Responses of Turfgrass and Ornamental Landscape Species to Prolonged Drought Stress

Water resources are depleting as the world’s population continues to grow.  It is not uncommon for water municipalities to impart water restrictions on residential landscapes causing plants to experience drought stress.  This study evaluated the performance of one cool-season turfgrass (Poa pratensis) and eight common landscape species (Achillea millifolium, Ajuga reptans, Liriope muscari, Pachysandra terminalis, Sedum album, Thymus serpyllum, Vinca major, and Vinca minor) during a severe dry down and recovery thereafter in a greenhouse study in Manhattan, KS.  The study was conducted twice, once in the spring and again in the fall of 2010.  During the dry down, several species deteriorated faster than others to the lowest quality rating of one (1-9 scale, 1=dead/dormant and 9=best quality).  Sedum album consistently performed the best during each study, taking ~266 days to decline to a quality rating of one.  Liriope muscari and Pachysandra terminalis also performed well with a mean range of 62.3 to 122 days.  Vinca minor and Vinca major declined faster than the previous three species, averaging 48.3 to 78.6 days to drop to a quality rating of one.  Finally, Achillea millifolium, Ajuga reptans, Poa pratensis, and Thymus serpyllum performed the worst by declining to a quality rating of one within 39 to 73 days.  Poa pratensis, Ajuga reptans, Vinca major, and Sedum album were the only species to recover in the first study, with 30% to 60% recovery after sixty days.  None of the species recovered during the second study probably because of more severe vapor pressure deficit caused by artificial lights that were needed in the fall, which caused the pots to dry down faster.  Results from this study indicate Sedum album, Liirope muscari, and Pachysandra terminalis would be most successful in landscapes where severe drought may occur.  In landscapes with intermittent or less severe droughts, Vinca minor and Vinca major may also be good selections, as well as Poa pratensis and Ajuga reptans if periods of dormancy are acceptable to homeowners.