UMASS/UNH Grow Bag Study
Beginning in 2010, the Univ of Massachusetts and Univ of New Hampshire conducted a 3 year study of grow bags in comparison to B&B and PIP at Amherst Nurseries and the University of New Hampshire farm.
Three hundred trees were planted at each site, with 100 each of swamp white oak, crabapple, and river birch. The plots were fertilized, irrigated, and pruned under commercial nursery production methods. At the end of the study, the trees were harvested and examined for overall growth comparison and root structure. The root structure comparison was extremely time consuming and very thoroughly completed - an unusual undertaking due to the time involved. The results were interesting.
Root system results were as follows:
- B&B had minimal root defects, and most roots were large because the fine roots had been severed and remained in the field
- PIP had significant and widespread root defects (despite being treated with Spin Out to reduce circling roots), and most roots were fine creating a very dense root ball
- Grow bags did not circle and often had nodes against the sides or bottoms rather than circling. A good mix of fine and large roots, and more medium sized roots than B&B or PIP
Economically, grow bags were found to have the lowest overall production costs, followed by B&B and PIP.
Results have been published in American Nurseryman magazine in July 2014 (examines the three different growing systems) and August 2014 (examines the economics of the three systems).
Video of the UMASS/UNH study at the beginning of the process can be viewed here
Video of the UMASS/UNH study at the mid-point of the process (during year 2) can be viewed here