Colorado State Horticulturists Putting Green Thumbs to Work in Determining Best Watering Regimen for Plants

During a drought, watering restrictions on landscapes are often among the first water-conservation safeguards to be put in place. But little research exists about how much water specific bedding plants actually need to be healthy, and homeowners may miscalculate – and even over compensate – their water needs. Experts make educated guesses, but Colorado State University horticulturalists are embarking on a research project to put their green thumbs on exactly what it takes for specific plants to thrive and survive.

The project, part of the Department of Horticulture and Landscape Architecture’s Specialty Crops Program, will be conducted in partnership with Welby Gardens, a private Colorado Front Range company that raises bedding plants. It’s the first research project that attempts to measure the specific water needs of bedding plants in Colorado under typical conditions.

"The onset of drought creates a renewed emphasis on water-efficient landscape plants," said Jim Klett, Colorado State University horticultural professor and Cooperative Extension specialist and a researcher on the project. "Several thousand varieties of bedding plants are sold in Colorado each year, and 300 to 500 new flower and landscape plants are introduced to the state each year. This project helps evaluate and test these plants’ durability in Colorado climate and determine the right plants for the right place in a landscape."

Twenty common annual plants will be selected to begin the project this spring. These plants will be irrigated with five different automated watering regimes in 25 different plots at Colorado State’s Plant Environmental Research Center and in 25 duplicated plots at Welby Garden’s Summer Annual Flower Trials. The experiment will monitor weather with electronic weather stations and evapotranspiration – the amount of moisture that evaporates from the ground each day during that day’s weather conditions – and that information will be communicated to a sophisticated watering clock, which will set different watering rates dependent upon the conditions. Data will be collected twice a week that includes the soil moisture and plant health, which is measured in plant density and growth. Photographs also will be taken to allow the researchers to accurately monitor the visual appeal of the plants over time.

The project will specifically study alyssum, fibrous begonia, dianthus, dusty miller, geranium, impatiens, lobelia, African marigold, French marigold, pansy, petunia, portulaca, rudbeckia, blue salvia, red salvia, snapdragon, verbena, vinca, zinnia angustifolia and zinnia.

Results of the project, along with a pamphlet including photographs of the plants at different water rates, will be made available to Colorado gardeners through more than 2,000 commercial garden centers, nurseries and greenhouses. Results also will be available at Colorado State Cooperative Extension offices and at the 2004 Garden and Home Show.

"This project will help garden centers, nurseries and other horticulture businesses educate the public about ideal landscaping strategies in Colorado while encouraging water conservation and beautiful landscapes," said David Hartley, Colorado State University W.D. Holley Research professor. "The current drought has had a devastating effect on local nursery, greenhouse flower and sod growers, retailers and landscapers, in part because the public is not armed with sufficient information about how much or how little water common landscape plants actually need to be healthy."

The project includes experts Al Gerace, Welby Gardens; Beth Zwinak, Tagawa Garden Center; Steve Echter, Echter’s Garden Center; and Steven Newman, Colorado State Cooperative Extension greenhouse crop specialist.