Improving Transplant Success Of Container-Grown Trees

News reports & helpful tips on tree stump removal.

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!

“Teasing” apart the outer roots is one method of eliminating circling roots.

 

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 base of the tree, they have the potential to girdle the stem and effectively “choke out” the tree.

Nurseries have grown trees in containers for decades, and landscapers have observed container-related root defects for nearly as long. Over the years, researchers have investigated a variety of approaches to mitigating container effects including slicing, butterflying, and teasing apart roots—often with mixed results. More recently, research has shown that shaving—removing the outer periphery of the root systems of container-grown trees—can eliminate circling roots and improve root egress into soils.

Shaving can be done with a pruning saw, reciprocating saw, or sharp spade. In some cases, the container root-ball is cut into a square and is referred to as “box-cutting.” Over the past decade, our lab has conducted research trials on the response of container-0grown trees to an array of pre-plant root modifications. Here we discuss these trials and some of the key implications for landscapers planting container-grown trees.

A Close Shave

In 2012 we installed a trial to investigate the impacts of planting practices on survival and establishment of container-grown Bloodgood London planetrees. Before planting, we divided the trees into three groups and assigned them to three root treatments:

  1. Shaving, in which we removed the outer 1 1/2″ of the periphery of the root system along with the bottom pancake of roots;
  2. Teasing, where we “teased” or pulled apart any circling roots; and
  3. Control, which we planted as-is.

We planted all the trees in landscape test plots at the Michigan State University Horticulture Teaching and Research Center and monitored their survival and growth. We excavated the root systems of a subset of trees two and four years after planting. We found that shaving increased root egress into the surrounding soil and reduced circling roots. Teasing also improved root system quality and increased root egress compared to the control, but not to the same extent as shaving.

This post was originally published here.

I hope you found the above of help and of interest. Similar content can be found on our main site here: https://treesurgeonsc.co.uk/blog
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