Long-stalked phyllanthus, Phyllanthus tenellus, is a perennial weed moving into our landscape and turf settings. The following is more information from the University of Maryland.
Long-stalked phyllanthus has been a weed found mostly in nurseries and greenhouses and has been spreading through movement of these ornamental plants. Mostly found to the south of Maryland, it is now appearing in many new areas as plant materials are shipped each year to meet the landscape market. Long-stalked phyllanthus is an erect perennial growing to eighteen inches in height. It germinates in the landscape as temperatures get warm and when the soil is moist. The leaves are alternately arranged on a central stem in two rows. Leaves are elliptical to oval in shape, having no petiole, and with a slight projecting tip at the apex. Stems are erect and both leaves and stems are without hairs. Flowers are small, white to green, and grow on a flower stalk that starts from the area between the leaflet and the central axis of the leaf. The fruit of this plant will be round, green, and may hang below the leaves.
Control of this weed starts with the removal of it from all containers prior to planting in the landscape. Evaluate the plants prior to placement. Once established it becomes harder to control. It is resistant to many of the commonly used pre emergent herbicides including Preen, Surflan and Barricade. The seeds of long-stalked phyllanthus are very small so the appropriate use of mulch will help prevent this from germinating. Large nugget mulch allows the seed to stay dry and not have the sunlight needed to germinate. Post emergent materials that are successful include diquat, glufosinate and glyphosate. Again consider cultural controls first.
Reprinted from and article by Chuck Schuster in the October 30, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Oct30L.pdf