It depends on the types of plants. Generally, irrigating helps plants stay green and moist and less likely to burn. In arid environments, irrigation is necessary to keep most plants alive. However, some plants become overgrown when watered and create too much fuel, becoming a maintenance headache. Some plants can be mowed or cut back at the beginning of the fire season and then irrigated very infrequently so they don't grow during fire season. Some drought-tolerant plants stay low and green with minimal irrigation and can be damaged or killed by over-watering. To facilitate proper plant care, zone your landscape for these different irrigation needs.