Times and intervals for watering differ according to the type of plant. The most important factor to remember is the depth of the root zone and soil composition. The deeper the roots and the finer the soil, the longer the watering time must be, but frequency of watering will be reduced. A finer soil such as clay, with which most of us are blessed, cannot absorb water very quickly, but will hold the moisture for a longer period of time. Shallow root zones and sandy soil types will require frequent watering of a shorter duration. Observe plant and soil moisture conditions and adjust watering times and intervals to maximize plant growth and minimize water use.
In a system with mixed plantings, some compromises may have to be made between plants that require occasional deep watering and those that prefer frequent shallow watering. This can be partly accomplished by using emitters of higher output on the deep-rooted plants. If this is not practical because of other factors, a compromise can be reached by doing shallow watering on a frequent basis as well as occasional deep watering. The first irrigation cycle should be a much longer one than normal. You will want to completely establish the wet zone in each plant’s root zone. This cycle should be from 1 hour up to possibly 6 hours, depending on the plant material that you’re watering and the type of soil.