What the root collar is
The root collar (also called the root flare or trunk flare) is the transition zone where the trunk widens into the buttress roots — the structural roots that hold the tree upright. On a healthy tree, the root collar should be visible at or just above grade. The bark in this zone is adapted for above-ground conditions: it's exposed to air, dries between rains, and resists fungal colonization.
Why buried root collars kill trees
When soil or mulch covers the root collar, the bark above grade is now constantly in contact with moisture, soil microorganisms, and decay fungi. Over months and years, the trunk bark in this zone rots. The tree responds by growing adventitious roots (roots emerging from the trunk above the original root system) that often grow in circles around the trunk — eventually becoming girdling roots. Meanwhile, the natural taper and structural integrity of the trunk-root junction degrades. The tree may look healthy in the canopy for years while the root collar quietly fails.
The three causes we see in DFW
1. Planted too deep. The single most common cause. Nursery rootballs are often delivered with soil already covering the root flare, and the planter sets the rootball at grade level — burying the flare under 4-6 inches of soil. Without intervention, this tree will decline.
2. Mulch volcanoes. The cone-shaped pile of mulch piled against the trunk that you see on virtually every commercial landscape and HOA front entrance in DFW. Looks tidy. Kills trees.
3. Grade changes. A new driveway, patio, or landscape installation that raised the soil grade around an existing mature tree. The tree was healthy at the old grade; now it's slowly suffocating.
The RCE procedure
We use an air spade to gently expose the root collar — typically a 24-36 inch diameter excavation centered on the trunk. We document the depth of burial, identify any girdling roots, photograph everything, and present options: leave excavated (preferred — restores the natural condition), prune any girdling roots, install a permanent grade ring if regrade is desired. The whole procedure takes 60-90 minutes for most trees.
When you should suspect a buried root collar
If your DFW tree has unexplained decline, sparse canopy, smaller-than-normal leaves, or appears to have a "smooth" or "telephone pole" trunk that emerges from the soil without any flare — schedule an arborist visit. RCE can reverse years of slow damage on a tree that's not yet too far gone. Cost in DFW: $300-$700 per tree, depending on depth and complexity.