Irrigation importance

In 2011, Springer reported that the average U.S. household used approximately 69 gallons of water per capita daily. Some of that water is likely used to install and maintain landscape plants. However, future water shortages may literally change the American landscape if enough water is not allocated to ensure plant survival. Installing and maintaining landscapes can have real environmental and well-being benefits to homeowners; landscapes provide an aesthetically beautiful backdrop, as well as areas for recreation and relaxation (Hall and Dickson, 2011).

Research has shown that better educated homeowners are more likely to adopt conservation measures such as turning off the tap when washing dishes or buying plants that need less water (Gilg and Barr, 2006; St. Hilaire et al., 2010). Households using less water had more concern for conservation issues and future preservation of water resources (Gregory and Leo, 2003). With diminishing fresh water resources, alternatives to irrigating residential landscapes will be in greater demand. Some reductions in the fresh water landscape use might come from using recycled water.

Recycled greywater from washing machines, bathtubs, showers and sinks (but not toilets), constituted approximately 60 percent of the total wastewater from households. This can equate to about 30,000 gallons of greywater a year for a family of four (Al-Jayyousi, 2003; Cabrera et al., 2013). If greywater is treated, it can facilitate groundwater recharge, and may play a substantial role in the reuse and total reduction of fresh water usage by households (Al-Jayyousi, 2003; Eriksson et al., 2002). In the same way, water could also be recycled from nursery production facilities and reused to grow plants. We were curious to learn how consumer perceptions about the source of the water used for plant production and how much water plants used to become established in the landscape affected their decision to buy a perennial or a small tree.

Building on the findings we reported in the June issue (from Knuth et al., 2018, using the same survey, same data, same methodology), we developed two question groups: one for small woody trees and one for herbaceous perennials. We photographed plants and then incorporated additional information about the plants including: (a) price at one of three levels, (b) production with one of three water sources using either fresh water, recycled water, or a blend of fresh and recycled water, and (c) use of irrigation only for the first season to help the plant to become established or use of irrigation for most seasons after establishment1 (Figure 1). The herbaceous perennial plants included were coral bells (Heuchera americana), English lavender (Lavendula angustifolia 'Munstead’), and perennial verbena (Verbena ‘Homestead Purple’) with prices of $6.99, $9.99, and $12.99 per container. The small trees included were golden rain tree (Koelreuteria paniculata), fragrant sumac (Rhus aromatica ‘Gro Low’), and redbud (Cercis canadensis) with prices of $19.99, $29.99 and $39.99 per container.

To compare respondents in different water/drought situations, we used the three categories based on whether they accurately perceived if the region in which they lived was experiencing drought (Knuth et al., 2018). The three categories were based on whether the survey participant accurately perceived if the region in which they lived was experiencing drought and included the following:

• They did not perceive drought even though they were in real drought (NP/R),
• They did not perceive drought, but they were not in real drought (NP/NR),
• They perceived drought correctly since they were in a real drought (P/R).

Consumer preferences

Survey results for perennials showed the major influence on the decision was made based on the plant, which is consistent with prior research. Consumers preferred the perennial verbena more than the English lavender, which was more desired than the coral bells. The second most important factor in the decision to buy the perennial was the water source. Plants grown with fresh water were preferred over plants grown with recycled water and the blend of fresh and recycled water was the least preferred (Figure 2). Lastly, their decision to buy the plant was equally weighted on price and water use in the landscape. So water source was, in the decision process, more important than water use in the landscape. In terms of water use in the landscape, respondents most preferred plants that required irrigation but only for the first season. Lower prices were preferred to higher prices.

In the decision to buy perennials, we found several differences between the drought perception/realization groups. Figure 3 shows the relative utility (or value) placed on the water sources and water uses. A higher score shows the consumers valued that characteristic more while a negative score shows they did not value that characteristic. The water used in the landscape was slightly more important for the NP/NR group compared to the other two groups, both of which had experienced a real drought. In addition, the utility score for “grown in the nursery with fresh water” was lower for the NP/NR group compared to the NP/R group. We also found that the NP/NR group valued less (had a lower utility score) “requires irrigation in the landscape but only for the first season to help the plant become established” compared to the NP/R group.

For small trees overall, plant type was the most important attribute, followed by price, water use in production and least important was water use in the landscape (Figure 4). There was good consistency between the decision-making process for the perennials and small trees. Redbud was the most preferred plant, followed by goldenrain tree and fragrant sumac. Lower priced trees were preferred over higher priced trees. Trees grown with fresh water or grown with a blend of fresh and recycled water were preferred over grown with recycled water (Figure 5). Requiring irrigation until establishment was preferred over requiring irrigation for most seasons. The exception was for the NP/R group who preferred plants that did require irrigation for most seasons. This group had experienced a drought but had not perceived it. For these small trees, this group preferred to irrigate the small tree each season, which would likely require more water. Recall that all three trees appear in the “low” category need minimal irrigation during years of normal rainfall (Costello and Jones, 2014). This would suggest that education about the real water needs of this plant may contribute to changing the consumers’ attitudes about irrigation each season.

Industry relevance

The results of this survey help the green industry understand the relative importance of water source and landscape water use from the consumer perspective. The novel insight is that water source during production and water use while in the landscape were at least as important as price. This finding suggests that there may be some benefit to describing both water source and water needs for plants expected to last more than one season (e.g. herbaceous perennials and woody perennials) in point of purchase information. St. Hilaire et al. (2008) showed educational programs about public water conservation influenced landscape choices from present landscape plants to more water conserving landscape plants. Promotion of low water use plants and the use of recycled water in plant production of those plants may become marketable benefits.

Consumers placed greater relative importance on water source during production over water use in the landscape for both herbaceous perennials and small trees. They preferred fresh water over recycled water and least preferred a blend of fresh with recycled water for perennials and recycled water used for woody perennials. Additionally, the NP/R group, who incorrectly assessed they were not in a drought when they actually were, placed a higher value on nursery plants grown with fresh water compared to those who were actually not in drought and did not perceive one (NP/NR, the comparison group). This finding parallels with what St. Hilaire et al. (2008) found in that, despite scant evidence of the increased risk of disease, recycled water has become more popular only among water conservationists who seek to achieve more efficient ways to use water.

Hurd (2006) suggested that with a focus on consumer attitudes, changes in landscape plant selection could reduce overall water use and reduce future water demand. The attitude that recycled water was not as valuable (lower utility score), especially for the NP/R group shows a great need for education. Consistent with other work, our participants may have preferred fresh water due to concerns about or lack of information regarding the safety of recycled (greywater). Clearly, this is a point for future education, especially for nurseries striving to conserve water resources in other work has shown sustainability concerns by consumers often translate into substantial willingness to pay price premiums. Perhaps the use of recycled water could be more socially acceptable if it were marketed as a means to produce a high-quality product while conserving an important natural resource on the farm or production site.

Our study was the first to combine production water source and landscape water use and show that water source in production and water use needs in the landscape are relatively similar to price in terms of relative importance. This is helpful information for the green industry in that efforts to communicate water source and water needs may be favorably received by consumers.

Funding for this study was provided by USDA SCRI Clean WateR3 – Reduce, Remediate, Recycle Grant Number 2014-51181-22372; USDA NIFA Hatch Projects MICL 02085, MICL 1011569, and TEX0-1-7051; Michigan State University AgBioResearch, and MSU Project GREEN and Texas A&M AgriLife Research.

Melinda Knuth is a doctoral student, Department of Horticultural Sciences, Texas A&M University; Bridget Behe and Tom Fernandez are professors, Department of Horticulture, Michigan State University; Charlie Hall is a professor and Ellison Chair, Department of Horticultural Sciences, Texas A&M University; and Patricia Huddleston is a professor, Department of Advertising and Public Relations, Michigan State University.

¹ The landscape water use categories were derived from the University of California-Davis Water Use Classification of Landscape Species IV (Costello and Jones, 2014). These categories were based on the rate of evapotranspiration expressed as a percentage in reference to evapotranspiration rates in maintained, well-irrigated tall fescue turf. Plants classified in the “high” category need frequent irrigation in during normal rainfall years, plants classified in the “low” category need minimal irrigation during years of normal rainfall, and plants classified in the “very low” category need no irrigation except during years below average rainfall (Costello and Jones, 2014). However, all six plants used in this study appear on the list for low water use plants.