How much water a plant needs is influenced by several factors. Not only is the individual plant size and species important, but also the growing conditions. Light, temperature, humidity, container type, container size, and finally soil type all influence the speed of growth and therefore the amount of water needed.
It is best to look up individual plant types for their watering needs. Typically, you will see the following descriptions under water requirements: plants enjoy constantly moist, but not soggy wet soil; plants prefer to have soil allowed to dry moderately between waterings; or plants prefer very slightly moist soil at all times. The succulents and cacti have differing needs during their growth cycle.