August 7, 2012

It's standard: Bottom of trunk flare at grade

Image: Zelkova, no trunk flare

 Two weeks ago, "Dano" left a comment on our post about soils in cities which featured a photograph of a Zelkova that looked to be missing its trunk flare (also known as root flare).  Last month, the American National Standards Institute completed a "major revision to ANSI A300 (part 6)-2012" which now includes a section on tree planting standards.

Image: Correct tree planting dept, ANSI 300 part 6-2012 via TCIA (source)
The standard includes the following information about tree planting depth: "The correct planting depth of a tree is based on locating the trunk flare and being certain that the bottom of the trunk flare is at finish grade upon completion of the operation."  The Zelkova in the first photograph is dying; this tree was a replacement for a Zelkova planted during the fountain renovation.  Someone once told me that Zelkovas do not have a pronounced trunk flare.  If so, then this Zelkova might have been planted too deeply absent the usual visual cue (swelling at base of trunk). Or, the hole could have been dug too deeply.  Or, the root ball settled after planting.

What do you think?  Any Zelkova experts out there?

p.s. Edward Gilman, Dept. of Environmental Hort at the University of Florida has a fantastic Powerpoint about tree root growth after planting.  Also, check out the Dirt Doctor's webpage on root flare management.

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