Costs and benefits of pre-plant root manipulation

Spring has sprung here in Michigan; time to get cracking on lots of projects. One of our new projects is an investigation of pre-plant techniques for dealing with root systems on container grown trees. As many of you know, Linda Chalker-Scott is advocate of bare-rooting trees before planting to correct potential root defects before planting. As some of you may know, I’m skeptical of this approach. It’s not that I think root systems are perfect – far from it. But we lack sufficient information to know whether the costs of bare-rooting (time/effort, stress on the trees) warrant the benefits. We also have little information on how species vary in responding to bare-rooting. From the experience of foresters and bare-root liner nurseries we know that some species are highly sensitive to storage and handling when they’re bare-rooted. When I worked for International Paper, we had little difficulty transplanting sycamores bare-root; whereas we often encountered severe dieback or mortality with sweetgum. Likewise, shade tree nurseries often encounter difficulty establishing oaks, baldcypress, and hackberry from bare-root liners. In fact, J. Frank Schmidt and Sons nursery, one of the largest producers of shade tree liners has discontinued production of bare-root hackberry lines and only produces them as container stock.

As I said, I’m skeptical that putting a tree through the trauma of bare-rooting is worth the potential benefit. But I’m also open-minded and willing to conduct an objective trial to see what’s what. As an aside, I was skeptical about root-shaving before we conducted our own trial and was impressed by the results. For our current study we planted 96 container-grown shade trees last week at the MSU Horticulture Teaching and Research Center. Trees includes three cultivars: ‘Bloodgood’ London planetrees, columnar tulip poplar and ‘October glory’ red maple. We assigned the trees at random to one of four treatments: Control (no root treatment), Shave (outer roots removed before planting) and two bare-root treatments – Bare root – Wash (trees were bare-rooted by washing the roots with water) and Bare root – Airspade (trees were bare-rooted using an airspade). The planting crew consisted of my technician, Dana Ellison; my new Master’s student, Riley Rouse; my undergrad assistants, Becky Pobst and Alex Love; and Linda, who was on-hand to provide quality control on the bare-rooting operations.

For her M.S. project, Riley will be tracking performance of the trees over the next two years. Her measurements will include tree survival and growth as well as measures of physiological responses such as plant water potential and photosynthetic gas exchange. Next fall, after two growing seasons, we will dig a subset of the trees with a tree spade and inspect the root systems to determine the effect of treatments on root system development. In the meantime, here are some photos from last week’s festivities.

 

Right tool for the job. MSU Beaumont Nursery provided a big assist by augering the planting holes.
Tulip poplar roots before shaving
Tulip poplar after shaving
Alex cleans up a planetree with the airspade
Dana’s excited to be washing roots.
Riley washing up a maple – don’t worry the cicling roots come off next…
Light and easy. Becky after airspading a tulip poplar
Wait’ll purchasing sees this… A wading pool is perfect for pre-soaking roots before washing and for storing until planting.
Easy to smile when it’s a Control tree…
Getting a little kinky… Root at the end of the felco’s bending back on itself – corrected after the photo-op.
Looking a little wilty. TheBare-root maples required the greatest root removal and correction
Trial plantation at the end of the planting
Can’t pull off something like this without an awesome crew!

6 thoughts on “Costs and benefits of pre-plant root manipulation”

    1. The holes for the Bare-root trees were augered to half the depth of the holes for the Shave and Control trees. Holes for the bare-root trees were excavated by hand to make them deeper and/or wider as needed. Most of the circling roots such as the ones shown in the picture you referred to were removed. These were woody or semi-woody and would spring back when the trees were mudded in.

      1. Thanks Bert for the explanation. So as I understand it this study Manipulates the soil In the root ball, by either removing it with water or with air or not removing it. It also studies The removal of roots Versus the control.
        If the roots were truly being manipulated, they would be pulled straight , at least The larger Ones that are flexible enough to straighten. It is true that It can be a challenge to prevent them from springing back, but by Taking the time to pack soil around Them After they are straightened, or even to use landscape staples Or rocks to hold them in a radial orientation , This can be done.

        Manipulating roots by Straightening them Can expand soil volume Significantly and immediately. When I plant trees or shrubs, I think it’s a no brainer to at least Try that. In my experience it is worth the extra time and effort. Maybe that would be a harder variable to control For experimental purposes, but would have been worth the trouble. that seems to be a limitation in this experimental model.

        “Manipulation’ means ‘handling in a skillful manner’. This experiment ‘handles’ roots by cutting them off, which frankly does not require a lot of skill, and is not ‘manipulation’. “Pre-planting soil and root removal” would be a lot more accurate, and would not mislead the casual reader, or future reviewers of the literature, into thinking that the roots are actually being manipulated.

        1. Duly noted. I started using ‘root manipulation’ on our earlier study, which included shaving roots or teasing apart and disentangling cirlcing roots.

  1. Please keep us posted! I’ve long hoped to see a large enough set of trees in a controlled setting undergoing different treatments.

    Spring arrived quite a lot ealier in Central Europe this year than it appears to be the case in the US, so I dug out six fruit trees that I planted two years ago to subject them to some gruesome root butchering roughly a month ago. (Only recently I learned about Linda’s approach.)

    I must say I was quite surprised to see how little root they had grown in two years. I was less surprised to see many circling roots.

    The Nashi pear lost almost all of its lush foliage, the other varieties seem to cope better, they weren’t quite so far in their development . The peach is showing some leaf growth again.

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