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Gardening tips for weeds in the landscape

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By Staff Brunswick Beacon

Wherever I look in landscapes and turf, I see winter annual weeds going to seed. Now is a great time to assess the effectiveness (or lack thereof) of fall weed management programs. If henbit, speedwells, annual bluegrass and other winter annuals are plentiful in your beds, consider using a pre-emergence herbicide next August to prevent these pesky weeds from being as much of a nuisance next year.

According to Joe Neal, professor, Extension specialist and weed science specialist with N.C. Department of Horticultural Science, here are some tips for coping with weeds which are about to go to seed for next fall’ s crop:

Cutleaf Evening Primrose

I was just reminded many folks have trouble controlling cutleaf evening primrose in the spring. This winter annual weed can get pretty big and is hard to control at this time of year. Glyphosate does not work particularly well on this species. I’ve found glufosinate (Finale) works better but one application will still not provide complete control of those big, tough weeds. Again, it is best to control evening primrose with late summer applications of pre-emergence herbicides. I’ve found Gallery does not work that well on this species. Dinitroanaline herbicides such as Surflan, Pendulum, or Barricade have worked well.

Is it worth the time and expense killing the winter annuals now? After all, they are just going to die soon anyway? Well this is a question I get (and have asked myself at times). If you wait for the plants to die on their own, each plant will continue to produce thousands of seeds for next year. So, it is best to go ahead and kill these weeds. Even better, hand remove these weeds before they drop more seeds in your landscape.

Don’t forget, summer annual weeds are coming up already.

Wild Artichoke Woes

Florida betony, also known as wild artichoke or rattlesnake weed, is an aggressive, rhizomatous perennial in the mint family (Lamiaceae). Florida betony is actively growing now and when the summer heat arrives it will slowly disappear. Before that happens it will have developed a large underground white tuber which can be the size of a large carrot with ring segmented bands. It has square stems; leaves that are opposite each other and triangular in shape with toothed margins. Florida betony spreads primarily by rhizomes but viable seed are produced. Plants grow vigorously in the fall and spring then flower in mid- to late spring and die back to the ground during the summer. Although not a common weed of row crops, in landscapes it spreads rapidly and is very difficult to control.

This weed occurs in wet sandy soils, lawns, roadsides and thickets throughout Florida westward to Texas and north to Virginia. It is almost exclusively a weed of residential and commercial landscapes. However, naturalized infestations can be found throughout the southeastern coastal plain. Florida betony is rarely found in cultivated row crops suggesting that it does not tolerate conventional tillage.

Seedlings are rarely encountered. The most common means of spread is by rhizomes and tubers in soil moved with field-grown nursery stock and possibly in sod. This species is a category B noxious weed in North Carolina. Quarantine counties include Bladen, Brunswick, Cumberland, Forsyth, Hoke, New Hanover, Onslow and Wake (For more details see the NCDA Web site:

http://www.agr.state.nc.us/plantind/plant/weed/flbetony.htm).

Florida Betony Control

Sanitation is the best and most effective means of controlling Florida betony. Although it is rare to find Florida betony in nursery plants or sod, inspect balled and burlaped (B&B) ornamentals and sod (particularly centipedegrass and St. Augustinegrass) before planting. Refuse and return any plant materials found to have this weed in them. Rhizomes spread rapidly. Within one growing season a small infestation can enlarge to infest an entire landscape bed. Early detection and eradication is imperative. If Florida betony is found in a landscape, eradicate the weed as quickly as possible even if you have to kill some desirable plants in the process. When treating Florida betony infestations, it is imperative that the entire infestation be treated. In landscapes treat infested beds and the surrounding turf. Failure to do so will just perpetuate the weed problem.

In landscape beds the only selective herbicide that truly controls Florida betony is diclobenil (Casoron or Barrier). However, diclobenil will kill or severely damage any herbaceous ornamentals in the area, newly planted woody ornamentals and certain established plants including hemlock, fir, spruce, certain pines, and others. When using diclobenil, follow the label directions carefully; apply only in the winter (preferably December or January) around established, labeled ornamental species. Research has demonstrated that prodiamine (Barricade) applied in late Fall will stunt Florida betony, but the weed recovers by early summer. Glyphosate (Roundup, Roundup-Pro, and Glyphos) applied as a spot treatment or with a wiper have been somewhat effective, but repeated applications are necessary.

Most turfgrass infestations are in centipedegrass or St. Augustinegrass. Infestations in bermudagrass are much less common, and rare in cool-season turf grasses. Although Florida betony can tolerate mowing, frequent close mowing reduces its survival. Most post emergence broadleaf herbicides such as 2,4-D + MCPP + dicamba (Trimec, Weed-B-Gon, others) or clopyralid + triclopyr (Confront), do provide satisfactory Florida betony control. In centipedegrass, St. Augustinegrass, and bermudagrass turf, Florida betony may be controlled with atrazine (Aatrex and others) or a combination of bentazon + atrazine (a pre-mixed product sold under the trade name, Prompt). Apply in the fall to emerged Florida betony and follow with a second application in mid-winter or early spring. Do not apply products containing atrazine within the root zone of desirable ornamental plants or to cool-season turf grasses.

In either landscapes beds or turf, complete control will require at least two years of treatment. During these two years and thereafter, manually remove Florida betony plants whenever they emerge to prevent reestablishment. Try not to let the seeds set and fall to the ground to start new generations of this weed.