Weeds are plants that live in a lawn, but are out of place. Weeds require removal to prevent the grass landscape from being aesthetically ruined and to prevent invasive weeds from killing healthy grass. Spraying herbicides on the lawn is usually the best method of dealing with invasive weeds. Without proper weed identification, broad-spectrum, nonselective herbicides are required, which could kill existing grass. Properly identifying the weeds allows the gardener to choose selective herbicides that only target the weeds.
Order a copy of the local weed identification field guide from your nearest university extension service. Field guides contain pictures and identification flow charts that aid in the identification of local weeds. Navigate to your local university's website to see if there is an online version.
Inspect the weed to determine whether it is a broad-leaf plant with flat, wide leaves with net-like venation or a grassy weed that has long, narrow leaves with parallel venation, suggests the University of Minnesota Extension.
Classify grassy weeds by watching as the leaves emerge from the bud shoot. Some grassy weeds uncurl as they emerge, while others are flat and folded. Check the leaf surface to see if it is smooth or hairy.
Inspect the grass stem to see if it is flat or round, to differentiate between species.
Check the root system of grassy weeds to see if the grass has a fibrous root system or a rhizome or root stock; compare to pictures in the field guide.
Compare the shape of the leaves of broad-leaf weeds with the pictures in the field guide. Look at the sets of leaves to see if they emerge from the ground or while above ground. Check the orientation of the leaves to see if they are parallel or staggered.