2018 ASHS Annual Conference

Recycled wastewater is a popular alternative water resource. Recycled water typically has a higher salinity than potable water and therefore may not be an appropriate water source for landscapes planted with salt-intolerant plant species. Our previous research demonstrated that recycled wastewater could be detrimental to the growth of long-lived conifer species. We hypothesized that recycled wastewater might also be detrimental to the growth of perennial landscape species. To test our hypothesis, we established a research trial in which we grew varieties of popular landscape perennials ( Calibrachoa, Calamagrostis, Deschampsia, Fuchsia, Guara, Hemerocallis, Heuchera, Lantana, Lavandula, Rosa, Salvia) in pots in a greenhouse with irrigation sourced from recycled municipal wastewater or potable water. In a parallel experiment, we tested the growth responses of six of these varieties (Calibrachoa, Fuchsia, Guara, Lantana, Lavandula, Salvia) to elevated levels of irrigation salinity (EC 0.5, 2.5, 6.0). The final component of our study was to determine if the differences in growth between recycled water and potable water were discernable by the public, which could reduce the saleability of these plants. To learn public opinion, we masked the treatment irrigation (recycled or potable water) and surveyed the desirability of the different plants based on a variety of aesthetic qualities. Our results showed that there were no significant growth differences between the plants grown with recycled wastewater and plants grown with potable water (p > 0.05). Accordingly, the public perception was not affected by the irrigation treatment. There is little public research available reporting how people chose plants for their yards. Our plant preference survey can inform researchers and industry members about the acceptability of new species or cultivars that may have certain functional qualities, like drought tolerance, yet may not lack other aesthetic qualities, like lack of flowers. Our results strongly suggest that recycled wastewater is a suitable source for cultivating perennial landscape species. However, the results of our increased salinity trial revealed significant ( p < 0.05) negative effects on plant growth at 2.5 and 6.0 EC levels compared with 0.5 EC. These findings suggest that in landscapes were salts will accumulate, such as locations with insufficient leaching that salinized recycled water may present a threat to long-lived herbaceous perennial species.