Root Egress

Cregg and Rouse are involved in a research project at Michigan State University on “Improving transplant success of container-grown landscape trees.” Here are some of the findings they’ve shared with Turf Tree Services. Trees provide a myriad of functions and benefits in landscapes including shading, screening unwanted views, serving as focal points, and even capturing air pollutants and mitigating urban heat island effects. No wonder clients want to plant more of them!   One of the first steps in the tree planting process is deciding on whether to plant ball-and-burlap (B&B) trees or trees grown in containers. Increasingly, landscapers and homeowners are opting for container-grown trees because they weigh less and are easier to handle and plant than conventional B&B trees. However, a major downside to growing trees in containers is the development of circling roots during production. The production of most container-grown shade trees starts with bare-root tree liners (or whips) that are planted in plastic containers, which typically range between 7 and 25 gallons. As roots grow, they eventually encounter the wall of the nursery container, deflect, and begin to circle. Container trees also commonly produce a heavy mat or “pancake” of roots at the container bottom. Both the circling roots around the sides as well as the pancake on the bottom of the root-ball are defects that can limit root egress into surrounding soil after planting. Root egress is essential to successful long-term establishment and for providing tree stability. Moreover, when roots continue to circle around the ...