WUCOLS

Water Use Classification of Landscape Species

This colorful combination of Pennisetum alopecuroides ‘Hamlen’, Epilobium, and Salvia leucantha are good low water use companions for Agave americana. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

This colorful combination of Pennisetum alopecuroides ‘Hamlen’, Epilobium, and Salvia leucantha are good low water use companions for Agave americana. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

Gardening is so very local. But these days we’re all factoring in how much water our gardens require. Making the most of this precious resource when planning and planting involves many strategies: building good soil, applying mulch, and maybe even installing a water catchment system. But perhaps the best place to begin is to get to know your specific region and then select plants according to the amount of water you have, or want to invest in your landscape.

The WUCOLS IV database classifies Symphyotrichum novae-angliae ‘Purple Dome’ as a medium water use perennial for California’s North-Central Coastal, Central Valley, South Coastal, and South Inland regions. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

The WUCOLS IV database classifies Symphyotrichum novae-angliae ‘Purple Dome’ as a medium water use perennial for California’s North-Central Coastal, Central Valley, South Coastal, and South Inland regions. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

Providing just enough water—neither too much nor too little— saves money, avoids waste, and promotes plant health. That lovely perennial (grass, bulb, tree, or shrub) requires differing amounts of irrigation to thrive depending on where you live. This makes perfect sense when you consider the difference between conditions in California’s hot arid Central Valley compared to the cool summers and relatively higher humidity of coastal regions. But you won’t find this sort of regionally specific water use information on plant labels—or even in most gardening books.

Astelia nervosa is classified as a medium water use perennial in coastal regions but is untested or not recommended for hot inland gardens. Here the plant is paired with Genista lydia that has similar water requirements. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

Astelia nervosa is classified as a medium water use perennial in coastal regions but is untested or not recommended for hot inland gardens. Here the plant is paired with Genista lydia that has similar water requirements. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

Nepeta x faassenii. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

The Ruth Risdon Storer Garden in the UC Davis Arboretum features flowering perennials and small shrubs that are especially well suited to Central Valley gardens including Nepeta x faassenii. Photo: UC Davis Arboretum and Public Garden, Ellen Zagory

That’s when California gardeners can turn to WUCOLS IV (WUCOLS stands for Water Use Classification of Landscape Species). The online database classifies and provides regional variables for more than 3,500 commonly available landscape plants.

So before you begin your next planting project, take a moment to explore WUCOLS IV.