Ask Dr. Hort: Prune hibiscus proportionately

Prune hibiscus proportionately

Q: When is a good time to trim back my hibiscus? How much is enough? Thanks. Roger, Seminole

A: Any time is good to prune hibiscus. When you prune, take enough off so as it grows back it will continue to flower. How much to prune depends on how large they are. If they are 6 to 8 feet tall, I would take off 2 feet. If they are 4 to 6 feet, I would take off 12 to 18 inches. If they are smaller than that, cut each branch back halfway.

Purple nutsedge a prolific problem

Q: Within our park there has been a grasslike weed that is everywhere. The weed is three to seven green blades with a single vein up the center of each blade. If not pulled, it will grow to about 18 inches and the blades widen. Eventually a cluster of seeds will form.

If you pull the plant straight up, it usually breaks off at ground level. If you pull it slowly toward you it comes up with what looks like a small nut at the base of the plant. As you continue to pull the plant, a root, running parallel to the ground, is found. Somewhere along this root another plant has formed.

Roundup or similar treatments barely yellow the leaves. A product such as Preen did nothing to remedy the problem.

What is the name of this weed? How can it be prevented or treated? Bob Gallion, Zephyrhills

A: It sounds like you, and many folks this year, have had a major problem with purple nutsedge (that's why you saw the little nutlike things), improperly named nut grass.

Sedges, even though they look like grasses, are in a totally different family. They are characterized by having very shiny leaves and a triangular-shaped seed stalk when cut in half and a cluster of seeds like sandspurs on the top.

Grasses, on the other hand, have hairy leaves (what makes you itch when you roll in the grass), round seed stalks when cut and seed heads with many branches.

Different herbicides are used to control sedges. Manage, Image and Basagran are good choices.

Japanese red maple needs cooler locale

Q: I purchased a Japanese red maple in May and transplanted it to a large pot that has drainage at the bottom. I put it in a spot that is under the shade of a large oak tree. It takes the morning sun and is shaded from about noon for the remainder of the day.

The problem is, the leaves keep turning brown. Over the summer I mostly just let the rain do the watering. The green part of the leaves remains subtle and I actually have new growth in a couple of spots. Is my girl sick? Thank you for your time and consideration in this matter. Kimberly Harwood

A: Your Japanese red maple, Acer palmatum, would do much better in Tallahassee. Its USDA hardiness zone of growth is zones 5 through 8. We are in zones 9 and 10 in our area. It is simply the wrong plant in the wrong place. Shame on the folks who sold you a plant that won't grow here.

Invasive weed has pretty blue flowers

Q: We have had a plant that seems to have taken over the yards in our neighborhood (around Britton Plaza in Tampa, just north of Gandy Boulevard and east of Himes Avenue). Some of our neighbors' yards have been almost covered with it. It has even overtaken the St. Augustine. Is this a good ground cover plant? Connie Brasier

A: The plant in question is dayflower, also called Asian dayflower. It grows from Florida to Canada, acting as an annual in colder climates and as a perennial here. In most places it is considered an invasive, noxious weed, however, it does have a beautiful blue flower. It likes to get started in shady, wet areas and can then cover quite an expanse. It will die back in winter and then go gangbusters through our rainy summer months. It can be controlled with the herbicide Speedzone, or Roundup plus Image for sedges. It resists most herbicides and is difficult to rake out because it roots at every node. Or you can keep it contained with herbicides and enjoy the blue flowers.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Need help?

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. E-mail him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: Prune hibiscus proportionately 12/24/10 [Last modified: Wednesday, December 29, 2010 10:30am]

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