Influence of Irrigation Volume and Mulch on Establishment of Select Shrub Species

In many climates, irrigating shrubs during establishment is critical for long-term growth and survival. However, little research has been conducted to investigate irrigation requirements of newly transplanted container-grown shrubs. During two growing seasons, we investigated gas exchange and growth of newly planted container-grown crapemyrtle (Lagerstroemia indica ‘Victor’), forsythia (Forsythia × intermedia ‘Lynwood’), Vanhoutte spirea (Spiraea × vanhouttei), and photinia (Photinia × fraseri) transplants placed into landscape beds with and without organic mulch. After transplanting, plants were irrigated twice each week at the following rates: 100%, 75%, and 50% of reference evapotranspiration (ETO). In general, each year, transplants with mulch and transplants receiving 100% or 75% ETO-based irrigation had greater stomatal conductance when compared with transplants without mulch and transplants receiving less irrigation. Growth of transplants followed similar trends. However, it is key to note all transplants survived and appeared healthy throughout the growing season. Even transplants receiving 50% ETO were aesthetically pleasing and had growth acceptable for landscape situations. These findings should be useful for landscape irrigation scheduling and for irrigation managers incorporating water conservation into their landscape maintenance programs.