P&PDL Picture of the Week for
February 18, 2008

Twisted Tale: Tree and shrub installation:
“The roots of trees and shrubs should be disturbed as little as possible at installation.”

Linda Chalker-Scott, Extension Urban Horticulture, Washington State University

Bare-root trees and shrubs are only seasonally available, but have roots that are easily inspected and culled if needed.  Containerized and B&B plants are available year round, but their root systems – and potential flaws - are hidden.  Unfortunately, nursery warranties often stipulate that customers cannot disturb the rootballs of trees and shrubs during installation.  Thus, many structural root flaws remain undiscovered and become more severe the longer they are left uncorrected.  (Figure 1 shows a B&B Cercis that’s been bare-rooted to expose a substantially flawed root system.)

It’s fairly simple to remove the clay from a B&B root ball; it can be more time-consuming to remove soilless media from containerized root systems.  After removing the burlap and twine from a B&B tree, the entire root ball is soaked in water to loosen the clay. Once the clay is removed, the root system is evaluated and correctively pruned, if necessary. Woody roots that are circling, kinked, or curling back underneath the root mass should be removed to create an evenly distributed, horizontally directed, structural root system. For containerized plants, roots are unwounded after soaking and removing media; excessively long roots and structurally flawed woody roots should be removed.  Don’t worry about breaking the fine roots; they are the quickest to regenerate. A pruned root system, once installed, will respond by quickly regenerating new fine roots; it will be important to keep the root zone moist for several months during root establishment.

There are other excellent reasons to bare-root containerized and B&B plant material.
The first reason was discussed earlier:  inclusion of potting mixes or field clay is a form of soil amendment. The soilless media of container plants and clay in B&B specimens bear little resemblance to most urban landscape soils and will impede root movement into the native soil. Instead of planting this foreign material, remove it, and allow the roots immediate contact with the soil on site.  It’s easier to install a bare-rooted specimen, as it’s lighter and requires a smaller planting hole.  And it won’t “collapse,” regardless of fears to the contrary.

Finally, bare-rooting trees and shrubs will allow you to find the root crown.  Too often, B&B trees are burlapped too high on the trunk; unless the burlap and clay are removed, it’s likely that the tree will be planted too deeply.  (Figure 2 depicts a bare-rooted B&B specimen whose root crown was a full 10” below the top of the burlap, indicated by duct tape around the trunk.) The result is a root system that receives too little oxygen, slowing its growth and ability to take up water and nutrients.  Furthermore, the buried trunk tissue is susceptible to disease and pest damage.  Trees buried too deeply may survive, but they won’t thrive and generally require additional fertilizer and pesticide applications.  

Further discussion of these and other “twisted tales” of landscape management are available as free downloadable files on my web page http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/

Click image to enlarge

Figure 1

Figure 2

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service