Knowledge of the lifecycle of troublesome weeds is crucial for devising successful Integrated Weed Management (IWM) strategies. This is particularly useful when potential lifecycle weaknesses are identified and exploited by management. Grouping weed management by lifecycle similarity is intrinsically attractive, particularly when a large numbers of weeds are encountered. This idea was examined for the botanically diverse weed flora in the Australian cotton industry. The lifecycle of 32 weeds was examined. This information was drawn from the literature, unpublished field observations and from field studies on the lifecycle of problematic species. The literature revealed four weed groups, those with emergence and reproduction: - year round, in all but winter, between mid-spring and mid-autumn, and those with defined warm season periods. These generalised groupings allowed major gaps in management to be identified, in particular in fallow, pre-plant and post-harvest situations. Individual weed species have different lifecycle characteristics, despite apparent similarities. Failure to recognise these are a key reason why problematic weeds sometimes arise. The lifecycle (field) studies revealed different defined periods of growth and reproduction which could be exploited. These studies indicate that while IWM strategy generalisations can be made based on lifecycle similarity, that specific studies and management of problematic weeds will often be needed.