Barnyardgrass, Charles T. Bryson, Bugwood.org
Barnyardgrass, or barnyard grass, is a very common weed in the summer and reaches almost 5 feet in height if it's left to grow in yards. This annual weed has thick stems and forms seed heads from terminal panicles, each one composed of tiny spikelets that disperse and cause more barnyardgrass to pop up in various areas in yards, fields, rights of way and other places.
Killing weeds like barnyardgrass comes down to using pre-emergent herbicides specifically labeled for use on this particular weed. Because a single weed can produce thousands of seeds, it's important to take preventative measures early before the plants emerge. Proper fertilization and watering for the soil and grass species is important. Also, avoid light, frequent water as this can increase the potential for barnyardgrass seed germination in the lawn.