Bareroot liners

This liner study helps better explain how several grower-identified “quality” attributes work together to influence buyer preferences for 1+0 bare root nursery liners.
“We sell only the highest quality nursery liner stock.” That sounds like a rock-solid business paradigm. Production of high-quality nursery stock is a cornerstone principle for sound business management and a sound strategy for successful competition in this industry.

But if you look a little closer, the definition of quality is seldom clearly defined. Other than minimum height and caliper measurements, ANLA guidelines provide few clear standards for quality measurements of nursery liner stock.
 
As a consequence, some growers might just evaluate the overall appearance of a crop while other growers may emphasize overall stock uniformity. Each approach has practical merit and each can be readily measured, but are the assumptions each grower has made about quality the same as their buyers? Are growers missing out on an opportunity to differentiate their liner products and gain a profitable edge on their competition? We cannot answer those questions until we better understand what growers and buyers expect to see when viewing “high-quality” bareroot nursery liners.

Physical attributes of liners
Although physiological measurements are important for predicting liner transplant success and growth potential (carbohydrate storage levels and water use or carbon use efficiencies), gathering physiological data is time consuming, costly and often destructive to at least a portion of the crop. Instead, commercial nursery growers must rely on morphological observations that are practical, can be quickly taught to employees and then used to grade field-grown bareroot liners. At the outset of this project, we informally surveyed bareroot liner producers and identified several individual physical attributes that are likely to be important elements in defining liner quality. Among these attributes were root architecture and uniformities of stem caliper, stem height and canopy architecture. We were also told that price and U.S. region of production were important when assessing nursery liner stock value.
 

We defined a liner as a tree seedling grown for one year either in a seedbed or in field soil, then lifted and barerooted for sale or transplant as nursery planting stock. This type of seedling would also be referred to as a 1+0 seedling.
 
For root architecture, we considered only first order lateral root (FOLR) numbers, which are defined as roots < 1mm diameter that emerge 30mm below the root collar and provide initial root architecture. Other researchers have found that for bareroot liners of several different woody plant species, higher FOLR counts correlate with better transplant success and growth potential. With these basic principles in hand, we set out to determine the relative importance of bareroot nursery liner product attributes in buyer evaluations. 

Setting up the study
To start, we set levels for price, region of production, FOLR number, and uniformities of liner height, canopy density and caliper. We next designed a questionnaire paired with a large, visual display showing nursery liners with various combinations of our attribute levels (Table 1). All display photos were of 1+0 nuttall oak (Quercus nuttallii) bareroot liners because dormant roots and shoots look similar to a wide variety of tree species.  The visual display helped us evaluate buyer purchasing preferences and perceptions of quality through trade-off, or conjoint, analysis. This survey technique allows multiple product attributes and levels of attributes to be analyzed simultaneously. By doing so, we mimic the buying processes by forcing participants to trade-off certain product attributes for others. Statistical analyses are then used to produce utility values and relative importance to purchasing decision weights for each product attribute. Included within our test are pre-determined holdout products, that we can use to judge the accuracy of our conjoint preference model, based on the decisions made by our study participants.

Growers make their choices
We took our survey to the 2007 Southern Nursery Association Trade Show, the Tennessee Green Industry Field Day, the Eastern Region Nursery Tour and the 2008 Mid-States Horticultural Exposition, where we received completed surveys and demographic information from 248 respondents. Our participants were mostly from southern states and more than half had 12 years or more of experience in the green industry. Of those respondents who answered the question, about 85 percent had either bought, sold or grew nursery liners, with half reporting they purchased about 5,000 liners per year and made less than $250,000 per year. Our experimental model was successful in that it could be used to predict buyer behavior and preference based on respondent decisions about the two pre-selected holdout products that we embedded within the display.
 

From our study, we now can better explain how several grower-identified quality attributes work together to influence buyer preferences for 1+0 bare root nursery liner stock. We learned that prospective buyers say that root numbers were very important and they reinforce that belief through choices they make while responding to the graphic display. High FOLR numbers were credited with about 65 percent of the prospective buyer’s decision to identify liners as having high quality. Another 16 percent of their quality evaluation was attributed to uniform canopy density with an additional 11 percent ascribed to uniform liner height. Surprisingly, we found caliper uniformity and price were not very important to respondents and seldom influenced liner preferences after considering the display images. It is possible that our per-liner price range was set too narrowly. Similarly, liner caliper differences may have been too slight to have elicited strong feelings about liner quality.

Comparing attributes
The ranked orders of attributes used to explain liner quality differed slightly between what respondents said was important and what they acted on during hypothetical purchases (Table 2). Price was stated as the 3rd most important characteristic, but was ranked 5th in importance by respondent choices, followed by U.S. region of production, which was least important to participants. 
 
These findings are important because growers can directly benefit by first grading bareroot liners on the basis of larger diameter lateral roots, then secondarily grading liners for uniform canopy form and height. High-quality liners would be expected to command a price premium. In addition, FOLR numbers have been shown to increase for many species when cutting densities in field beds are reduced and uniformity of liner height and canopy density can be managed by pruning and optimized through selection of superior propagation stock.  
 
About the Authors: Drew Jeffers, perennial production foreperson, Zelenka Nursery, Smithville, Tenn. Bill Klingeman, associate professor, Plant Sciences Department, The University of Tennessee. Marco Palma (Department of Agricultural Economics) and Charlie Hall (Department of Horticultural Sciences), agricultural economists, Texas A & M University. This project was undertaken with the help of Dean Kopsell (UT Plant Sciences Department) and David Buckley (UT Forestry, Wildlife and Fisheries Department).