Volcano mulching

Just visiting the local grocery store makes me grimace. It’s all about the trees there. Last year, landscape and lawn care companies tidied up borders, trimmed and pruned shrubs at the grocery and then they piled at least a foot thick layer of mulch against the trunk of all the trees around the parking lot, a process that has been dubbed ‘volcanoes,’ or ‘turtle mounds.’

mulch volcanoes 1/13/2019

volcanoes January 2019

I’m always amazed to see a sight like this. For decades, arborists and extension experts have railed against such practices because it will sentence a tree to a slow death. Why we still see everywhere it is a mystery to me.

Not only commercial sites, but old trees and new trees in neighborhoods within a mile of my home are mulched with volcanoes. The mulch volcanoes have settled over the fall and winter months, but still piled high against the bark.


volcano mulch 1/13/19

Mulch done right is beneficial for a tree. It prevents weed growth, protects bark from a weed wacker, helps retain moisture, and helps to moderate soil temperatures in all seasons. But the volcano mulch piled against the bark of tree, especially young trees, will soften the bark and invite the invasion of rodents, insects, fungus, rot and the suffocation of the trees’ roots.

I’ve been taught to think ‘doughnut’ when mulching a tree and limit the mulch to two, three or four inches deep… max. Once I apply, I pull the mulch away from the trunk for about five or six inches until the root flair is visible.

It’s a puzzle to me why volcanoes are so popular. Is it that the professionals don’t know better or do their clients prefer the volcano look? It frustrates me and as a frustrated Charlie Brown would say, “Aaugh!”


15 thoughts on “Volcano mulching

  1. Oh my! that would be a good topic for my ‘Horridcultlure’ on Wednesday. We do not see it as commonly here just because ‘gardeners’ are too dang lazy to mulch. I remember seeing it in Western Washington and Oregon though.

    Liked by 1 person

  2. Hi Annie. I see this practice all the time and it really winds me up. I hope you don’t mind if I use your comment section to rant a bit. You might find it of interest though because I think I can offer some insight into why this phenomenon refuses to die even though the information about how destructive it is and what a waste of money and resources it amounts to is freely available in the public domain.

    I’ve noticed a pattern to where mulch volcanoes tend to show up most frequently and in the greatest numbers. Those places are: commercial properties, common spaces owned by homeowners associations, and properties – particularly verges between sidewalks and roadways in residential neighbourhoods – that are owned by local governments.

    These kinds of places have a few things in common. Firstly, they are owned by lots of individuals through an “entity”. This means that no single individual has a strong claim to ownership or a correspondingly strong sense of responsibility toward of any of the trees in these landscapes.

    Secondly, these landscapes are similar in that they are not maintained directly by any of the individuals belonging to the entity that exercises direct ownership over them. Instead, individuals’ financial resources are pooled together and paid out to a landscaping company, who acts as an agent contracted to maintain the property on behalf of the “principals”- the hiring entity and its constituent members. In the same way that individual’s claim to ownership over and sense of responsibility toward the trees and other assets in these kinds of landscapes is because of the distributed ownership structure, because any given individual’s direct contribution toward the landscape’s maintenance is likely to be small, the individual’s sense of having a financial stake in the condition of these landscapes is usually correspondingly small. This effect is especially evident when individuals may be upset at how the landscape (or other commonly owned assets) are being maintained, but they remain insufficiently motivated to do anything about it. This is because they implicitly just that the personal cost to themselves of affecting a change, in terms of time and effort, is far greater than the current costs being imposed on them by the status quo, so unhappy thought they maybe, they choose to accept the status quo.

    All this has been to say that I think the reason mulch volcanoes are so commonplace is because of a phenomenon in economics called the “principle-agent problem”, which wikipedia describes nicely:


    “Common examples of this relationship include corporate management (agent) and shareholders (principal), elected officials (agent) and citizens (principal), or brokers (agent) and markets (buyers and sellers, principals)…

    “The problem arises where the two parties have different interests and asymmetric information (the agent having more information), such that the principal cannot directly ensure that the agent is always acting in their (the principal’s) best interest,[3] particularly when activities that are useful to the principal are costly to the agent, and where elements of what the agent does are costly for the principal to observe (see moral hazard and conflict of interest)…

    “The agency problem can be intensified when an agent acts on behalf of multiple principals (see multiple principal problem).[4] When one agent acts on behalf of multiple principals, the multiple principals have to agree on the agent’s objectives, but face a collective action problem in governance, as individual principals may lobby the agent or otherwise act in their individual interests rather than in the collective interest of all principals.[5] As a result, there may be free-riding in steering and monitoring,[6] duplicate steering and monitoring,[7] or conflict between principals,[8] all leading to high autonomy for the agent. This has been coined the multiple principal problem and is a serious problem particularly in the public sector, where multiple principals are common and both efficiency and democratic accountability are undermined in the absence of salient governance.[4][9][10] Examples of organizations in which this problem may occur are in the governance of the executive power, ministries, agencies, intermunicipal cooperation, public-private partnerships, and firms with multiple shareholders.[4]”

    All the conditions are present for the agents – the landscapers – to behave in a way that is consistent with pursuing their own interest – maximizing their revenue – in ways that are antithetical to the principals’ interests. The principals, as noted, do not individually have a strong ownership claim over the landscape or its assets, and they don’t have a large financial stake in the particularls of how it is maintained. They also tend not to know much about landscaping or what constitutes proper care of landscape plants. These factors mean that the principals tend not to pay close attention to what the agents charged with maintaining them do, and that they wouldn’t be able to evaluate how well the agents were fulfilling their contractual obligations in any event. This introduces the problem of asymmetric information – the agents know more about what they’re doing and why than the principles, which gives them leeway to behave in a way that benefits them at the expense of the principals’ welfare wihout the principals recognizing this fact. To put it in plainer language, the landscapers are able to take advantage of the fact that the principals they work for don’t know what the landscapers are up to, aren’t able to evaluate how well they’re doing their jobs, and they aren’t terribly inclined to care, or at least feel sufficiently motivated to take action if they feel dissatisfied.

    I don’t think landscapers keep making these mulch volcanoes because they’re too dumb and ignorant to know better. I think they do this to trees because it kills them, and it does so slowly in a multi-stage process that provides the landscapers with opportunities to generate more revenue than they’d generate otherwise. To spell it out, the landscapers generate revenue selling the labour and the mulch, then when the mulch starts causing the trees stress-related health problems, they generate more revenue selling the principals things like “tree spraying” to control the secondary symptoms of the problems they’ve caused. Next, when the trees finally die, the landscapers generate more revenue cutting them down and removing them, and then they generate still more revenue selling the principals replacement trees, along with a new heap of mulch to go with it and the labour needed to get the cycle started all over again.

    I wouldn’t underestimate how useful killing trees this way is to landscapers. Mulch volcanoes kill slowly and indirectly, both of work to their advantage. The former is an advantage because the tree’s death and the ultimate cause are usually separate in time by many many years, making it unlikely that casual observers will link the landscapers’ actions with the trees’ deaths. The latter is advantageous because the proximate cause of death when the trees do finally die is always something else, like drought, insect infestation, fungal infection or something like that. The fact that trees won’t all die at once even of they’ve had their trunks buried in rotting wood chips for the same length of time is also an advantage, because people will see trees living their lives in the center of a mulch volcano apparently without problem for years, so they won’t be inclined to attribute that mulch volcano to the tree’s eventual decline and death when it finally happens.

    I also wouldn’t underestimate how simply nudging the annual mortality of the population of trees “maintained” by a landscaping company can generate a meaningful source of extra revenue for them. This becomes especially clear when you consider that a given landscaping company can easily have tens of thousands of trees under its care. When the annual tree mortality rate rises as a result of tree overmulching from something like 0.05% to 2%, for a landscaping company that oversees 10,000 landscaping trees, the number of dead ones the company will have opportunity to be paid to remove and replace rises from 5 to 200. Given the $650 national average cost to remove a dead tree, that amounts to an extra $130,000/year in revenue.

    So that mortality rate increase represents a meaningful uptick in business, but it’s still low enough that it takes 50 years on average to turn over the entire population of trees. That’s a long enough turnover period that few who weren’t looking for overt signs of malpractice would notice unless they knew specifically what they were looking for.

    I live for part of the year in the UK, and what I’ve found interesting is that in the UK, landscapers don’t have this practice of generating extra revenue by killing trees slowly with mulch volcanoes. They do generate extra revenue – in exactly these situations where there are principal-agent problems – by killing trees slowly. Over there, they do this by topping mature trees (in other words, cutting all the large branches, including all leaf-producing parts of the trees so that they look like gigantic hat racks). Landscapers sell city council these services by claiming it prevents the possibility trees losing large branches or collapsing onto streets and homes where they could do harm. In reality, the practice, which is an an arboricultural cardinal sin, sets in motion a number of problems that necessitate lots of follow-up care – which of course the landscapers are all too willing to sell – and that ultimately eventually result in the premature death of the tree.

    Be cynical about this practice. It relies on deceiving people in order to steal their money, and it results in the destruction of people’s property.

    Ok, rant over.


    • Great “rant.” It upsets me whenever I see this practice. Our own neighborhood association hires a company (with a first rate reputation) that volcano mulches. Sigh…


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