SCIENCE TO THE GROWER: Is sustainable ornamental crop production sustainable?

by Richard Evans

The theme of this issue is insects, but I don’t want to write about them. I hold no particular grudge against insects, but I’ve never been able to maintain a lasting relationship with any. One little critical remark from me and they’re crushed. To assuage my guilt, I’m going to write instead about the science of being green, sustainable and local in the ornamental nursery industry.

Organic crop production, once the domain of a committed subset of producers, has been more widely adopted recently, in part because the perceived value added may enable growers to compete more effectively in niche markets. Even ornamental crop producers have been urged to adopt practices that permit them to paste ecolabels on their plants. So, in addition to having to compute the economic costs and benefits of organic and sustainable crop production, growers must assess the strength of consumer demand for plants that satisfy the current enthusiasm for organically, sustainably and locally grown crops.

A group of researchers in the Midwest has investigated this issue (Yue and others 2011). They surveyed 834 people in Indiana, Michigan, Minnesota and Texas who had bought ornamental plants within the previous year. The researchers asked participants how many plants they had bought, and what type, then asked how inclined participants were to buy conventional plants; sustainable plants; organically grown plants; locally produced plants; plants grown in energy-efficient facilities; and plants grown in biodegradable, compostable, or recyclable pots.

What did the researchers find? Participants were not enthusiastic about organically grown plants, and were only mildly inclined toward plants produced sustainably or efficiently. Consumers were enthusiastic about plants that were locally grown, or produced in biodegradable, compostable, or recyclable pots. In their search for correlations, the researchers found that people with young children were most likely to be interested in organically grown plants (probably out of fear of what those kids otherwise might say when they become teenagers). Also, the older the participant, the higher the interest in compostable pots. (That stands to reason, since the older the participant, the closer he or she is to looking and feeling like a compostable pot.) Purchasers of perennials within the past year were more interested in buying sustainable and locally grown plants. Purchasers of shrubs within the past year were also interested in sustainable plants. However, purchasing a tree had no subsequent relationship to interest in “green” production. (Perhaps tree buyers feel that their work is done here.)

One wonders how applicable this study is to other parts of the country. The researchers did find that participants from different states had different levels of interest in these plant types and production methods: people from Indiana were least interested in plants that came from energy-efficient greenhouses or were grown in biodegradable and compostable pots. The authors didn’t offer a reason for the unusual behavior of Indiana’s people. (I could furnish one, but lack sufficient space.) In any case, I wouldn’t be surprised to find that attitudes in favor of sustainable and organic production are stronger in California.

The authors conclude that consumers are more interested in sustainable pots than in sustainable plants. So let’s briefly consider sustainable pots. Biocontainers, which are not petroleum-based and decompose quickly, have been around for a long time, but more options have become available within the last decade. Some of the most detailed studies of their physical properties have been done by Michael Evans’s group at the University of Arkansas (Evans and others 2010; Beeks and Evans 2013). (By the way, Professor Evans and I are not directly related, but it is possible that both of us are related to Charlemagne. I didn't know Charlemagne well, but he did give me a fruitcake for Christmas once.) Evans’s group has reported that some types of biocontainers—notably those made from rice hulls—are highly resistant to crushing. However, none of the biocontainers could match plastic for punch-through resistance.

Biocontainers have not been widely adopted by growers because of concerns about their suitability for ornamental crop production. Koeser and others (2013) looked at the suitability of biocontainers for greenhouse crops. They compared seven types of biocontainer with  plastic containers to see how well they stood up to mechanized filling and transplanting, coleus production, handling and shipping. The plant production part of the study included effects of hand, drip and ebb-and-flow irrigation. Coleus plants grew just as well in the biocontainers as in plastic pots, regardless of irrigation method, but rapid decomposition of biocontainers occurred when subjected to ebb-and-flow irrigation. Bioplastic, wood fiber and straw biocontainers were as resistant to mechanical damage during filling and shipping as plastic pots. Pressed manure and peat pots were particularly susceptible to shipping damage.

Do the environmental benefits of biocontainers make them worthwhile? Koeser and others (2014) recently evaluated the carbon footprint of biocontainer use. They considered all of the material and energy inputs to produce a petunia plant in a greenhouse. In their study, a conventional plastic pot accounted for about 16% of carbon emissions, but another 47% was attributable to lighting and irrigation. The authors concluded that there was a negligible difference in carbon footprint between various biocontainers and plastic pots, and that improving the efficiency of supplemental lighting would be much more likely to reduce the carbon footprint. Good idea!

Richard Evans is UC Cooperative Extension Environmental Horticulturist, Department of Plant Sciences, UC Davis.

References

Beeks SA, Evans MR. 2013. Physical properties of biocontainers used to grow long-term greenhouse crops in an ebb-and-flood irrigation system. HortScience 48: 732-737.

Evans MR, Taylor M, Kuehny J. 2010. Physical properties of biocontainers for greenhouse crops production. HortTechnology 20: 549-555.

Koeser A, Kling G, Miller C, Warnock D. 2014. Compatibility of biocontainers in commercial greenhouse crop production. HortTechnology 23: 149-156.

Koeser AK, Lovell ST, Petri AC, Brumfield RG, Stewart JR. 2014. Biocontainer use in a Petunia ×hybrida greenhouse production system: a cradle-to-gate carbon footprint assessment of secondary impacts. HortScience 49: 265-271.

Yue C, Dennis JH, Behe BK, Hall CR, Campbell BL, Lopez RG. 2011. Investigating consumer preference for organic, local, or sustainable plants. HortScience 46: 610-615.