Chamberbitter

What is chamberbitter?

Chamberbitter is a warm-season annual broadleaf weed that came to the United States from tropical Asia and now turns up in lawns, flower beds and nursery pots across the Southeast. chamberbitter identification is mostly about the leaves and the seed pods: each side branch carries two tidy rows of small oval leaves, so the plant looks like a seedling mimosa tree, and the round, warty seed capsules sit in a line along the underside of those branches.

It is a problem because it grows fast, sets seed quickly and spreads that seed by force: ripe capsules split and throw seed away from the plant, so a few plants left to ripen can seed a much bigger patch next year. UF/IFAS notes that plants kept just 2 inches tall can still reproduce, so mowing does little. Once the stem base turns woody, it gets much harder to kill.

Chamberbitter identification: what to look for

Get down close and lift one of the leafy side branches. Look for the two rows of little leaves, then flip the branch over and check for the round seed capsules tucked under it. Snap a stem too: unlike many weeds in the spurge group, chamberbitter has no milky sap.

• Leaves: Small, oblong, smooth-edged and hairless, lined up in two rows along thin branchlets so each branch looks like one compound leaf. Dark green on top, reddish green underneath, closing at night.
• Stems: Slender, branching, often crimson red, angled or grooved, with no milky sap. Older plants turn woody at the base.
• Seed pods: Round, warty, three-part capsules about 1/8 inch wide, attached singly with no stalk along the underside of the leafy branches.
• Roots: A well-developed taproot. Pulling goes easier when the soil is moist.
• Growth habit: Upright and heavily branched from the base; about grass height in a lawn, but it can mound to 1 to 2 feet where unmowed.

Where it grows in the United States

Chamberbitter is a weed of the warm Southeast. NC State lists it across North Carolina's coastal, Piedmont and mountain regions, and University of Georgia turf scientists record it in Alabama, Georgia, Florida and Texas, roughly USDA hardiness zones 7 through 10. It needs warm soil to sprout, so it is a summer weed that lingers into late fall and can grow year-round in subtropical Florida.

Around the home it favors sunny spots with moist soil: irrigated lawns, well-watered beds, gravel areas and the soil of potted nursery stock, which is how it often reaches a new yard.

Chamberbitter look-alikes

A few plants get mixed up with it:

• Long-stalked phyllanthus (Phyllanthus tenellus): A close relative found in the same places. Its seed capsules hang on short stalks about 1/4 to 1/2 inch long, while chamberbitter capsules have no stalk. It also has longer, less branched stems and can reach 2 feet.
• Mimosa tree seedling (Albizia julibrissin): Young mimosa trees have similar feathery foliage, but they do not carry rows of warty seed capsules under the leafy branches. Chamberbitter looks like a mimosa in miniature.
• Sunshine mimosa (Mimosa strigillosa): A native Florida groundcover with fuller, lusher foliage and bright pink, puffball flowers. Chamberbitter has only tiny greenish flowers.

How to get rid of chamberbitter

Pulling, digging and mowing: Hand pulling works well in beds and small lawn patches. Pull young seedlings when the soil is moist so the taproot comes out, and get them before capsules ripen; once seed is on the plant, every pull risks scattering it. Scout often through summer, then cover cleared beds with 2 to 3 inches of mulch. Do not count on mowing.

Cultural control matters most, because the right conditions keep it from coming back.

• Keep turf thick and healthy by mowing at the right height and avoiding stress from insects, disease, drought and poor fertility.
• Spread 2 to 3 inches of mulch in beds each spring. The seeds need light to sprout, so mulch blocks them.
• Cut back irrigation where you can; chamberbitter and its seedlings thrive in moist soil.
• Inspect the pots of new nursery plants and pull any chamberbitter before you plant.

Herbicides: Spray early, while plants are small, because control drops off once stems get woody. In lawns, Clemson Extension lists atrazine (centipedegrass and St. Augustinegrass only) and isoxaben (tall fescue, centipedegrass, St. Augustinegrass, bermudagrass and zoysiagrass) as preemergence options, applied in late spring and again about eight weeks later, though NC State notes most preemergence products perform poorly on this weed. For emerged plants, three-way mixes of 2,4-D, mecoprop (MCPP) and dicamba can go on in late spring or early summer and again about a month later, with extra care on centipedegrass and St. Augustinegrass; a thiencarbazone, iodosulfuron and dicamba combination and atrazine are other warm-season lawn options. Avoid most postemergence lawn herbicides during spring green-up. In beds, spot-treat with glyphosate, shielding ornamentals and keeping it off the lawn, and consider isoxaben under mulch around established shrubs. Use only products labeled for your site and grass type; the label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Most chamberbitter starts from seed, either from last year's plants or from a nursery pot. Check new container plants before planting, and pull every plant before it ripens capsules.

Keep beds mulched 2 to 3 inches deep, water only as needed, and maintain dense turf. Where pressure has been heavy, a labeled preemergence product in late spring, before soil hits about 70 degrees, can cut down the next flush.

Questions we get about chamberbitter

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