These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area. While there are several top candidates, probably the number one difficult weed problem in area lawns is ground ivy, or creeping Charlie. Although it is unlikely you will totally eradicate this weed, there are a variety of ways to keep it under control in the lawn.
Ground ivy is an aggressive weed that can tolerate shade and poorly drained soils.
Lawns growing under these conditions tend to be weaker and thinner, so the ground ivy easily invades. Often extensive patches are formed in shade and sun areas. Ground ivy has square stems, purplish blue funnel-shaped flowers, and round to somewhat kidney shaped leaves with rounded, toothed margins. Crushed leaves have a minty odor. Adjust management practices in shade areas to help maintain a thicker, vigorous lawn.