Chamber Bitter Phyllanthus urinaria

Chamberbitter is a flowering summer annual, native to Asia, in the polkweed family. It is heavily branched at the base with ascending stems, often forming a mound 1 to 2 feet in height. Leaves are oblong in shape, 1/2 to 3/4 inch in length, on short branches, and look similar to compound leaves of some legumes. Unlike other weeds in this family, chamberbitter stems do not exude a milky sap when broken. Flowers are small, inconspicuous, and greenish-white. Distinctive round fruit are borne on the undersides of the lateral branches at the leaf axils.

The plant requires warm soil and full sun. The large amount of seeds produced and the extensive root system of this plant make it very competitive with other nearby plants.

Similar in appearance to long-stalked phyllanthus (Phyllanthus tenellus), the two species differ by the length of the seedpod stalks. Chamberbitter fruit are borne sessile (without stalks) whereas long-stalked phyllanthus stalks are about 1/4 to 1/2 inch long. Phyllanthus require substrate temperatures above 75 degrees F to germinate and thus are more common in the summer, but will persist into late fall in the southeastern US (and year-round in sub-tropical areas). Plants flower throughout the summer and fall then die after frost. Fruit forcefully expel seed short distances.

Chamberbitter is listed as an invasive species in Alabama. The Clemson University Home and Garden Information Center has an factsheet on mechanical and chemical controls of this weed.

Insects, Diseases, and Other Plant Problems: 

Both species of Phyllanthus are particularly difficult to manage. Do not let plants go to seed. Inspect pots before planting and eradicate new infestations before they can spread. They are poorly managed by most preemergent herbicides labeled for use.