Five Myths that Plague Urban Forestry Tree Care Advisor Core Course 2012
Myth #1: Deeper is Better
This
versus
This?
Research-Based Evidence that Deeper is Better: ď Ż
Uhhh, there isn’t any.
The Reality:
Deeper, less moisture to roots. Deeper, less oxygen to roots. Deeper, higher frequency of stem girdling roots. Deeper, more confined root system. Deeper, less stability
The Research-Based Evidence
Douglas Airhart – Tennessee Tech U. Bonnie Appleton – VA Tech. Mike Arnold – Texas A & M Susan Day – VPI Donna Fare – U. S. National Arboretum Ed Gilman – U of Florida Christina Wells – Clemson University
Need More?
J. Roger Harris, VPI Gary Watson, Morton Arboretum David Williams and Gary Kling, U of IL T. Davis Sydnor and Richard Rathjens, Ohio State University
What? Even More?
Impact On Storm Damage to Trees?
Most common reason for total failure: Buried SGRs. Species dependent. 1-4 inches. Johnson, 2006. “Storm Damage in Minnesota, 1995-2005.”
Myth #2: Trees Need to be Fertilized
Hmmm, Explain This (that’s volcanic rock, not soil!)
These are Good Reasons to Fertilize: Screens
Not a Good Reason to Fertilize
Good Reason to Fertilize
Phosphorus Deficiency on Plum
Myth #3: The Only Good Mulch is an Organic Mulch
Oh, Good Grief…What Could be Wrong With Mulch?
What’s Good About Mulch?*
Three (3) Inches of Organic Mulch:
Significantly Reduced Weed Pressure Increased Tree Stem Caliper Lowered Soil Temperatures Lowered Soil Oxygen
*Greenly and Rakow, 1995. Effect of Wood Mulch Type and Depth on Weed...
Anything Else Good About Mulch?*
Significantly Reduced Soil Moisture Evaporation Increased Tree Root Length and Density Improved Disease Resistance of Mulched Trees
Faber, Downer, Menge. 2001. Differential Effects of Mulch.
Anything More?*
Enhanced Nutrient Recycling Significantly Increased Fine Root Production Significantly Decreased Harmful Nematodes
Forge, Hogue, Neilsen, Neilsen. 2008. Organic mulches alter nematode commun…
What’s Bad About Mulch?
It’s Like Twinkies
Negative Mulch
Depth:
Too Much, Too Little Moisture Too Much, Too Little Oxygen
Negative Mulch ď Ż
Are Colored Mulches Harmful? ď Ž
No Evidence of any Negative Effects
Negative Mulch
Are Rubber Mulches Harmful?*
Incorporated “crumb rubber” Can Increase Zinc Levels in Some Trees In Some Trees, the Increased Zinc Level can Cause Chlorosis
*Bush, Leader, Owings. 2001. Foliar Accumulation of Zinc in Tree Species Grown in Pine Bark Media Amended with Crumb Rubber.
Crumb Rubber vs. Rubber Mulch
Negative Mulches
Are Mineral Mulches Bad?*
Warmed Soil Earlier in Spring Extended Growing Season Don’t “Condition” Soil Poor Weed Control No Harmful Effects on Trees
* Iles and Dosmann. 1999. Effect of organic and mineral mulches on soil properties and growth of Fairview Flame red maple trees.
Myth #4: Roots are Safe and Out of Sight: The Vision
What is Normal, What is Abnormal
Heart-Root System
Lateral Root System
Shallow Roots Are Vulnerable
Myth #5: Birches and Maples Bleed in the Spring...So Don’t Prune Them!
“Sapping” Trees?
Does it Help to Paint?