Untamed Lowcountry

This invasive Lowcountry weed ‘sleeps’ at night and has a rich medicinal history

Chamberbitter (Phyllanthus urinata) is that mimosa-like little weed you may have been pulling out by the handfuls this summer and fall.

It’s a warm-season annual that seems to pop up in lawns, garden beds, and patio cracks almost overnight.

Overall, it’s a delicate-looking plant, several inches to over a foot tall, with small, oblong, somewhat overlapping leaves. The tiny, yellowish-white flowers give rise to round green or greenish-red fruits lining the undersides of the stems.

Native to tropical Asia, chamberbitter has spread throughout much of the world, including the Southeast United States.

Ecologically, the species is a classic example of a successful pioneer plant adapted to colonize, even flourish, in disturbed habitats, especially those created by humans.

Chamberbitter grows well in both sun and partial shade, and in a variety of habitats, including saline and poor soils. As is typical of weeds, it produces enormous numbers of seeds, which can remain dormant for a long time. These are dispersed by water and by animals, including humans.

Also called stonebreaker, shatterstone, and gripeweed, the plant has a long history of use in traditional medicine around the world. In fact, part of chamberbitter’s widespread distribution is due to its deliberate introduction as a medicinal species.

Extracts have been variously used to treat a diverse array of ailments, from kidney stones, diarrhea, and ulcers to hypertension, liver problems, and cancer. And recent bioassays have isolated a host of substances with potential pharmacological uses. Further studies are underway.

Meanwhile, biologists have also been investigating another feature of this common weed: its habit of spreading out its leaves during the day and folding them up at night.

This cyclic pattern of “sleep” movements is an example of a phenomenon called nyctinasty, found in certain other plants, including many legumes.

Depending on the species, such behaviors are associated with a complex of factors, including changes in light and temperature, certain bioactive substances, and specialized cells that swell and shrink in response to a 24-hour clock “perceived” by the plant.

But the adaptive function of cyclic leaf movements in the daily lives of plants is still unclear. Perhaps further work on chamberbitter will help provide some clues.