I get a lot of questions about “cutting away roots” from mature trees. So, I thought it was time to re-issue the rules that I have live by and given out for years. Rules that most of the tree experts I know have authorized themselves. Again, these are not the only rules that exist, just the ones I’m familiar with.
Having said that, I’m sure that this is not going to answer every question about ‘root cutting’ that exists. But these are the protocols that have served us well here on the GardenLine radio program and social media outlets for years. And please keep in mind that there is not a one-size-fits-all answer which everyone can live by. But it does start with this – Do not take out more than one BIG root per year on mature trees.
Understandably, there are so many more questions that need to be asked and answered before anyone jumps out there with an axe or machete or chainsaw. (By the way, a chain saw should never be used in and around dirt, unless you want to ruin it.) The first ultimate rule by which to live by in these instances, when someone thinks they can “cut out one big root per year” is that it’s all for naught, or a superior effort in futility if you don’t get that tree on a deep root watering/feeding program. Yes, that same deep root feeding protocol that I have rang the bell on every day for the last two decades. If you’re unfamiliar with those concepts, and you have this unquenchable desire to start severing roots, please read the tip sheet first: Deep Root Feeding
Besides the big roots that are obviously part of what we know as the tree flare, or the evident anchor roots that have developed and are noticeably slanted up towards the tree’s trunk at its base, the other apparent big roots above ground are further anchor roots or they are pushing themselves closer to the soil surface in dire need of finding moisture – hence the need for deep root watering.
And if they truly are “anchoring” the tree, now you also see the ultimate need to heed the rule: You can only prune out one big root per year! And theoretically you shouldn’t do this kind of work yourself, unless you have direct experience, such as actual tree experts. That’s because 1) It’s actually much harder than it looks, 2) If you get overzealous you could actually do more harm than good and de-stabilize the tree, and 3) Again, if you do this without a deep root watering/feeding regimen from now one, it’s worthless.
Finally, there are some folks who think they have to “root prune” because they fear roots heading toward a sidewalk, a driveway or just the house’s foundation in general. If this is your worry, then you actually need to have a true Root Barricade done, because in order to successfully stop the action of concrete movement (on sidewalks and driveways) or to protect the home from roots supping all the moisture from under a foundation, it should be pretty clear that you would need to cut more than one big root. Again, this is why a professional should be called in for root barricading. I don’t normally recommend root barricading to protect sidewalks, but for driveways and especially for foundations, you can always call the program and we can hone in on who might be best in your region for root barricading.
I suppose this also begs the question: Why can’t I just cover all those roots up with dirt, compost or mulch? Again, it’s an effort in futility, if you don’t start a deep root feeding/watering regimen. Besides erosion, the number one reason these roots are coming to the surface is because the tree is in dire need of moisture down in the zone of 6-18 inches, where the root system truly does its best work. So, when you know erosion isn’t an issue, then that’s the tree sending you a message that it’s not getting moisture in that aforementioned zone.
Plus, (even if all things being equal, the tree is otherwise healthy and you have lots of roots exposed), you’re still warned to never bring in more than about an inch of that soil or compost to cover up everything. If you do 2 inches or more you run the risk of ‘suffocating’ that feeder root zone. Once again, this would be another ‘effort in futility’ and a future death sentence to the tree.
So, let’s end this serious discussion with a bit a humor that occurred, last time we got into this Root Pruning discussion. In my world, I have to deal with a lot of people “hearing only what they want to hear.” Case in point: Last time we dove deep into this topic, the next day on the radio show, someone called in to the program to take issue with me on…“why do I recommend only taking 1 tree out per year?” I don’t!!! I have, for years, talked about only taking 1 big root per year away from mature trees.