But when it appears as a clump amid Bermuda grass or Kentucky bluegrass, it is considered a weed. Weed seeds permeate most soils by the millions. One common lawn weed, purslane, can produce more than 2,000,000 seeds per plant in a single season. Some seeds remain alive in the soil for many years, which is why it is good to kill all existing weeds before putting in a new lawn. Although this will not guarantee permanent freedom from weeds, it does cut down on them substantially while the n ew lawn is becoming established.
Weeds gain a foothold more easily in lawns that are poorly maintained.
Overwatering or underwatering, fertilizing too little or too much, and mowing too low can all tip the balance in favor of weeds. So can excessive wear, disease or insect damage, soil compaction, poor drainage, too much shade, or any condition that exposes the soil to extra light. If your lawn has many weeds, the first step is to correct any underlying lawn care problems. Creating a healthy climate for your lawn can automatically create an unhealthy one for weeds. Be sure to read the sections on watering and fertilizing your lawn.