by John Kinchla
Amherst Nurseries grows trees and shrubs on approximately 100 acres of land on farms in Amherst, MA and Charlemont, MA. As the nursery owner, I try to produce plants that are as environmentally friendly as possible by reducing the use of pesticides, using drip irrigation, and growing in field soil (which uses less water and fertilizer than plastic container methods). One problem with field grown nursery stock is the loss of soil when the plant is harvested balled and burlapped (B&B). Since the soils at Amherst Nurseries are of a very high quality, the problem of soil loss is something that I’m acutely aware of. In response, I’ve been shifting the production of Amherst Nurseries from B&B to grow bags as a means to reduce the loss of field soil via B&B production.
Beginning about 10 years ago, Amherst Nurseries started to grow trees in grow bags because the volume of soil contained in the bag was much smaller than the soil that would be consumed using B&B methods. The bags are manufactured by Rootmaker® Products (www.rootmaker.com) and High Caliper™ Growing Systems (www.treebag.com), and they are designed to eliminate root circling typical to other containers, while encouraging a dense root system within the bag. While in use for growing stock at the nursery, the bags are filled with field soil and planted in the ground; the tree is then planted and grown inside the bag. When the tree is harvested, most of the root system is retained in the bag, which means more energy is available to the tree upon transplanting into the landscape. The intact root system greatly reduces transplant shock and allows for trees to establish faster in the landscape than is typical with B&B.
From Soil to Mix
After a few years of using grow bags filled with field soil, I decided to completely eliminate the loss of field soil by substituting a compost/bark growing mix for field soil inside the grow bag. This change provided the trees with a nutrient rich media, and resulted in bags that weighed less than the bags filled with field soil. With this change, Amherst Nurseries reduced fertilizer usage, labor, and freight while producing a superior product. Customers liked the lighter weight trees because they greatly reduced labor and equipment needs on job sites, the trees also still established quickly and had no circling roots. Furthermore, shipping and handling is much easier because load/unload times are quicker, due to the lighter weight of the bags. Also, at least twice as many trees grown in bags will fit on a trailer compared to B&B trees, and the whole load weighs less.
The University of Massachusetts and University of New Hampshire recently concluded a four-year study that compared B&B, grow bag, and plastic container grown trees. Amherst Nurseries was one of the research locations where the trees were grown. Preliminary results indicate that soil loss growing 2-inch caliper trees B&B is about 65-80 tons per acre, or about five large dump-truck loads of soil. In addition, grow bag trees were shown to weigh about 65% less than B&B trees of the same size. Trees that were grown in plastic containers consistently had significant root circling, despite the fact that they were treated with copper hydroxide to eliminate root circling. Trees grown in grow bags had little to no root circling and a robust, dense root system. Overall, the study indicates that trees grown in grow bags minimize soil loss, reduce irrigation needs, encourage better long term-tree health by ensuring a larger root surface area without circling, and reduce the carbon footprint of the plant through increased freight efficiency.
From Experimental to Expanded Use
Due to the many benefits of grow bags and positive feedback from customers, Amherst Nurseries will continue to expand its offerings of trees grown in grow bags to include sizes from 1-inch to 4-inch caliper. Amherst Nurseries also grows a limited number of shrubs in grow bags, and plans to increase those offerings as well. If you would like more information on Amherst Nurseries, please visit the website at www.amherstnurseries.com and view the full offerings at www.amherstnurseries.com/cat.
About the Author
John Kinchla owns and operates Amherst Nurseries in western Massachusetts. He may be reached at firstname.lastname@example.org.