The limitations of any lawn maintenance system are resistant weeds.  After two or three successive treatments, full control over most common lawn weeds is achieved.  However, there are certain difficult-to-control weeds, which may persist, though normally at a low level.  These include creeping oxalis, turf speedwell, nutsedge, paspalum and Poa annua.

Another group of weeds are generally uncontrollable.  These include Kikuyu, couch, etc.