Bahiagrass

Bahiagrass (Paspalum notatum), also known as highwaygrass, is an aggressive, warm-season perennial grass. Bahiagrass has a mat-forming habit with a light green color, coarse texture, and open canopy. It is native to South America and was introduced into the U.S. in Florida as a forage grass around 1913.

Bahiagrass is easily identified by its distinctive “Y-shaped” seed head. It tolerates a wide range of soil conditions and spreads by seeds and rhizomes (a horizontal, modified stem found at or just below ground level). Bahiagrass growth is favored by drought, so it is an indicator plant for droughty soil conditions. The aggressive nature and drought tolerance of bahiagrass make it ideal for erosion control along roadsides and highway rights of way. However, its aggressive nature also makes it difficult to control as a weed in the landscape.

Bahiagrass habit with seed heads.
Ted Bodner, Southern Weed Science Society, Bugwood.org

Bahiagrass has distinctive “Y-shaped” seed heads.
Bert McCarty,©Clemson University

Before starting a weed control program, homeowners should realize that the complete eradication of bahiagrass (or any weed) from the landscape is not practical. A more practical approach is to control (not eradicate) the weed by limiting the infestation to a tolerable level.

Control in Lawns

Maintaining the health and density of your lawn is the best method for preventing a weed problem. Proper mowing height, irrigation, and fertilization of turfgrass will be the best defense against weeds. For more information on these topics, see the following fact sheets: HGIC 1201, Fertilizing Lawns; HGIC 1205, Mowing Lawns; and HGIC 1207, Watering Lawns.

If bahiagrass becomes a problem in a turf area, it can be dug up, or an herbicide may be used. If an herbicide treatment is chosen, treatments should be timed appropriately for optimum effectiveness.

Since bahiagrass is a perennial weed that also reproduces by rhizomes, post-emergent herbicides will also be necessary for improved control. Post-emergent herbicide applications should start in May when bahiagrass is small and starting to actively grow. See table for safe herbicides according to turf species.

Turf Tolerance to Post-emergence Herbicides for Bahiagrass Control.

Once bahiagrass weeds have been eliminated in areas of the turf, bare spots will be left behind. To prevent the invasion of new weeds in these bare spots, it is best to fill them with plugs or sprigs of the desired turfgrass.

Glyphosate: Non-selective herbicides, such as glyphosate, can be used for spot treatments; however, desirable grasses can be severely injured or killed with contact. Multiple applications of glyphosate will be required to control bahiagrass. Examples of glyphosate products in homeowner sizes are:

• Roundup Original
• Martin’s Eraser Systemic Weed & Grass Killer
• Tiger Brand Quick Kill Grass & Weed Killer
• Ultra Kill Weed & Grass Killer Concentrate
• Ace Concentrate Weed & Grass Killer
• Bonide Kleen-up Grass & Weed Killer
• Gordon’s Groundwork Concentrate 50% Super Weed & Grass Killer
• Monterey Remuda Full Strength 41% Glyphosate
• Hi-Yield Super Concentrate Killzall Weed & Grass Killer
• Southern States Grass & Weed Killer Concentrate
• Zep Enforcer Weed Defeat III
• Eliminator Weed & Grass Killer Super Concentrate

If it is not practical to prevent glyphosate from getting on desired grasses, then a selective herbicide should be used. The following information is a guideline for choosing a selective herbicide according to turfgrass type.

Atrazine: Atrazine is a post-emergence herbicide for bahiagrass control that also has pre-emergence activity to give fair control of bahiagrass seed. It will also give post-emergence control of many broadleaf weeds. However, it is only safe to use on centipedegrass and St. Augustinegrass lawns. For maximum effectiveness, apply atrazine when air temperatures reach 65-70 °F for four consecutive days. Examples of atrazine products in homeowner sizes are:

• Hi-Yield Atrazine Weed Killer Concentrate
• Southern Ag Atrazine St Augustine Weed Killer Concentrate

Sethoxydim: For centipedegrass lawns, the use of sethoxydim (BASF Segment II Herbicide)  will suppress bahiagrass. Sethoxydim should be applied no sooner than 3 weeks after centipedegrass spring green-up. Wait until lawns are fully greened. For a more effective bahiagrass treatment, do not mow 7 days before or after treating with sethoxydim. Reapply sethoxydim 3 weeks after initial application to suppress bahiagrass growth and seed head development. Do not make more than two applications per growing season.

Imazaquin: Image Kills Nutsedge is a homeowner-packaged, post-emergence herbicide product that will aid in the control of and reduce competition from bahiagrass. It may be applied to established bermudagrass, Zoysiagrass, centipedegrass, and St. Augustinegrass but do not apply to tall fescue. Do not apply imazaquin to St. Augustinegrass for other weed control during the winter. Do not apply imazaquin just prior to or during spring transition (green-up of the lawn). Do not use imazaquin in vegetable gardens, and do not use the grass clippings from treated lawns as mulch in landscape beds or around vegetables, fruit trees, or small fruit plants. A repeat application may be made for difficult to control weeds after 6 weeks.

Metsulfuron: Quali-Pro MSM Turf Herbicide, Quali-Pro Fahrenheit, and Blindside Herbicide are professional use herbicide products that will control bahiagrass, as well as many broadleaf weeds.

Metsulfuron can be used on bermudagrass, St. Augustinegrass, centipedegrass, and zoysiagrass. The Quali-Pro Fahrenheit also contains dicamba for broadleaf weed control. Blindside Herbicide also contains sulfentrazone for nutsedge control.

A non-ionic surfactant (such as Southern Ag Surfactant for Herbicides, Hi-Yield Spreader Sticker, or Bonide Turbo Spreader Sticker) is required at 2 teaspoons per gallon of spray mix for best control with the metsulfuron products above. Read the metsulfuron product label for more information. Some discoloration of turfgrass may occur after the application of metsulfuron, and increased yellowing and stunting of turfgrass may occur with the addition of the surfactant. A repeat application may be required in 4 to 6 weeks for best control of bahiagrass. Follow label directions for a reduced rate on centipedegrass.

Do not over-seed or re-sod for 8 weeks, or plant woody ornamentals in treated areas for one year after applying metsulfuron. Do not apply metsulfuron herbicides within two times the width of the drip line of desirable hardwood trees. Do not allow spray drift to contact desirable shrubs, and high temperatures at application may increase herbicide drift. Make metsulfuron applications when temperatures are below 85 °F. Allow one week between application of metsulfuron and other lawn pesticide products. Read the product label for other precautions for each turfgrass species.

Control in Vegetable Gardens

It is best to attempt to treat weeds before tilling the soil for a vegetable garden. Tilling can break up and spread weed seed and perennial grass rhizomes throughout the garden plot. Some methods used to remove weeds in the vegetable garden include hand pulling, mulch, and post-emergent herbicides.

Cultural Control: Hand pulling bahiagrass may be a practical choice for small garden plots. If hand pulling, be sure to work when the soil is moist so that the bahiagrass roots can easily be removed from the soil.

Organic mulch (such as pine needles, ground leaves, compost, old hay, or grass clippings) can be used in the garden to help suppress bahiagrass development. Before laying the mulch, apply a layer of 6 to 8 wet newspaper sheets to act as a weed barrier. The newspaper layer will prevent weed development by blocking light to the weeds underneath and prevent their growth. Best of all, the newspaper should decompose before next spring. To prevent low oxygen levels in the root zone, keep organic mulch levels at a maximum of 3-inches deep.  For more information on mulching the vegetable garden, see HGIC 1253, Controlling Weeds by Cultivating & Mulching.

Glyphosate: A post-emergent herbicide can be used to treat the garden plot before planting. Glyphosate can be applied to the garden plot 3 or more days prior to planting. Glyphosate is most effective when weeds are actively growing, so do not apply during extreme heat, cold, or drought conditions. Multiple applications of a 1.5 to 2.0% glyphosate solution may be necessary to control perennial weeds like bahiagrass. See product label for mixing directions. For examples of glyphosate products in homeowner sizes, please see the “Control in Lawns” section.

Sethoxydim: Some products containing sethoxydim may be applied within the vegetable garden after planting. These will control most grass weeds, in addition to bahiagrass. However, do not apply near sweet corn. Examples of products labeled for use within vegetable gardens are:

• Hi-Yield High Yield Postemergence Grass Herbicide
• Bonide Grass Beater Over-the-Top Grass Killer II Concentrate
• Ferti-lome Over-the-Top II Grass Killer Concentrate
• Monterey Grass Getter
• Poast Herbicide

Control in Landscape Beds

In landscape beds, bahiagrass can be hand dug or controlled with an herbicide. As mentioned previously, it is best to prevent the invasion of bahiagrass by maintaining ideal growing conditions and using a 3-inch mulch layer to block weed development. Bahiagrass is a perennial weed that can emerge from both seeds and rhizomes. Once bahiagrass has made its way into the landscape bed, an herbicide may be necessary if hand pulling is not practical.

Glyphosate: A non-selective herbicide, such as glyphosate, can be used for spot treatments around ornamental plants but should be used with caution. Do not allow glyphosate spray mist to contact ornamental foliage or stems, as severe injury will occur. A cardboard shield may be used to prevent glyphosate spray from drifting to nearby ornamentals. For examples of glyphosate products in homeowner sizes, please see the list above in the “Control in Lawns” section.

Sethoxydim: Sethoxydim is a selective herbicide that can be applied safely in landscape beds containing most landscape plants but check the product label for a listing of tolerant plant materials. Sethoxydim will only control grass weeds; however, do not allow sethoxydim to contact ornamental grasses. A 2.5% solution should be applied before bahiagrass reaches 4 inches tall. Read label directions for mixing. Examples of products containing sethoxydim in homeowner sizes are:

• Hi-Yield Grass Killer Postemergence Grass Herbicide
• Bonide Grass Beater Over-the-Top Grass Killer II Concentrate
• Ferti-lome Over-the-Top II Grass Killer Concentrate
• BASF Segment II Herbicide
• Monterey Grass Getter

Glyphosate and sethoxydim are both more effective when weeds are actively growing and will not work well for weed control under drought conditions. As with all pesticides, read and follow all label instructions and precautions.

CAUTION: Atrazine and imazaquin can travel through soil and enter groundwater; please read the label for all environmental precautions. Users are advised not to apply atrazine or imazaquin to sand or loamy sand soils where the water table (groundwater) is close to the surface and where these soils are very permeable, i.e., well-drained.

Pesticides are updated annually. Last updates were done on 7/22 by Barbara Smith.

Originally published 10/08