As in the case of compaction and drainage problems, weeds often provide a telltale clue to unhealthy soil. That is because they are adapted to lousy soil. They can thrive in subsoil and soil that is so lacking in structure, drainage and humus content as to be essentially dead. Cultivated plants, such as grass, can not manage in these conditions, so weeds take over. Clovers, ground ivy, and various thistles are weeds commonly found in lawns growing in poor soils.
Mother Nature has many ways of signalling compacted soil. Simply by identifying the weeds that are growing most commonly in your lawn, you can get a clue. If you have chickweed or plantain in your lawn, the chances are good that you have compacted soil because those two weeds favor areas that have been cultivated and then compacted.