Weed With Seeds Under Leaves

Chamberbitter: Invasive and Difficult to Control Chamberbitter ( Phyllanthus uri­naria ), also called gripeweed or leaf flower, is a highly inva­sive summer annual broadleaf that has become a Chamberbitter (Phyllanthus urinaria) is also known as gripeweed, leafflower, or little mimosa. It is a warm-season, annual, broadleaf weed that emerges… Does your lawn have chamberbitter taking over? Our DIY Chamberbitter control guide will show you how to get rid of this pesky weed quickly.

Chamberbitter: Invasive and Difficult to Control

Chamberbitter (Phyllanthus uri­naria), also called gripeweed or leaf flower, is a highly inva­sive summer annual broadleaf that has become a serious weed of nurseries and landscape beds in Louisiana over the past 15 years. It is believed that the weed orig­inated in tropical Asia, but it has become problematic across the southeastern United States from Virginia to Texas.

The weed is characterized by leaves arranged in two rows on alternate branchlets, superficially resembling mimosa seedlings. However, the most common distinguishing feature is fruit attached directly to the underneath sides of branches. Reproduction is by seeds, which explode outward from maturing fruit onto surrounding areas. Seeds require soil temperatures above 75 degrees to germinate, and plants persist into late fall until a killing frost. Chamberbitter grows 1 to 2 feet in height and produces thousands of seeds. The weed is unsightly in flower beds and is costly to control in nurseries.

Chamberbitter control in landscape beds and nurseries

Because few selective postemergence options are available for controlling broadleaves infesting ornamentals, preemergence herbicides are the back­bone of weed management in flower beds and nurseries. Unfortunately, chamberbitter responds erratical­ly to most preemergence herbicides labeled for ornamentals. However, a few preemergence herbicides pro­vide at least suppression of the weed. Herbicides that contain oxyfluorfen (Rout, OH2 and others), flumioxazin (Sure Guard and Broadstar) and isox­aben (Snapshot, Gallery) are useful in reducing chamberbitter populations in perennial groundcovers and woody plants. Dimethenamid-containing her­bicides (Free Hand and Tower) can be moderately effective in bedding plants. Always follow product labels and pre­cautions when using herbicides in and around ornamentals.

With all preemergence herbicides, it is important to apply them before weeds germinate.

Chamberbitter is a tropical plant that starts germinating as temperatures warm in the springtime, usually late April, so apply preemergence herbicides accord­ingly. Re-apply as directed by the prod­uct label. In landscape beds, a good thick mulch will also help suppress chamber­bitter emergence, especially when used in conjunction with an effective preemer­gence herbicide.

Since chamberbitter is a prolific seed producer, it is extremely important to not allow emerged plants to produce seed and add more seed to the soil weed seed bank. Either hand-remove the weed or apply a non-selective herbicide such as glyphosate to destroy populations before they have a chance to produce seeds.

Chamberbitter is an extremely dif­ficult weed to manage in ornamental settings. It will take an integrated man­agement approach that includes mulch and preemergence herbicides along with frequent hand weeding and glyphosate applications to reduce populations in nurseries and landscape beds.

Ron Strahan is a weed scientist and associate professor in the School of Plant, Environmental and Soil Sciences.

Fruit on chamberbitter. Photo by Ron Strahan

Chamberbitter seed capsules are located on the underside of leaves. Photo by Ron Strahan


Chamberbitter (Phyllanthus urinaria) is also known as gripeweed, leafflower, or little mimosa. It is a warm-season, annual, broadleaf weed that emerges from warm soils beginning in early summer. It reproduces by seeds, which are found in the green, warty-like fruit attached to the underside of each branchlet.

Chamberbitter grows upright and has a well-developed taproot. The leaves are arranged in two rows on the branchlets and are thin and oblong, with smooth margins, resembling a mimosa seedling.

Management of chamberbitter is best achieved through the integrated use of mechanical, cultural, and chemical methods.

Mechanical Control

Mechanical weed control involves the physical removal of the weed from the soil. This is best accomplished by hand when weeds are young and small or in the seedling stage and easier if the soil is moist. Preventing the weed from reaching maturity and setting seeds also reduces future weed populations.

Cultural Control

Cultural weed control is the prevention of weeds through proper lawn management practices. A properly mowed turf that is not stressed by insects, diseases, drought, or nutrient imbalance is the best defense against weeds. For more information on watering, fertilizing, and mowing, see the following fact sheets: HGIC 1201, Fertilizing Lawns, HGIC 1205, Mowing Lawns, and HGIC 1207, Watering Lawns.

Within landscape beds, apply two to three inches of mulch in the spring to cover seeds from the previous season. Because chamberbitter seeds require light to germinate, this is especially effective.

Chemical Control in Lawns

Preemergence Herbicides: Because preemergence herbicides prevent seedlings from developing, they are an effective tool against annual weeds. However, they will not affect established weeds. Timing is critical. They must be applied prior to seed germination.

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Atrazine is effective for preemergence control of chamberbitter in centipedegrass and in St. Augustinegrass lawns. Be careful not to apply on turf during the transition period from dormancy to active growth (spring green-up). Because chamberbitter tends to germinate in late spring and early summer (once the soil temperature reaches 70 °F), applications after grasses fully green up are effective. Target areas where chamberbitter was observed the previous season and be careful to not apply near the roots of desirable landscape plants. See Table 1 for examples of products.

Isoxaben is a preemergence herbicide that is effective for chamberbitter control in tall fescue, centipedegrass, St. Augustinegrass, bermudagrass, and zoysiagrass lawns. For home lawn use, it is purchased in a granular form, and the granules must be watered-in to allow the isoxaben to coat the soil surface for weed prevention. Make the first application in late spring and the second about 8 weeks later. See Table 1 for examples of products.

Isoxaben is also available as an additional active ingredient in one Bayer Advanced brand three-way herbicide. With this product, the postemergence, three-way, broadleaf weed control portion controls existing chamberbitter plants. The isoxaben portion will aid in preventing reinfestation of the area from seeds that may be present. To prevent new seeds from growing, the entire area to be protected must be sprayed. Wait 2 days after spray application and activate the isoxaben residual barrier by watering the lawn with ¼ to ½ inch of irrigation. Do not seed or overseed within 60 days after application. Do not apply isoxaben to a newly seeded lawn until it has been mowed 3 times. See Table 1 for an example of product.

Postemergence Herbicides: Postemergence herbicides are most effective when applied to young weeds. For postemergence control of chamberbitter in St. Augustinegrass and centipedegrass lawns, atrazine is recommended. It has both preemergence and postemergence properties. Make two applications spaced 30 days apart. Do not begin treatment with atrazine on these two turfgrasses until they are fully greened up in the spring.

On tall fescue, bermudagrass, and zoysiagrass lawns, repeat applications of three-way herbicides that contain 2,4-D, mecoprop (MCPP), and dicamba can be used to control chamberbitter. Apply these herbicides in late spring or early summer when the weeds are still young and space second application at 30 days later. These three-way herbicides may also be used on centipedegrass and St. Augustinegrass lawns at reduced rates and after the grasses have completely greened-up in the spring. Read the product labels for rates to mix and apply. See Table 1 for examples of products. For more information refer to HGIC 2310, Managing Weeds in Warm-Season Lawns.

Celsius WG Herbicide, which contains thiencarbazone, iodosulfuron, and dicamba, will control chamberbitter, especially if applied when the average daily temperatures are over 60° F. Apply when chamberbitter is actively growing and again 2 to 4 weeks later, if needed. The addition of a non-ionic surfactant, such as Southern Ag Surfactant for Herbicides, will increase control.

Control in Landscape Beds

Postemergence Herbicides: The best choice for controlling existing chamberbitter in landscape beds is one of the many products containing glyphosate. Glyphosate will move through the plant and into the roots to kill the entire plant. Buy a 41% glyphosate concentrate and follow label directions for mixing a 2% solution to spray in a pump-up sprayer. See Table 1 for examples of products.

Glyphosate is a non-selective herbicide which can potentially damage any plant through contact with foliage or bark. Protect desirable plants from drift by not spraying in windy conditions, by keeping the spray nozzle close to the ground, and by using low pressure. Further protection is provided by attaching a plastic, cone shaped shield that surrounds the spray nozzle and confines the spray to the targeted plants. Shields can be made from bottomless two- liter drink bottles. Plants can also be shielded by covering with cardboard or something similar that is disposable.

When herbicides are applied to beds intended for future planting of ornamentals, care must be taken as various herbicides may injure the plants to be installed. For planned beds, glyphosate has far less soil activity (a few days) as compared with the three-way herbicides (a few weeks). Glyphosate is the safest choice for spray application in existing flower and shrub beds, so long as care is taken to prevent drift to non-target plants. Glyphosate applications are much less apt to move through the soil, be absorbed by roots, and injure existing woody ornamental shrubs.

Preemergence Herbicides: Isoxaben can be applied as a preemergence herbicide in landscape beds around certain well-established ornamental shrubs and trees to prevent chamberbitter from growing from seed. Products are best put below the mulch layer. Do not apply preemergence herbicides in beds where new plants will be installed, as plant root development may be inhibited. See Table 1 for examples of products.

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Pesticide Safety

Always read the pesticide label and follow its directions exactly. Be sure to observe all precautions listed on the label. Mix pesticides at the rate recommended and never use more than the label says. Wear protective clothing or equipment as required by the label when mixing or applying pesticides. You may use the pesticide only on sites or crops listed on the label. Follow all label directions for pesticide storage and disposal.

Always heed the six most important words on the label: “Keep out of reach of children.”

Table 1. Examples of Herbicides for Chamberbitter Control in Turfgrass & Landscape Beds.

Roundup Original Concentrate

Roundup Pro Herbicide
Martin’s Eraser Systemic

Weed & Grass Killer
Hi-Yield Super Concentrate

Killzall Weed & Grass Killer

Bonide Kleenup Grass & Weed Killer Concentrate; & RTU 2

Eliminator Weed & Grass Killer Super Concentrate

Gordon’s Groundwork
Concentrate 50% Super Weed & Grass Killer

Knockout Weed & Grass Killer Super Concentrate

Monterey Remuda Full Strength 41% Glyphosate

Quick Kill Grass & Weed Killer

Southern States Grass & Weed Killer Concentrate II

Tiger Brand Quick Kill

Total Kill Pro Weed & Grass Killer Herbicide

Ultra Kill Weed & Grass Killer Concentrate

Pesticides are updated annually. Last updates were done on 6/21 Joey Williamson.

Originally published 09/05

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


Chuck Burgess, Former 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.

Chamberbitter Control: How to Get Rid of Chamberbitter

Chamberbitter, also popularly known as Gripeweed, is an increasingly common invasive weed that has been spreading heavily across regions of the country with more tropical climates. Chamber bitter is a broadleaf weed that sprouts on warm-season grasses annually during the early summer. It is believed that the weed originated in tropical Asia, but it has become a major lawn pest across the southeastern United States from Virginia to Texas.

Chamberbitter tends to prefer growing in conditions where there is excessively high temperatures or areas where there are long periods of drought. Because Chamberbitter is drought tolerant and produces so many seeds, it’s quite a difficult to control weed on landscapes.

If you are having a problem with Chamberbitter, we can help. Our DIY Chamberbitter control guide was developed by our team of lawn care experts to show you exactly what you need to kill Chamberbitter and remove it from your yard quickly and affordably.


Before you can proceed with control of Chamberbitter, you need to make sure that is the weed you are dealing with. Misidentifying a weed can lead to using the wrong herbicide which may be ineffective in treating it, costing you time and money. Here are the traits of Chamberbitter to look for to properly identify it.

  • Chamberbitter looks very similar to the leaves of a mimosa tree and is a member of the spurge family. It goes to seed when it is only about an inch tall and the seeds are actually little balls that develop on the underside of the leaves.
  • Chamberbitter is a slender shrub with alternate leaves that are oblong to almost linear.
  • The stems often branch and can be reddish colored. When they have matured, Chamberbitter can develop a deep taproot which makes this weed particularly difficult to completely remove without the help of chemicals.

Use the above description and image to help you in properly identifying carpetweed. If you are having trouble, you can always contact us and our lawn care experts will help to correctly ID your weed growth and suggest treatment options.


After you have properly identified Chamberbitter, you can proceed with inspection. During this phase, you will need to locate where Chamberbitter is growing, how severe of an infestation is present and the conditions helping it to thrive. Finding this info will help you in knowing where to focus your herbicide application.

Where to Inspect

Chamberbitter is a warm-season broadleaf annual and usually springs up around May or June when the soil temperatures have warmed to approximately 70 oF. It spreads by seeds that are located on the bottom side of the branch. Ornamental beds and turfgrass are the two most common places to find Chamberbitter.

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What to Look For

Chamberbitter grows upright and possesses a well-developed taproot. The leaves are arranged in two rows on the branchlets and are thin and oblong, with smooth margins, resembling a mimosa seed. When mowing Chamberbitter, the seeds can explode and spread everywhere over a large area. If you were able to find chamberbitter and break the stem, a milky white sap would ooze out from the stem, much like other spurge species.


Chamberbitter is a difficult plant to control for various reasons. It grows quickly, can tolerate drought and manual methods of control are not effective because of the seeds which explode spread around everywhere and the extensive taproot which makes hand-pulling a largely useless option because they will just pop up again before long.

Before using any herbicide product, make sure you first have on the proper personal protective equipment (PPE) for safety (gloves, glasses, mask).

A pre-emergent like Isoxaben 75WG would be best so you don’t have to deal with the plant in the first place. Apply 0.38 oz. or 10.5 grams of product per 1,000 sq. ft. For acerage applications, apply 1 lb. of Isoxaben 75WG per acre.

Post-emergently, we recommend controlling Chamberbitter with Celsius WG. Since Chamberbitter is such a stubborn weed, reapplications may be necessary. Celsius WG is selective meaning it will be harmful to the plant you are targeting while providing little to no effect to desirable plants surrounding the weed.

Step 1: Mix and Apply Celsius WG

Calculate the square footage of the treatment area to determine how much Celsius WG you will need. To do this, you will need to measure and multiply the area length times the width (length x width = square footage). Celsius WG should be mixed with a gallon of water at the rate of 0.085 oz. (2.4 g) in a gallon of water per 1,000 square feet. Mixing Celsius WG with a surfactant like Alligare 90 will help the product to stick better to the weed and make the herbicide work more effectively.

For example, if you have a 2,000 sq. ft. area to treat, you will need to mix 0.17 oz. in 2 gallons of water. Once you have made your measurements and calculated how much Celsius WG you need, mix the product and surfactant with the appropriate amount of water in a handheld or backpack sprayer. Shake the sprayer to ensure the solution is well-mixed and then you’re ready to spray.

When applying, change the nozzle setting to a fan nozzle so it will spray a fine mist on the plant and get an even coating on the Chamberbitter.

Step 2: Reapply As Needed

Unfortunately, given how persistent and pesky Chamberbitter is, there is no one and done solution to take care of the weed so keep in mind that repeat application may have to take place in order to fully kill the invaders.

If a second application is needed, apply the herbicide in spot treatments. Repeated applications of Celsius WG should be spaced at 4 to 6 weeks after first treatment. Be careful applying in the heat and just spot treat the area so you don’t burn your grass.

Do not apply more than a total of 7.4 oz. (210 g) of product per acre (0.17 oz. or 4.8 g of product per 1,000 sq. ft.) per year (365 days).


After you have eliminated the Chamberbitter, you don’t want it to come back. Chamberbitter requires a combination of mechanical, cultural and chemical methods to get rid of the weed and keep it away.

  • Make sure you keep a good schedule with mowing, watering and feeding your turf so it is healthy and nutrient-rich, making it better equipped to choke out any invasive weeds that want to establish themselves.
  • Pre-emergent applications of Isoxaben in the spring can help to keep Chamberbitter from making a return and also mulching can help. As long as you are persistent in your efforts to keep Chamberbitter from coming back.

Key Takeaways

What is Chamberbitter?

  • Chamberbitter is a frustrating lawn weed that thrives in tropical conditions.

How To Get Rid of Chamberbitter

  • We recommend a treatment of Celsius WG for post-emergent control or Isoxaben for pre-emergent control to get rid of Chamberbitter.

Preventing Chamberbitter Reinfestation

To prevent Chamberbitter, implement proper cultural practices such as watering, mowing and feeding to make your yard less conducive to Chamberbitter establishment.

Chamberbitter Control

“Timing and persistence is important when dealing with chamberbitter because otherwise your efforts will not stop chamberbitter from repeatedly creeping up. Along with pre-emergent, it will help to put down a good thick mulch to help suppress chamberbitter from emerging. If Chamberbitter is already emerged, 2 4-D is your best option as it will kill the weed but not your grass”