#root flare

Tree care #2

These are some very satisfying examples of Root Flare on trees; they look great, they are healthy, and this is exactly how all trees flares should look like. If you see a big tree coming straight up from the ground, with no root flare showing, like this:

then know that this tree is planted too deep, it’s root flare is not getting the air exposure and oxygen it needs; this tree will get very sick and won’t be able to live as long. 

Root flares are supposed to be above the ground level, these are not roots, they need to be kept dry, not covered in soil or mulch, or they’re susceptible to rot. Once the tree starts rotting, she can still stay alive, but unhealthy. However, these trees can be saved! There are teams going on missions to dig out the root flare, and this will help the tree to gain back health. Not enough people do that tho, so if you see a big tree without any root flare showing, consider getting your hands dirty and digging around to see if there’s any flare you can free up. Your tree will love you and look beautiful and healthy. Healthy trees can live forever.

Source (click to watch a video of more examples and explanations, male narration tho)

Look at those trees. I was staring at them today and I honestly can't tell what their deal is. They might even be just one tree, that at some point fell down, and then decided, eh this works too, and just kept growing. Because what tree would intentionally grow like this? But then the one in the background is just the same, half-horizontal, half-tree.

I feel like it might be related to the area they're growing on; this place gets heavily flooded, and it's all mud and clay, so I assume the roots and trunks got unstabilized due to waterflow, then figured out a way to keep still when the flood comes – by simply having the tree lie down.

Look at that trunk flare tho! All the tips of roots are visible above the soil, they look so cool, and this is actually a great thing. All trees should have the root flare visible, because this part of the tree is supposed to be above the soil level, and it needs exposure to oxygen, it could easily rot if trapped underground. When you see a tree that just starts vertically with no roots visible, that is a tree that will get sick if not helped.

I can't tell how these will do but I love them very much, they are coping, and other people love them too. Those pieces of wood you see in the front—that's a table, the flood water took away the top plank. People like to come and have a picnic there! Here's a bonus pic of how this place looks in the summer.

1: Correct planting trees:

2. Correct pruning:

3. Trunk Flare exposure (trunk flare is the part between the bark and the roots!)

Two trees, planted at the same time in similar yards. Both get mulched each spring. Both look identical above ground for the first several years. Fifteen years later, one is still growing vigorously with a full, healthy crown. The other is in slow decline, with thinning foliage, tip dieback, and bark abnormalities at the base that a professional arborist will eventually identify as root collar rot caused by long-term root flare burial.

The only difference, from year one, was how the mulch was applied.

This comparison is not hypothetical. It describes a pattern that plays out in residential landscapes throughout Monmouth County and the rest of New Jersey constantly - and it illustrates why the details of how something is done matter as much as whether it is done at all.

What a Correctly Mulched Tree Looks Like

Correct mulching creates a flat ring of organic material around the base of the tree, extending outward toward and beyond the drip line if possible, with a pronounced clear gap between the edge of the mulch and the trunk bark. The mulch ring should be two to four inches deep throughout - deep enough to moderate soil temperature, retain moisture, and suppress competing vegetation, but not so deep that oxygen exchange into the root zone is impaired.

The critical element is the gap at the trunk base. The mulch should never touch the bark. There should be a visible few inches of open ground - or near-ground - between where the mulch starts and where the trunk base is. This gap allows the root flare zone, the biological transition zone where trunk meets root system, to receive air exposure, dry between rain events, and function as the aerial-adapted tissue it actually is.

A correctly mulched tree benefits from all the recognized advantages of mulching: moderated soil temperatures in both summer heat and winter cold, reduced water evaporation from the soil surface, suppression of grass competition that would otherwise draw water and nutrients away from tree roots, and improved soil structure as the organic material decomposes. Done correctly, regular mulching is one of the better things you can do for an established tree.

What a Mulch Volcano Looks Like

A mulch volcano is the pattern in which mulch is mounded against the trunk in a cone shape. The mulch rings the base of the tree not as a flat layer but as an elevated pile, often four to eight inches deep directly at the trunk and tapering outward. In many cases, the mound gets taller each year as fresh mulch is added on top of the previous year's layer without pulling back the material that has decomposed and compacted directly against the bark.

Visually, the mulch volcano has a tidy, intentional look that homeowners and landscapers often find appealing. It gives the base of the tree a clean, framed appearance. This is part of why the pattern is so widespread - it looks like it was done carefully.

The problem is entirely underground and out of sight.

What the Mulch Volcano Does to the Root Flare Zone

The root flare - the zone where the trunk transitions to the root system - is adapted to aerial conditions. The bark tissue in that zone needs to be able to dry between rain events, exchange oxygen with the atmosphere, and exist in a moisture environment that cycles rather than remains persistently saturated.

A mulch volcano holds the root flare zone in continuous contact with moist, decomposing organic material. Decomposing mulch retains water efficiently - that is part of what makes mulch useful as a soil cover. But when that moisture-retaining material is pressed directly against the trunk bark, the root flare zone stays wet between rains in a way it was not designed for.

The consequences develop through a sequence. Continuous moisture at the root flare reduces the oxygen available to the bark cells in that zone. Bark under anaerobic conditions loses its normal tissue integrity over time. Opportunistic pathogens - particularly the Phytophthora water molds that are endemic in most temperate soils - find the conditions they need to establish and spread into weakened bark. Once collar rot of this type begins, it can work its way around the circumference of the trunk base, eventually girdling the tree by destroying the vascular tissue at the crown.

The other mechanism the mulch volcano activates is girdling root development. Roots that cannot spread outward normally at the correct soil level sometimes redirect and grow in circles around the trunk. These girdling roots constrict the vascular tissue as both trunk and root expand in diameter over years. Small girdling roots can sometimes be removed during root collar excavation. Large ones that have fused with the trunk are much more difficult to address.

The Arbor Day Foundation at arborday.org specifically addresses mulch volcano application as a harmful practice in its guidance for homeowners, noting that it is one of the most preventable causes of landscape tree decline in residential settings.

The Timeline Comparison

This is where the comparison becomes most striking. The mulch volcano applied this spring looks harmless. The correctly mulched tree looks almost identical. Nothing visible distinguishes the two for years.

The mulch volcano tree begins its underground damage accumulation within the first one to two seasons of mounding mulch against the bark. Anaerobic conditions at the root flare zone begin immediately. Pathogen establishment follows as the bark defense capacity weakens.

The correctly mulched tree accumulates none of these conditions. Its root flare zone cycles normally with weather. Its bark defenses at the trunk base remain intact.

For the first five years, both trees may show identical above-ground growth. From years five to ten, subtle differences may begin to appear: slightly smaller leaf size on the mulch volcano tree, slightly earlier fall color, minor tip dieback in the outer crown. These are easy to attribute to drought or other causes without examining the trunk base.

From years ten to twenty, the divergence becomes pronounced. The correctly mulched tree continues growing without issue. The mulch volcano tree shows progressive crown thinning, bark abnormalities at the base, possible weeping or fungal growth near the trunk. By the time a professional is called to evaluate what is happening, the accumulated damage is often significant.

Rutgers Cooperative Extension at njaes.rutgers.edu has documented this type of delayed decline in landscape tree health evaluations, identifying mulch volcano application as a contributing or primary factor in a substantial portion of root collar rot cases they review.

The Simple Fix

Correct mulching takes no more effort than incorrect mulching. It requires only a different spatial pattern. Apply mulch outward from the tree, keep it flat at two to four inches, and maintain a clear gap between the mulch edge and the trunk. Never pile mulch against the bark. Never add a fresh layer on top of old mulch that has already compacted against the trunk without first pulling the old material away and starting fresh.

If you already have mulch volcanoes around established trees, pull the material back from the trunk bases immediately. Expose the root flare zone to air. Check the bark where the mulch was in contact - if it looks healthy and firm, you caught it in time. If the bark in that zone looks soft, dark, or cracked, it warrants an arborist evaluation.

In Monmouth County, both Hufnagel Tree and Middletown Tree Service offer root collar assessments for properties with concerns about buried root flare. The window for effective intervention is widest when damage is still limited, and pulling back a mulch volcano is the fastest way to know whether you are still in that window or whether the bark damage has already advanced to the point where professional excavation and assessment are needed.

There is a tree problem I have been seeing in yards around Monmouth County for years, and it almost never gets recognized until the tree is already in serious trouble. It does not announce itself. It does not look like anything is happening at all. And because the consequences play out over ten or fifteen years rather than one or two, most people never connect the cause to the outcome.

The problem is buried root flare. The cause is usually something done with good intentions - mulching around the base, adding topsoil, regrading the lawn. The result, over time, is a mature tree that slowly loses its ability to function from the base up.

What Root Flare Is and Why It Being Buried Matters

The root flare - the zone at the base of the trunk where the stem widens and transitions to the root system - is designed to be exposed to air. The bark tissue in that zone is fundamentally different from root bark. It requires oxygen exchange, moderate moisture cycling, and the ability to dry out between rain events. It is not designed to be in continuous contact with wet soil or compacted organic material.

When that zone gets buried, a few things happen. Oxygen diffusion into the bark tissue drops. The moisture level in the buried bark stays elevated persistently. Pathogenic fungi that are present in most soils, but held in check under normal conditions, find exactly the environment they need to establish and spread. And the roots, unable to spread outward at the correct level, sometimes begin growing in circles around the trunk base, creating girdling roots that constrict the vascular tissue as both trunk and root grow in diameter over years.

None of this happens quickly. That is the whole problem. A large, established tree has enough reserves to keep looking completely healthy for years while the damage accumulates underground. By the time the canopy shows thinning, dieback at branch tips, or bark abnormalities at the base, the process has often been running for a decade or more.

How It Happens in Normal Monmouth County Yards

I have walked through a lot of properties in this county over the years, and the same scenario plays out constantly.

A family plants a tree, or buys a property with established trees. They hire a landscaper who mulches everything each spring. The mulch gets applied in rings around the trees, and each year the crew mounds it slightly against the trunk because it looks cleaner that way. After a few years, there is a six-inch mound of decomposed organic material directly against the bark. That mound has been keeping the root flare zone continuously moist for years.

Or a yard gets regraded for a patio and a few inches of fill soil end up against several tree bases. Or someone adds topsoil to establish a lawn and the grade rises around the trees. Or the nursery tree that went in fifteen years ago was already planted two inches too deep when it came off the truck and nobody noticed.

None of these feel like harmful decisions at the time. Mulching is supposed to be good for trees. Regrading a patio is normal property maintenance. The problem is the cumulative effect on the root flare zone over years.

What You Can Check Yourself

The simplest thing to look for is the shape of the trunk at the base. A properly positioned root flare is visible as a pronounced outward widening of the trunk as it approaches the ground - the tree should splay outward noticeably as it meets the soil. If the trunk base looks like a straight cylinder going into the ground, like a telephone pole, the root flare may be buried.

Also look at the mulch around your trees. Any mulch touching the trunk bark is a concern. Mulch mounded in a cone shape against the trunk - the classic mulch volcano pattern - is a direct indicator of buried root flare conditions.

If the base of a tree shows any of these: soft or sunken bark at the soil line, bark that is weeping dark sap, fungal growth near the base, or roots arcing over the soil surface and re-entering it - those are signs that damage may already be underway.

Rutgers Cooperative Extension at njaes.rutgers.edu has resources on recognizing root system disorders in residential trees, including the relationship between planting conditions and the development of root collar disease. Their extension publications are worth reviewing if you want to understand what healthy root collar conditions look like versus what the warning signs are.

What Can Be Done

If the problem is just mulch, the fix is immediate: pull the mulch back from the trunk so there is a clear gap of several inches between any mulch and the bark. Keep mulch in a flat ring extending outward, not a mound against the trunk. This is something any homeowner can do today.

If fill soil is involved, professional root collar excavation with an air spade - a pneumatic tool that moves soil without cutting roots - is the appropriate approach. An arborist doing this work exposes the root flare, assesses the condition of the buried bark, and identifies any girdling roots that have developed. For trees caught early, before significant bark decay has progressed, excavation can halt the damage and give the tree a realistic path to stable health.

For trees where the damage is more advanced, the assessment shifts to understanding how much viable bark tissue remains and what the structural risk profile looks like.

Both Hufnagel Tree and Middletown Tree Service do root collar assessments and excavation work for properties in Monmouth County. Either can evaluate specific trees, identify whether burial is a contributing factor in decline, and advise on whether intervention is likely to be effective. The International Society of Arboriculture at isa-arbor.com also has a certified arborist finder if you want to find credentialed professionals by zip code.

The Part That Stays With Me

What I find hardest about this particular problem is that the people who cause it are usually doing something they were told was good practice. Mulching trees IS beneficial, done correctly. Adding topsoil for a nicer lawn IS a reasonable thing to do. Nobody was being careless. They were just not aware of the one specific thing that distinguishes correct mulching from damaging mulching, or that adding soil against a tree base is categorically different from adding it in an open area.

The trees that get this problem the worst are often the most cared-for trees, in the most maintained yards, where people have been consistently investing in their landscape for decades. The attention and the resources went into the right places, just with one piece of information missing.

Getting that piece of information out - knowing what the root flare zone is, why it needs to be exposed, and what the mulch volcano pattern actually does over time - is the kind of thing that saves trees that would otherwise die quietly over fifteen years with nobody understanding why they were declining. In Monmouth County, where mature oaks, maples, and ornamental trees are a huge part of what makes a property worth living on, that feels like information worth spreading.