The present invention provides systems and methods in which a microprocessor, disposed in an irrigation controller, is programmed to adjust an irrigation schedule according to a condition of a plant being irrigated. The adjustment to the irrigation schedule may be to the entire irrigated site or only to a portion of the irrigated site. The irrigation schedule may be at least partly derived from ETo data and may be from current ETo data, estimated ETo data or historical ETo data. The condition may be plant establishment, plant maturity or plant health.