Some interesting research has been published by Michegan State Uni on pulp cardboard plant pots versus traditional black plastic.
Tom Fernandez led a team of researchers from Kentucky, Texas and Mississippi in evaluating the pulp pots as a replacement for plastic, looking at pot longevity and any growth differences in standard container-grown stock of Euonymus fortunei ‘Roemertwo’ (Gold Splash).
Containers were placed on the ground and measurements taken of mortality, plant height and other growth indices.
While both pot types lasted through the season without significant deterioration and there was little difference in plant growth, plant deaths were only 2% in pulp pots but 13% in plastic during the summer growing season. Researchers propose that plants were more heat stressed in the plastic pots but also found that those in pulp had higher water demands.
However, during winter the survival rates reversed dramatically, with a 52% death rate for pulp pot stock and only 15% in the plastic. As the pots were kept in an unirrigated area during the winter, evaporation from the sides of the more porous pulp containers created severe water stress in the pulp pots.