Signalgrass is a summer annual grassy weed that is also known as Alexandergrass or by its scientific name, Brachiaria plantaginea. This lawn weed gets its name from its seed heads that resemble signal flags.
Signalgrass can be identified as a summer annual grassy weed with a horizontal and creeping growth habit. It features smooth stems, rooting at the nodes, and leaf blades that are typically smooth, flat and wide. Its leaf sheath often includes hairs on margin. This lawn weed also features seed head branches that spread like signal flags with seeds on underside—hence the name Signalgrass.
Signalgrass is a lawn weed that prefers disturbed areas and can often be found growing in lawns. This grassy weed is found in most parts of the southeastern United States. These grassy weeds are also summer annuals, meaning they begin to grow (germinate) in the spring, mature in the summer and then produce seeds and die by the fall or first hard frost—an entire life cycle completed within 12 months.
Its short, broad leaves and low growth habit may make Signalgrass easy to distinguish from other types of grass and grassy weeds; however, it's these same features that make it difficult to control when present in your lawn. Cultural control methods—such as hand-pulling lawn weeds or proper watering and mowing—are largely ineffective. For effective weed removal, professionally selected and applied weed control treatments are your best bet for eradication.