Professor in Forest Resources at the UW School of Environmental and Forest Sciences .
Kim ’ s research dream , officially known as the Climate-Ready Landscape Plants Project , has come to fruition in the grassy field south of Merrill Hall at the Center for Urban Horticulture ( CUH ). The 0.4-acre research site , known as Plot 1 , is filled with precise rows of roses , mock-orange , mahonia and other popular species being maintained by students and visited by pollinators .
The UW is one of six universities in western states conducting this plant irrigation trial . University of California , Davis ( UC Davis ) originated the project , which is designed to assess plant performance under three different irrigation regimes . Those that do best under low-water conditions will be recommended to the green industry . The trial ’ s hard data will guide nurseries in choosing appropriate plants to propagate and market for Western North America ’ s shifting climate .
One of the project ’ s major goals is to move away from anecdotal to more rigorous , robust data about plants ’ water-use characteristics . “ This trial is significant because it really does put data to the observations — not just qualitatively , but quantitatively — about how plants are performing ,” explains Ray Larson , Curator of Living Collections at UWBG . “ I think this is the type of research that people are going to be increasingly interested in .”
Trials Methodology Protocols and requirements are exacting , as all six sites must precisely adhere to the same methodology established by UC Davis .
The UW trial is testing 15 plants at three different irrigation volumes . “ So 15 times three is 45 , which is replicated eight times for each treatment in each species . So we have 360 plants total ,” explains Kim .
Year one is the establishment phase , during which all plants receive the same amount of water in the summer . Irrigation ( of the non-rainfall variety ) will be suspended during the winter .
Year two , known as the deficit year , begins in spring 2022 , and is when the three different water treatments ( low , moderate and high ) commence . In other words , that ’ s when the rubber hits the road , and the plants will begin to respond and grow at different rates .
The amount of irrigation delivered will be determined by evapotranspiration ( ETo ) data obtained from the WSU AgWeather weather station , located a mere 50 meters from the plot . ( Evapotranspiration is the water lost to the atmosphere both through evaporation from the soil surface and transpiration by plant leaves .) Some researchers and farmers have to rely on weather data from stations hundreds of miles away , so the UW ETo data is enviably accurate . Arthur Hsin-Wu Hsu , a Ph . D student in the UW School of Environmental and Forest Sciences ( SEFS ), checks the data daily and makes adjustments to the irrigation as necessary .
During year two , graduate students will rate the plants ’ health and aesthetics in the following categories : foliage , flowering , pest tolerance / disease resistance , vigor and overall appearance ( AKA , the “ WOW factor ”). The plants that thrive best with the lowest amount of irrigation will be the “ winners ”, so to speak .
How the Plants Were Chosen All 15 species are suited for full-sun exposure . Six are common to all participating universities ; the remaining nine , which reflect the tastes and climate of our region , were selected by the UW team based on advice from Larson , who is the Plant Advisory Committee representative for UW ’ s trial . To build the list , he consulted with Seattle-area peers in the horticulture and nursery worlds , including the well-regarded Great Plant Picks team ( greatplantpicks . org ). “ It was a chance to nerd out a bit ,” he laughs .
To make the selections , he points out , it was important to have good knowledge about what growers are propagating , nurseries are selling , and what consumer trends are . “ Plants fall out of fashion , just like clothes ,” he points out .
Larson is particularly interested to see how Vitex agnus-castus Blue Diddley ® fares . It is a dwarf version of the chaste tree , which some gardeners shy away from due to its potential to become quite wide and tall — in other
Fall 2021 v 11