easier task! Unfortunately, you can't kill a perennial grass out of a perennial grass with an herbicide, in your case, Bermuda grass, out of St. Augustine grass.

Another hassle with Bermuda grass is that it travels both by stolons (runners above ground) and rhizomes (runners underground). You could spray a 4- to 6-inch strip monthly with glyphosate (Eraser, Gly Pho-Sel, Ranger, Roundup) to keep the Bermuda grass stolons from encroaching, but still some rhizomes will make it under. You will achieve about 80 percent control this way, but make sure the stripe is on your side of the lot line to prevent a feud!

You can also use cypress, plastic, steel, aluminum or concrete edging, but that sets up a maintenance issue on both sides of the edging.

The best idea of all would be to eliminate the turf along that edge and create a nice planter bed with trees, palms, shrubs and ground covers with mulch and use the glyphosate whenever any Bermuda grass raises its ugly head.

Wiping out whitefly

Q: I have a black mold on the leaves of both my gardenias and crape myrtles. There are also tiny white flies on the underside of the leaves. Any suggestions?

Sheila Highsmith

A: You have identified your problem: whitefly! Whitefly is actually a scale, and if you look closely at the undersides of the leaves you'll see small, whitish to clear dots about 1/16 inch in diameter. In this larval (baby) form they suck plant juices and excrete honeydew, a clear sugary substance that ants and the sooty mold fungus in turn feed on. It is this fungus that blackens the leaves.

Purchase some 70 percent neem oil at your local garden center, or better yet, 100 percent neem oil online at neemtree Spray your gardenia, Gardenia angusta, every two weeks for three applications, following the label directions for rates, and make sure to cover the entire plant, especially the leaf undersides. This strategy will control the whitefly and flake off the sooty mold.

Don't worry so much about the crape myrtle, Lagerstroemia indica perhaps one application, because it will lose its leaves in a couple of months — but be vigilant when the leaves return in spring. It would also be a good idea to fertilize your plants because most pests, including whitefly, like to attack stressed plants either do to poor nutrition or insufficient irrigation.

The century plant's cycle

Q: I have a large cactuslike plant I planted under my palm tree a few years ago when it was about 6 inches tall. I never dreamed it would grow so large and have been removing "pups" to try to contain its growth since it seems to be too close to the palm tree now. It is pest-, drought- and cold-tolerant. A month ago, within just a couple of weeks, this very tall pole grew out of the center of the plant. The pole has a few small branches coming off of it. What is happening? What is this plant? Is it now too close to the palm tree? Should I cut it down and just leave a few small pups? What would you do?

Theresa Beckie, Riverview

A: The picture of your alien plant is called a century plant, Agave americana. There are numerous species, most notably Agave tequilana, the source of tequila. Agaves grow with the rosette of leaves with a thorn at the tip and, with many varieties, thorns down the leaf margins.

As it matures it flowers, which is what you are watching. The flower stalk will grow vertically — up to a 15- to 20-foot branch, flower and grow baby plants on the branches. As this occurs, the mother plant will die and the flower stalk will fall down, scattering the pups. The plant grows, flowers and then dies, hence its name century plant. However, all of this takes place, depending on species, in 5 to 15 years, much less than a century.