If you’re not sure whether or not to water, do this: pull back any mulch, and dig a hole about 10-12 cm (4-5 in) deep. Take some soil from the bottom of the hole and try to squeeze it into a ball. If it sticks together, you don’t need to water (unless you have a bunch of young, small plants with short roots). If the soil does not stick in a ball, you may need to water. Sandy soil (see soil) will not ever form a ball, but if it sticks to your fingers, it’s wet enough.
However you water, it’s best to water thoroughly (meaning, wetting the soil to a depth of 12-15 cm/5- 6 in). Getting water down that far encourages plants to grow deep, strong roots. Getting water that deep can take considerable time, and as a result, most gardeners tend to water too shallowly. There is no single recommendation for how long to water, but if your soil seems to be dry based on the test above, it may take as much as several hours to water your garden thoroughly (the method you use to water will determine the time it takes).
