Is plastic better than pulp containers for nursery plants?

Recent research sheds some preliminary results on the issue of pulp versus plastic nursery pots. Plant growth and mortality were measured in the trials.

Recent research conducted by Michigan State University Extension specialist Tom Fernandez from the MSU Department of Horticulture evaluated the possibility that pulp-based containers could be a replacement for plastic nursery pots. He is part of a team of researchers from the states of Kentucky, Mississippi, and Texas that have been working on a USDA Specialty Crop Research Initiative project to evaluate the alternative pot options. There is quite a bit of concern over the adaption of pulp-based containers regarding whether they can stand up to the production and shipping rigors in a nursery. We know that the market demand for a more sustainable container is increasing by the end consumer.

The study evaluated two factors, the first being if there was any growth differences in Euonymus fortunei ‘Roemertwo’ (Gold Splash) grown in 1 gallon containers on the ground that were either pulp-based (Photo 1) or plastic. Plant height, growth index and mortality were measured from June through October 2011 at the MSU Horticulture Research Farm in East Lansing, Mich.

Fiber pots
Photo 1. Fiber pot plants in test plot. Photo credit: Tom Fernandez, MSU

There were no significant differences in plant height or growth index between the plastic or pulp containers (Photo 2.) The plant mortality during the growing season was 13 percent in plastic containers and 2 percent in the pulp-based container. This indicates plant stress may be reduced when using pulp pots above ground. However, water use was higher in the pulp containers and overwinter mortality increased to 52 percent for the pulp-based containers and 15 percent for plastic. This was likely due to containers being overwintered in unirrigated hoophouses and higher evaporation from the side walls of the pulp containers, leading to greater moisture stress.

Plastic and fiber pots
Photo 2. Plastic pot on left, fiber pot in center and right. Photo credit: Tom Fernandez, MSU

Container durability was very good for one growing season; longer duration testing was not done and these pulp containers were not designed to perform for more than one year.

Dr. Fernandez’s work is funded in part by MSU’s AgBioResearch.

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