Root Collar Examination
Tree Care 101

Best Reference!
A Practitioner's Guide to Stem Girdling Roots of Trees (University of Minnesota Extension)
 

Images of root collar examinations in the BRCC Arboretum:

Images from trees on campus:

Images from mature trees:

Landscape Fabric - AVOID!

 

 Do you need to perform a root collar examination on your trees?  
YES! Before getting too attached to a tree - check out the tree's root collar. With the exception of some evergreens, nearly all trees have a flare, or bulging area, where the tree trunk meets the soil. What's that you say? You can't see the root collar because mulch is piled up against the trunk? Well, that's your first problem. Go to the mulch page for information about proper mulching techniques. Now that you have a clear view of the root collar look for the flare. If the root flare is absent begin to assemble the proper tools and set aside about 30 - 60 minutes to conduct a proper root collar examination. 

Is there a problem if I don't see a root flare? 
Yes! Your tree is either planted too deep, or the roots are girdling the trunk, or both. Better start to detach yourself from this tree. Depending upon the age and health of the tree (and you) there may be some remedial steps you can try. If the tree is planted too deep the roots will be lacking oxygen and will usually attempt to grow to the surface. If drainage is a problem in this area the roots will be more susceptible to root diseases. Steps need to be taken immediately to correct this situation. If the tree roots are girdling the trunk your tree will slowly strangle itself to death, that is if it doesn't first fall over.  

How could I have planted it too deep? Maybe you didn't! There are several opportunities for nursery operations to "plant" the young tree too deep in pots. This usually occurs when the plants are moved into increasingly larger pots. Plants in the field may have soil piled over their root system and against the trunk during cultivation of the fields or when preparing the tree for being balled & burlaped. Click here (Nursery) for images of girdling roots that I've encountered recently.

I think most arborists agree that more trees are being buried  - not planted. In the past, folks would make two critical errors: first, they would dig a hole considerably deeper then needed; second, they would amend the soil with organic matter (i.e. peat moss). These two conditions cause recently planted trees to settle into the ground, well below the original soil profile. Current planting recommendations consist of digging a shallow hole (just deep enough for the root ball) and not amending the soil with organic matter. If you simply have to amend the soil, then amend the entire area where the roots will grow in the future (i.e. entire bed or the entire yard). 

Is there anything I can see above ground indicating that a tree may have a girdling root? 

  • Absence of a root flare.
  • The lower trunk may appear to be fluted and large buttress roots can be seen twisting around the base of the tree. 
  • One of the most obvious, and dangerous, symptoms would be that the tree is leaning. 
  • The tree appears to be sickly, in particular it would have a thinning crown and stunted growth compared to other trees.