Your Three Ash Trees, Jason
Thanks for having me out. All three of your ash trees have the same underlying problem: they're sitting too deep in the ground. That's it. It's the single most common reason trees struggle in the Valley, and it's the reason the one out back looks rough every summer while the others hang on.
The good news is that this is fixable, and most of it is work you can do yourself with a shovel, a hose, and some patience. I've written this up so you have the full instructions for each tree. Where a tree needs more than digging, I've said so. At the end there's an option for the one tree that needs real help.
Why depth is the whole story
What a root flare is and why it matters
The root flare is where the trunk stops going straight down and starts widening out into the main roots. On a healthy tree you can see it. The trunk looks like it has feet. If your tree goes into the ground like a telephone pole, straight sided with no visible widening, the flare is buried.
That matters for a few reasons. Trunk bark is not root bark. It isn't built to sit in wet soil, so when it's buried it stays damp, breaks down, and opens the tree to decay. The tissue that moves water and sugar up and down the tree sits just under that bark, and when it's compromised the whole tree runs at a deficit. That shows up as summer stress first, because that's when the tree is asking the most of itself.
The second problem is girdling roots. When a tree is buried, roots that should be spreading outward instead grow up toward the oxygen near the surface and start circling the trunk. Over years they thicken and squeeze it, like a rope tightening. That's a slow strangulation, and it's usually invisible until you dig.
Here's a short video where I show what this looks like in the ground and how it gets fixed.
If the video doesn't load, watch it here: youtu.be/mLCVVxdvxU8
How to excavate a root flare
Work slowly. The goal is to remove soil without wounding bark or tearing roots. A wound at the base of a trunk is worse than the burial you're fixing.
- Use water, not steel, near the trunk. A hose on a hard jet nozzle will cut through soil and wash it away without damaging bark or roots. This is the safest tool you have. A hand trowel and your fingers work too. Never swing a shovel against the trunk.
- Start at the trunk and work outward. Remove soil in layers rather than digging a hole. You're peeling the surface back, not excavating a pit.
- Stop when the trunk widens. You'll feel the trunk change from straight to flaring. Keep going until the tops of the main structural roots are visible where they leave the trunk.
- Follow the flare out. Clear soil out to where those roots dive down on their own, usually 12 to 24 inches from the trunk on a mature tree.
- Leave it exposed. Do not backfill. The flare and the tops of the main roots stay above soil permanently. This looks strange for about a month and then it looks correct.
- Mulch, but not against the trunk. Two to three inches of mulch over the root zone, pulled back 6 inches from the trunk so nothing touches bark. Never a mulch volcano.
Where the three trees stand
Same problem on all three, three different levels of severity, three different fixes.
Needs real help
The mature ash that has a hard time every summer. Planted too deep, too established to lift. Excavation plus recovery work.
Fix it now
The replacement tree. Looks fine, but it's buried. Young enough that you can still lift it, which is the best outcome available.
In good shape
The mature ash on the west side of the house. Flare is already mostly exposed. Keep going a few inches and you're done.
The one that has a hard time every summer
Planted too deep, and it's been paying for it
This is the tree that tells the story. It struggles every summer because it's been running at a deficit since the day it went in the ground. The trunk tissue that should be moving water and sugar has been sitting buried, and there are almost certainly girdling roots wrapped around the trunk under the soil, squeezing it a little tighter every year.
It's too mature and too established to lift. That option is gone. What you can do is excavate around it, get the flare and the main roots exposed, and deal with the girdling roots. That's a real fix, and trees respond to it.
Excavating
Same process as above, but expect to go deeper and wider, and expect it to take a few sessions rather than one afternoon. Use the hose. Take your time. Every root you accidentally tear is a setback.
The girdling roots
As you dig, you will find roots crossing over or wrapping around the trunk instead of heading away from it. Some of those need to be cut. Some do not. This is where people get it wrong, because cutting the wrong root, or cutting too many at once, can do more harm than leaving them.
- Don't cut anything yet. Expose them first and get the whole picture before you make a single cut.
- Photograph what you find and post it in the Garden Nerd Club. I'll look at each root and tell you which ones to cut, which to leave, and in what order.
- Expect to stage it. On a mature tree with several girdling roots, you often cut some this year and the rest next year so the tree isn't losing too much at once.
- Cut clean when you do cut. A sharp saw or loppers, flush to where it leaves the trunk, no tearing.
The one you just planted
Looks fine now, but it's planted too deep
Right now this tree looks healthy, and that's exactly why it's easy to ignore. Depth problems don't show up for years. By the time a buried tree looks sick, the girdling roots are already thick. You have a window here that you don't have with the older ones.
Step one, find out how deep it actually is
Before you decide anything, dig down at the trunk and find the flare. Measure how much soil is sitting on top of it. That number determines what you do next.
- Under 6 inches: just excavate. Clear the soil back the way I described above, expose the flare and the tops of the main roots, and leave it. The tree is young enough that it will adjust.
- More than 6 inches: lift it. Don't just dig a bowl around the trunk. At that depth, excavating alone leaves the tree sitting in a depression that collects water against the trunk, which is its own problem.
How to lift it
This sounds intimidating but on a tree this size it's very doable in an afternoon with a second set of hands.
- Dig a trench around the root ball, well outside it, so you're not cutting into roots. Work down until you can see the bottom of the ball.
- Undercut it. Work a shovel or digging bar underneath the root ball from a couple of sides until it's free.
- Add soil underneath, not around the trunk. Backfill the bottom of the hole with native soil mixed with quality compost until the tree sits at the right height, then set it back down.
- Set the flare at or just above finished grade. Slightly high is better than slightly low. The soil will settle.
- Backfill the sides with the native soil, worked with compost and organic fertilizer, and water it in well to remove air pockets. Do not pile soil back over the flare.
- Do this in the cool season. October through March. Do not lift a tree in summer.
- Water deeply for the first few months after lifting, since you've disturbed the roots. Then move to the schedule below.
The mature ash beside the house
This one looks good
This is your healthiest tree and the flare is already decently exposed. Someone did the right thing here, or it was planted at the correct depth to begin with. It just isn't quite finished.
What to do
- Go another 3 to 6 inches deeper around the base using the same water-and-hands method above.
- Work all the way around the trunk, not just the side that's easy to reach. Keep exposing outward until the tops of the main roots are showing where they leave the trunk.
- Then stop. No further work needed on this tree. It doesn't need recovery treatment or anything else. Just finish the flare and leave it alone.
Two changes that apply everywhere
Less often, much longer
Short frequent cycles only wet the top few inches of soil, so roots stay up there where it's hot and dry out fast. That makes the tree dependent on you and vulnerable in every heat wave. Long infrequent soaks push water down deep, and roots follow water. Deep roots mean a tree that can ride out a hot week without wilting.
- Water to 3 feet deep. That's the target for a mature tree. Check it with a long screwdriver or a soil probe, which will push easily through wet soil and stop at dry.
- Water at the drip line, not the trunk. The feeder roots are out under the edge of the canopy and beyond, not against the trunk. Move your emitters outward as the tree grows.
- Summer: roughly every 7 to 14 days for an established tree, but a long soak each time. Winter: every 3 to 4 weeks.
- Stretch the interval gradually rather than all at once, so the roots have time to chase the water down.
Pull it back from under the trees
Decomposed granite and rock heat up hard, hold that heat into the night, and radiate it straight down into the top layer of soil where the feeder roots live. It also sheds nothing back into the soil. Every year the organic matter under it breaks down further and nothing replaces it, so the soil biology thins out and the tree has less to work with.
- Pull the rock back from directly under each tree, out to the drip line if you can manage it.
- Replace it with wood mulch, 2 to 3 inches deep, kept 6 inches off the trunk. It cools the soil, holds moisture, and feeds the soil life as it breaks down.
- Top dress with quality compost under the mulch once a year in fall. That's what rebuilds the soil biology these trees run on. Arizona Worm Farm is where I'd get both.
Tree Recovery Program for the struggling ash
Just for the mature ash that has a hard time each summer. The other two don't need it.
What the program does
Excavating the flare stops the damage. It doesn't rebuild what the tree lost over years of running stressed. That's what this program is for. We come out four times a year and inject 25 gallons of our organic liquid blend directly into the root zone under pressure, which puts biology, nutrients, and water down where the feeder roots actually are instead of on the surface. Over a year that rebuilds the soil life around the tree and gives it what it needs to push new root growth and recover canopy.
We can also handle the root flare excavation on this tree as part of it, which saves you the hardest of the three digs. You'd still be doing the other two yourself.
Tree Recovery Program
Each visit includes a 25 gallon deep root injection of our organic liquid blend. If you'd rather handle the digging yourself, the program alone is $475 for the year.
Where this goes next
Start with the newly planted tree, since that's the one where you still have the option to lift it and the window won't stay open. Then the west side ash, which is a short job. Save the struggling one for last, because it's the biggest dig and you'll want the practice from the other two first. All of it in cooler weather, October through March.
You'll be added to the Garden Nerd Club, which is where you can post photos as you go. Send me a picture of the new tree once you've found the flare so I can tell you whether to lift it, and send photos of the girdling roots on the struggling one before you cut anything. That's what the Club is for, and it's the fastest way to keep this on track.
Questions on anything here, just reach out. You can also read more about how we work with trees at thegardennerd.org.