Knowledge of weed biology is essential for development of both economically and environmentally acceptable weed management systems. Weed biology relates to plant attributes such as morphology, seed dormancy and germination, physiology of growth, competitive ability, and reproductive biology. Concepts of population biology such as seedbank dynamics for annuals and root reserves, dormancy, and longevity of vegetative propagules for perennials can be used to predict weed infestations better and to evaluate sustainable management strategies. Integrated approaches that give priority to depletion of root reserves or seedbanks through interfering with dormancy or germination requirements have great potential to enhance weed management strategies in the future.