Responses of landscape groundcovers to minimum irrigation.
Four irrigation regimes based on percentages of real-time reference evapotranspiration (ET0) were applied to six widely used species of landscape groundcovers (Baccharis pilularis 'Twin Peaks', Drosanthemum hispidum, Vinca major, Gazania rigens var. leucolaena 'Yellow Cascade', Potentilla tabernaemontani [P. neumanniana], and Hedera helix 'Needlepoint') during a 17-month period in Irvine, California, USA. Irrigation treatments (50, 40, 30 and 20% of ET0) were applied when accumulated real-time ET0 × treatment percentage reached 4.0 cm (1.6 in). Although the response to irrigation treatment was species dependent, B. pilularis, D. hispidum, and H. helix maintained at least minimally acceptable visual quality with applied water equal to 20% ET0, while V. major required a minimum of 30% ET0. Acceptable visual quality of G. rigens var. leucolaena and P. tabernaemontani were not maintained at any treatment. Visual quality of P. tabernaemontani was better at ET0 greater than or equal to 30% ET0, but visual quality of G. rigens var. leucolaena was not improved with more water.