Root Collar Excavation

Go look at where your tree meets the ground.

A healthy trunk flares at the base like the foot of a wine glass — the buttress roots showing, widening out into the lawn. A trunk that goes into the ground like a telephone pole is a tree that was planted too deep, mulched too high, or both. The flare is down there somewhere, and bark that was built for air is sitting in the wet.

Here's the part that surprises people: you may not have done any of it. The flare is often buried before the tree ever reaches your yard. Nursery cultivation piles soil over the structural roots in the field, and again when the ball is dug and wrapped, so a tree can arrive with three or four inches of dirt already sitting on its collar. Set that ball flush with your grade — exactly what a careful crew would do — and the flare goes in four inches deep. Nobody made a mistake you could point to. The tree is buried anyway.

Why it kills slowly: bark at the collar isn't root tissue. Keep it buried and damp and it rots, and decay goes in at the one place the whole tree depends on. Meanwhile the roots that should be radiating outward hit the buried, compacted zone and turn — and a circling root gets thicker every year until it's strangling the trunk it belongs to. Girdling. The tree thins from the top, drops leaves in August, and gets blamed on drought, or a bug, or just getting old. It was the planting depth the whole time.

More UA tree decline traces back to mowers, mulch, and planting depth than to anything an insect ever did.

“The roots are lifting my driveway.” Maybe.

This is the call that ends in a removal quote more often than it should. A slab is heaving, a walk has a lip you catch your toe on, there's a crack in the foundation wall — and there's a big tree ten feet away, so the tree did it. Sometimes the tree did do it. Often enough the slab was poured on fill that settled, or the crack has been there since the house was framed, and the root everyone is pointing at is a passenger.

Air settles it without committing to anything. I take the soil off along the slab and we both look at what's actually under there: whether a structural root is bearing on the concrete, how big it is, which way it runs, and — the part that decides everything — how much of the tree is standing on it. Sometimes one root can come out cleanly, cut in the right place, and the tree never misses it. Sometimes that root is one of three on that side, and cutting it buys you a flat driveway and a tree that goes over in the next wind. Sometimes the tree didn't do it at all, and you keep both.

Either way you find out before anyone starts a saw, and it goes in the tree's chart with photos. If you're holding a removal quote from someone else, opening the ground is the cheaper thing to do first — and it's the same read I'd give you on a second opinion.

The tree that comes down tells on the rest.

When a tree on a property has to come out, I do it or I'm on site for it — and either way I read the tree. I split the stem and follow the decay from the roots up. I pull the root plate and look at what the planting left behind: a serviceberry I took out still had its burlap and wire cage on. Nobody had ever taken them off. On mature removals and big deadwood jobs I autopsy what comes down — borers, carpenter ants, scale, the signatures of disease — because the cause of one tree's failure is the best read you will ever get on the others standing around it.

Most of what I find started at the collar. A tree that goes over in wind mostly doesn't fail at the top: it tips, root plate and all, and the plate shows the girdling root, the decay where the trunk sat buried, the roots that never spread because the tree was set too deep to begin with. If one tree on your street went over this month, now is the time to look at the base of yours.

Asked and answered.