Weed With Black Seeds

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Broadleaf and blackseed plantain Plantago major L. and P. rugelii Have you found Black Medic in your lawn? Learn more about how to identify this weed, what conditions cause it and the best ways to remove and prevent it in the future. Bahiagrass (Paspalum notatum), also known as highwaygrass, is an aggressive, warm-season perennial grass. Bahiagrass has a mat-forming habit with a light…

Blackseed and broadleaf plantain

Family: Plantaginaceae (Plantain family)
Life cycle: Perennial, reproducing by seed
Native status: Broadleaf plantain is introduced to N. America, whereas blackseed plantain is native
Habitat: Turf, landscapes, waste areas

General description: Basal rosette of smooth, elliptic to oval leaves, up to 7 in long and 4 in wide. Leaves have prominent veins and usually inconspicuous hairs. As leaves mature the margins tend to get wavy. Flowers are inconspicuous, produced on a leafless stalk up to 10 in long. Flowers arranged in a spike that covers at least ¾ of the stalk. Has a fibrous root system.

Key ID traits: Rosette of oval leaves with prominent veins.

Similar species: Blackseed plantain can be difficult to differentiate from broadleaf plantain. Blackseed plantain usually has a red tinge at the base of leaf petioles and lacks hairs on leaf blades. Blackseed plantain has dull, black seeds whereas those of broadleaf are shiny and light to dark brown.

Miscellaneous: The plantains once were much more problematic as lawn weeds. They are much more susceptible to the growth regulator herbicides that are commonly used on lawns than many other perennial weeds. One reason for their greater sensitivity to herbicides than dandelion is the plantains have a fibrous root system rather than a taproot found on dandelions. The taproot stores more energy reserves than a fibrous root system, increasing the ability to come back from herbicide treatments.

Oval leaves with long, flat petioles characteristic of plantain. The red base of petiole suggests this is blackseed plantain.

Seedheads of broadleaf (left) and buckhorn (right) plantain

Successful weeds adapt to stresses in the environment. This plantain is able to survive a mowing height of 0.5″ or less in a creeping bentgrass golf fairway.

Black Medic

Black Medic, also known as Medicago lupulina or Yellow Trefoil, is a Summer annual weed. This means that it germinates sometime in the late Spring, grows well during the heat of Summer, then dies off with the cold weather. Black Medic is sometimes referred to as Yellow Clover because it looks like Clover with teardrop-shaped leaves, but has a yellow flower. The seed pods of Black Medic are also unique. They turn black when they’re ready to drop. If you can remove the Black Medic before this happens, it will help eradicate the plant, as the seeds are its only way of reproducing and they can stay viable for years and throughout Winter.

What Causes Black Medic?

It’s important to understand the conditions needed for Black Medic to thrive. A little Black Medic is normal. It will fill in the bare areas during the heat of Summer. A lot of Black Medic however, typically indicates that your lawn is being mowed too short in the Spring and Summer, your grass types are not strong or healthy enough to compete with the weed or your soil is compacted. If you notice the Black Medic growing by the roadside or next to a sidewalk, this is a sign that your soil quality is compromised due to foot traffic and compaction is the underlying problem.

How To Get Rid Of Black Medic?

Since Black Medic has a short lifespan, the bulk of your effort should go towards improving your lawn to prevent this weed from populating the following year. But there are a few things you can do to eliminate the weed right away.

  1. Pick the Black Medic. If you’re able to do this when the soil is wet, that would be ideal, as the roots will more easily and cleanly pull out of the ground. Black Medic grows out of a central location, so hand weeding can be very effective for removing the weed from large areas.
  2. Another option for elimination is to use a natural weed suppressant, such as Weed Beater Fe, which will be successful in killing the weed, however it also causes stress on the surrounding grasses, so use it sparingly.

How To Prevent Black Medic?

Black Medic and other annual weeds will emerge where your lawn is not competing. It could be that you’re mowing your lawn too short, which is keeping your grasses from growing stronger than your weeds. It could also be that the grasses you have are too weak and old and just don’t fight that well. Another option is that you have dry, compacted soil. Luckily, there are several ways to address the issues that could be resulting in the Black Medic in your lawn.

See also  Butterfly Weed Seeds

Mowing Problems

  1. One of the worst things you can do for your lawn is remove too much of the grass blade in a single mowing. Removing more than 1/3 of the grass blade length in a single mowing will turn the grass brown, stop root growth, and invite in weeds. So set your mower blades high.
  2. Dull mower blades are another common mowing issue because they rip the grass, instead of cutting it. This leaves your lawn vulnerable to disease and weeds and also dehydrates the grass blades, causing them to turn brown. A hardware store should be able to sharpen your blades for you. Try to do this every 20 hours worth of cutting or at least once per season

Grass Problems

  1. If you have older poor grasses, a total Lawn Renovation might be the best choice.
  2. If you don’t want to go that far, simply Slice Seeding your current lawn should make a big difference.

Soil Problems

  1. Given that compacted soil is an ideal environment for Black Medic to grow, we recommend aerating your soil. You can do Core Aeration or Liquid Aeration. If you’d like a DIY solution for aeration, try Liquid Aerator on the areas where you’re noticing the problem.
  2. Lastly you can try our Organic Soil Builder application, which will add valuable organic matter and nutrients to your soil, serving as an organic fertilizer that will promote healthy and balanced grass growth.

Contact us to learn more or to get our opinion on what would be best for your specific situation.

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.

Herbicide Bermudagrass Centipedegrass St. Augustinegrass Tall Fescue Zoysiagrass
sethoxydim NR S NR NR NR
imazaquin S-I I I NR S
metsulfuron S S S-I NR S
atrazine D S S NR NR
S= Safe at labeled rates.
I= Intermediate safety, use at reduced rates. Temporary yellowing of the turfgrass may occur.
NR= Not Registered for use on and/or damages this turfgrass.
D= Dormant. However, with the mild winters of recent years, bermudagrass lawns may not become completely dormant.

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
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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.

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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

If this document didn’t answer your questions, please contact HGIC at [email protected] or 1-888-656-9988.

Original Author(s)

Millie Davenport, Director of Home and Garden Information Center, Horticulture Program Team, Clemson University

Revisions by:

Joey Williamson, PhD, HGIC Horticulture Extension Agent, Clemson University

This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.

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