Grouping plants into hydrozones is an approach to irrigation and planting design where plants with similar water needs are grouped together.
Ideally, each zone of the irrigation system will supply plants with the same water needs with the appropriate amount of water.
Unfortunately, many irrigation systems are set to water all plants in the landscape at the same time and rate. This approach is wasteful of water.
When creating a new landscape plan, be sure to account for plant water needs. Information on water needs of adapted water-wise plants can be found through the Cooperative Extension Service offices and knowledgeable staff at reputable garden centers and nurseries.
Once water needs of plants are identified, categories such as Routine Irrigation, Reduced Irrigation, Limited Irrigation and No Irrigation can be created. Label these zones with specific water requirements such as Routine Irrigation needs watering every 2-4 days and Limited Irrigation needs watering only during dry spells once plants are established.
These categories can be identified as roughly drawn bubble areas on the plan. When planning for hydrozones also keep in mind the uses of the spaces to be created. A lush "oasis" or higher water use zone can be created closer to the house while a more natural area with low water needs could be placed at the back or edges of the property.
Retrofitting an existing irrigation system can be more difficult and professional consultation may be necessary.