260 To develop items with phrasing familiar to respondents (Dillman 2000), interviews about plant species diversity with 13 nursery professionals in Oregon, U.S., were taped. This was important because of potential confusion in terminology. In the green indus- try, “diversity” is used for genetic or multi-cultural differences as well as for new colors of common plants. “Overplanting” can refer to over reliance on plants with limited genetic range or to crowd- ing large quantities of plants in an area for immediate impact. Ten horticulture or landscape architecture faculty members in Wash- ington, Idaho, and Oregon reviewed the survey for content valid- ity, and it was given to five students to ensure that it was reliable and easy to understand. The Washington State University Hu- man Subjects Institutional Review Board approved the research. Respondents A list of companies with nursery licenses was acquired from the Washington State Department of Agriculture in 2007. Companies that were exclusively retail, had gone out of business, were not in- volved with plant production, or did not answer the phone number listed were removed, yielding 130 active wholesale nurseries. A description of the anonymous survey was sent to the person respon- sible for plant inventory decisions at each nursery. Two months later, a follow-up e-mail was sent to encourage participation. Completed surveys were obtained from 42 people in the whole- sale nursery industry in Washington state. This response rate of 32% falls within an expected range for businesses (Dillman 2000). Most of the respondents were owners of the business con- tacted (75%) and had worked in the industry for more than 15 years (69%; range of 3 to 68 years). The nurseries ranged in size from 0.5 to 500 acres (mean of 28 acres, median of three acres) and produced a wide range of crops, including veg- etable starts, bedding plants, native plants, flowering shrubs, and shade trees. When asked how much acreage was devot- ed to producing their primary crop, responses ranged from 0.02 to 500 acres (mean of 19 acres, median of one acre). Data Analyses Responses of “strongly disagree,” “disagree,” “slightly disagree,” “slightly agree,” “agree,” and “strongly agree” on all diversity statements were scored from one to six, respectively, and used to calculate a mean attitude for each statement (Appendix). Respons- es on seven statements (four where agreement could indicate an understanding of diversity and three where agreement could in- dicate a lack of understanding) were combined to create a “Plant Species Diversity Score” (Appendix) by summing the scores for the statements after converting them so that a higher value was associated with fuller understanding of diversity. Analysis of Variance was used to compare the Plant Species Diversity Score to demographic items. A significance level of 10% was used, so that possible relationships were unlikely to be overlooked and because the consequences of error in interpretation were minor. RESULTS AND DISCUSSION General Knowledge of Plant Species Diversity Issues Nearly all respondents (85%) were in agreement that “increasing the number of different plant species used in an area is important ©2011 International Society of Arboriculture Polakowski et al.: Survey of Wholesale Production Nurseries for biodiversity” (Appendix). The mean attitude of 4.78 indicated that most respondents have an awareness of plant species diversi- ty issues. Responses on other statements, however, indicated their level of understanding may not be very deep. Only 56% indicated agreement that “lack of plant diversity in a given region is an eco- logical problem.” The mean of 3.83 suggested that most people only slightly agreed with this statement. These two statements are similar; however, there is more of a value judgment involved in answering the second statement, which used the word “problem.” Many respondents apparently saw no “problem” with the wide usage of particular plants. Promotion of the wide usage of partic- ular plants is common in the media. This can be readily seen in ar- ticles encouraging people to replant American elm (Ulmus ameri- cana) with the small number of clones that are resistant to Dutch elm disease (Duffy 2009). Instead of promoting the prudent use of these clones, such articles often inadvertently promote the re- creation of the circumstances that led to the elm’s original demise. Only 45% of respondents agreed that “planting more than 10% of the same plant species in a region greatly increases the risk of insect or disease outbreaks” (Appendix). This was unex- pected, because the general 10-20-30 rule (plant no more than 10% of any species, 20% of any genus, or 30% of any fam- ily) has been widely discussed (Santamour 1990; Galvin 1999; Frank et al. 2006; Sydnor et al. 2010). The lack of full under- standing of the need for increased biodiversity is supported by the fact that only 40% agreed that “planting large numbers of a single plant species in a commercial or residential landscape increases the likelihood of severe insect or disease outbreak.” On statements where agreeing may indicate a lack of aware- ness of diversity (Appendix), agreement ranged from 59% for “elm trees that have died from Dutch elm disease should be replaced with the new disease-resistant elms” to 83% for “the wholesale nursery industry is already addressing the species di- versity issue, because they frequently introduce new plants for customers.” While agreement may indicate a lack of understand- ing of diversity issues, the means, which ranged from 2.56 to 3.22, suggest the respondents were neutral or only slightly agreed with the statements. Views that are not strongly held, such as these, can be easily changed with education (Schafer and Tait 1986). Role of the Nursery Industry on Plant Species Diversity Issues Agreement with the statement that “most wholesale nurseries currently offer an adequate range of plants for their customers to choose from” was very high (78%) (Appendix). This attitude is not supported by the results of a study that found that only 3% to 5% of trees desired by urban foresters in Ohio were avail- able from nursery growers in Ohio (Sydnor et al. 2010). Agree- ment that “the nursery industry could easily add more species to their inventories” was also high (67%). This is important if the issues with lack of diversity are to be addressed. Only 24% agreed that “voluntarily increasing the number of differ- ent plant species in their inventories would allow nurseries to avoid regulatory interference from state or federal authorities.” Nursery Characteristics and Plant Species Diver- sity Awareness Plant Species Diversity Scores ranged from 13 to 38, with a mean of 24 (possible range was 7 to 42, with higher numbers indicat-
November 2011
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