How appropriate for one of the many persistent weeds in the southern garden to have the common name of Gripeweed. Other names include Chamberbitter and little mimosa. I prefer the first name because this weed has certainly given me good reason to gripe about it! Phyllanthus urinaria is a warm-season annual broadleaf weed found growing from the tropics upward as far north as Illinois, but thrives in the lower Southeastern states from Texas to Florida, Georgia, and South Carolina.
Gripeweed makes its appearance in the late spring in our warm climate zones when temperatures rise above 75°F, and will last until late fall with new plants continually popping up. It resembles a mimosa (Albizzia julibrissin) and can also be confused with powderpuff mimosa, native mimosa ground cover (Mimosa strigillossa). It’s a vigorous weed with a long taproot. Plants grow in a mound that can reach one to two feet in height. The 1/2-inch leaves are bright solid green on top with a reddish tinge on the underside. Leaves are arranged alternately on the branches but so close that they can appear opposite one another. I had assumed the leaves were pinnately compound leaves, such as on a black or honey locust, until I looked at them closely. Short branches extend outward on an erect stem that is often red in color. The yellow-greenish-white flowers are tiny. Both male and female flowers are on the same plant with female flowers emerging at the leaf axils from main stem to the middle of the branch. Male flowers emerge at the leaf axils from middle of the branch to the tip of the branch. Many different plants have an order/certain location in which male and female flowers occur; nature can be very detailed. The equally small round fruit produced by the flowers can be found on the undersides of the lateral branches right at the base of each leaf. The Chinese translation of the name is translated to “pearls under the leaves” – a nice description when one considers the trouble the seeds cause in the garden! Seeds produced by the fruit are prolific and are forcibly expelled by the fruit. This method of seed dispersal accounts for the constant reemergence of new seedlings throughout the garden. The only way to establish weed control is to eliminate the new weeds before they produce flowers and fruit.
Gripeweed is in the spurge (Euphorbiaceae) family, but without the characteristic sticky white sap that exudes from the stems of the other members of the family. Spotted spurge is another weed in the garden that I pull continually all summer long. It makes sense that the two are often found together and both are difficult to control. In the 6,400 square foot garden I maintain these days, no chemicals are used for weed control. The choice to stay away from harmful pesticides, fungicides or chemical weed control is a major priority of the owner since the family eats the produce grown in it and appreciates the organic methods used. Weed control can create a major challenge, but it can be done. People ask me how I keep it so weed free. The answer is perseverance. I pull as many weeds as I can every time I visit the garden which is two to three times each week. Also, the entire garden was freshly mulched this spring (wheelbarrow load after wheelbarrow load hand pushed from pile to garden) with some wonderful truckloads of pine/hardwood chips from a local tree company. The mulch is 4 inches deep in the planting areas and up to 6 inches deep around the perimeter and on the garden paths. Mulch helps to keep the weeds down while helping moderate soil temperatures and maintaining soil moisture. I consider the hard work of putting out the mulch well worth the effort. The only areas not mulched are in the actual one-inch rows where vegetables (tomato, summer squash, cucumber, pepper, blueberry, black raspberry) are growing. I don’t like to have mulch touching the stems of the plants but do want mulch protecting their roots as they grow outwards. It is now possible to pull most of the new weeds in just an hour or so each week.
There are chemical means to control this weed especially since it can be a real problem in lawns. I recommend letting a qualified lawn care specialist handle the weed control in your turf to avoid damaging it. Of course, you can visit your local garden center or home improvement store for the latest homeowner remedies. In addition, visit the University of Georgia Extension website for recommendations. If you are a do-it-yourself person, just be careful and follow the labelled directions.