Screening for drought tolerance in Salvia spp. and Helichrysum petiolare: a way to select low maintenance ornamental plants

Recent urban green design strategies rely on the use of plants with low maintenance costs. Thus, the study of drought tolerance in ornamental species is of considerable interest. In this work rooted cuttings of Salvia dolomitica Codd., Salvia sinaloensis Fern., and Helichrysum petiolare (Hiliard & B.L. Burtt) were subjected to five irrigation treatments (T1=20%, T2=40%, T3=60%, T4=80%, and T5=100% of container water capacity - CC) for a total of two months. During this period, to evaluate their recovery responses, all plants were taken back two times for 14 days to the optimal regime of irrigation. Visual plant damages, chlorophyll concentration (SPAD values), leaf area, and growth index were evaluated twice a week. In general, these traits decreased as water stress was intensified. The highest visual damage values and the lowest growth variation were observed in plants subjected at T1. In this stress condition, S. dolomitica and in S. sinaloensis reached a damage value superior to 75% after 16 and 46 days, respectively. In H. petiolare plants, leaf area was significantly reduced already by T2. Slight differences on visual damages among plants at T3, T4, and T5 were showed. Rewatering was effective for all three species only in plants stressed at T3 and T4. Overall, the tested species showed a general tolerance at moderate drought stress and their use in urban horticulture for low maintenance green areas appears feasible.