Many weeds in the landscape can cause a gardener to gripe. But when a weed is specifically named after a gardener’s complaint, then you know you have a real problem on your hands.
Phyllanthus urinaria or more commonly, Gripeweed or chamberbitter, is a very common summer annual weed in south Louisiana. It has become more common in in our area over the past 10 years or so. Indeed, it is now one of our most significant summer weeds.
You may not ever totally get rid of it, but you can manage this weed. Gardeners should accept eradication of a particular weed is near impossible, but control and management are within our reach.
Chamberbitter can appear seemingly overnight in flower beds. This summer annual weed can be controlled in beds by hand weeding or using a nonselective herbicide such as glyphosate. Unlike some garden weeds, chamberbitter is surprisingly easy to pull. Hand weeding works well because there are no below-ground bulbs or rhizomes to resprout.
If you are able to apply herbicide just to the foliage of the chamberbitter without getting it on the nearby desirable plants, then you can use glyphosate (Eraser, Killzall, Roundup, Grass and Weed Killer). If desirable plant are nearby, you may consider protecting them. Use a shield when spraying or cover nearby ornamentals with plastic sheeting or bags to prevent the spray from getting on them. If the herbicide gets on the foliage of desirable ornamentals, it will damage or kill them.
Once the weeds have been cleaned out of a bed by hand weeding or glyphosate, thoroughly mulch the bed with 2 inches of mulch to minimize new weeds showing up. The mulch will suppress the germination of the chamberbitter seeds in the soil. The thickness of the much is important for effective control. Using 2-4 inches of pine bark or 4-6 inches of pine straw will work best for weed suppression.
Chamberbitter does not respond well to some preemergence herbicides, but isoxaben is recommended in some publications. After hand weeding or killing with glyphosate, apply a product containing isoxaben (such as Green Light Portrait Broadleaf Weed Preventer) following label directions. But proper mulching in concert will do a great job suppressing weed seeds.
If you have St. Augustine, centipede or zoysia, spot treat with atrazine during the summer. It is too hot to apply it over the entire lawn, but you can spray spots or patches of the chamberbitter weed where they occur. Make two applications following label directions.
Also, mow your lawn at the highest recommended height to make it more competitive – St. Augustine at 3 inches, centipede and zoysia at 2 inches.
It’s bad enough having weeds in the lawn and flower beds, but the weed might be telling you there is yet another problem occurring in the landscape. We call these weeds indicator weeds. A bad chamberbitter infestation in a lawn may indicate a lawn that is in poor vigor. Chamberbitters have a harder time establishing in a thick, healthy, vigorous lawn. Make sure you provide your lawn proper care (mowing, watering, fertilizing, sun) to minimize chamberbitter problems.