Topic: What follows, is a discussion of the all too common practice of an over-application of mulch, usually shredded bark, as well as faulty application techniques.
My Rant: This is an unashamed, full-blown rant against an on-going horticultural problem. This is NOT meant to alienate or disenfranchise fellow home gardeners or true professional gardeners (for most of whom this is widely-known, repetitive information). In fact, it is my hope that new gardeners, mistakenly subscribing to this erroneous practice, will change their modus operandi.
After pulling out my virtual soapbox, for the past twenty years (with my radio & TV programs, a newspaper column, horticultural classes, lectures, etc. at my disposal, I have taken every opportunity to "spread the word" - as have so many others), I see little, if any, improvement. In fact, this year seems worse than usual... the mounds are higher and even more widespread... homes, malls, storefronts, professional buildings, parks and even some street plantings are proudly exhibiting these gravity-defying mulch mounds some, extending 1-2' high up the trunks of trees, both young and old. So, many city and town municipalities are joining in this practice, as well, often with devastating results to the plants they seek to showcase and protect.
Benefits of Mulch: Shredded bark, bark chips, finished compost, peat and buckwheat hulls are just some of the materials with which we mulch our landscape. We mimic nature and what happens naturally in field and forest, as an accumulation of dead plants and leaf litter covers the soil, retarding the growth of some undesirable plants, and breaks down to nourish established plants and conserve moisture. Our mulch of choice provides the same advantages, for our suburban landscapes. Our final decision is based as much on practicality (wind and topography are determining factors), as well as the aesthetics a well-chosen mulch brings to our finished landscape... color and texture are key, as we choose that last component, to showcase and highlight our cherished plant collection... providing a final unifying element to the finished landscape.
Generally Accepted Premise: When mulching flower beds, 1-2" of mulch is sufficient... for trees and shrubs, a 2-3" layer will suffice (certainly not more than 4"). From the tiniest annual to the mightiest oak, there is one common rule of thumb - you never, ever want the mulch to remain in contact with the crown, stems or trunk of any plant. There should remain an area, at the base of any mulched plant, absolutely mulch-free. In fact, the base of a tree trunk should be surrounded by a circle of 3-4" of bare soil, to avoid the possibility of contact.
All plants have surface roots, requiring oxygen. When you apply a deep, heavy, wet layer of mulch, you prevent this healthy exchange. Since the the surface roots are never allowed to dry slightly, and deeper roots are constantly wet, you are likely to encounter the ill effects of over-watering, especially in heavy or poorly-drained soils. This provides the ideal playground for such disease as Phytophthora, which is an opportunistic, root-rotting pathogen.
It is a well-known fact that tree trunks, once girdled completely, can no longer conduct moisture and nutrients upward or go through all their processes, including photosynthesis, so death ensues. Rodents and deer are often responsible for such damage and once girdled, a tree succumbs fairly quickly. Not so, with the dreaded mulch mound. This is an often long, drawn-out process, especially on older trees with a dense bark layer.
Who's responsible?: In a search to determine the genesis (or the one "genius" who started all this, so we can go to the source and stop the madness!) behind the mulch mound movement, I decided to start with something as basic as word definitions... to deconstruct the theory behind the practice. Now, this is a bit tongue-in-cheek, but hits the mark, nonetheless.
From the online dictionary, definitions relevant to this particular discussion [bracketed sarcasms will lead you along through my own logic chain, as we investigate this ongoing tale of horticultural horror, perpetuated by certain "landscape professionals"] ...
A material (such as decaying leaves, bark or compost) spread around or over a plant to enrich or insulate the soil ["around or over a plant" - is this where the logic train becomes derailed? Perhaps they read "over" literally!]
• an application of such material: regular mulches keep down annual weeds.
• a formless mass or pulp [what eventually happens to the the over-mulched victim] : a mulch of sodden brown stems.
apply a mulch
•treat or cover with mulch [again, are they reading "cover" literally?]
a rounded mass projecting above a surface [and projecting 1-2' up the tree trunk, rotting the bark and leaving entry points for insects and disease!]
•a raised mass of earth, stones or other compacted material, sometimes created artificially for purposes of defense or burial. [Ironically, "burial" seems an appropriate term, for the purpose of this discussion!]
•a small hill
•(a mound of/mounds of) a large pile or quantity of something: burying potential problems under mounds of cash [how about causing potential problems under mounds of mulch? Ironically, the vigorous over-application of mulch eventually becomes what can only be considered as a burial mound.]
heap up into a rounded pile : mound the pie filling slightly in the center. [These folks have taken "heap up" to a whole new level, when it comes to mulch... almost an art form, as if there were some hideous competition to see who can mound mulch the highest up the tree trunk, defying all logic, commonsense cultural practices and laws of gravity.]
• the hospital carried out a postmortem autopsy, postmortem examination, necropsy. [What an arborist or garden center professional will be conducting, after the unfortunate demise of an over-mulched specimen... also what I just conducted on the stumps of Kwanzan cherry trees, which expired over the course of ten years. The city park department (city shall remain nameless ~ not a Cape Ann town) just cut down the last two dead trees. Girdled, with rotted bark, armillaria root rot and borer infestation were what I found... sadly, I am unsurprised. It was about what I expected. And this mulch was only maintained at about one foot up the trunk!]
a box or crate used as a makeshift stand by a public speaker : [as adj. ] a soapbox orator.
• figurative a thing that provides an opportunity for someone to air their views publicly [What I proudly mount, on a somewhat regular basis, to air my views about the hideous, dangerous mulch mounds that surround us!]
Who knows? Perhaps the originator of mulch mounds will read this and forever change his mulching methods... well, I can dream, can't I? Anyway, feel free to join me in this rant. While you're out there, spreading mulch in your yard today, spread the word, would you?
©Deb Lambert 2008
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