The city used to have two huge (about 40″ diameter) Liquid Amber trees in our front yard which kept clogging up our sewer lines with their roots. Finally a year and a half ago we managed to get the city to let us remove them. The tree guys ground out the stumps and roots down about a foot in about a 6 foot radius with a very big stump grinder. Problem is, the front yard is still a mess, with roots pretty much all over the place under the lawn. We had hoped the roots would eventually rot away, but we had shoots coming up again this month, and on digging up a test section 20 ft from where one trunk was the 8″ diameter root (and its swarm of 2-3″ offshoots) seemed awfully healthy. If they can go 18 months with no food, who knows how long they can go. No way that we will be digging these all out with a shovel, digging bar, and axe. Heck, it took me 10 minutes to chop through the biggest root in just one place with a freshly sharpened axe.
Other than calling in a tree service with another larger stump grinder, is there anything we can do to hasten the disintegration of these roots? The water line and gas line to the house run through that lawn, and given their age and probable delicate condition, it doesn’t seem like a great idea to unleash that sort of mechanical mayhem anywhere near them. These pipes were between the two trees and outside of both grind zones, but there are big roots growing over them.
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persistence will prevail........
The roots can't live without photosynthesis from leaves. So if you keep the sprouts cut diligently the roots will eventually die.Meantime stored food in the roots produces sprouts.
Lawnmower, weedeater whatever is the easiest.
I assume this is L. stryracilua which is a real sprouter., I'd expect to still have sprouts to deal with next year, maybe no more than that if you keep them whacked down. Meantime the roots are not going to be getting bigger.
There are herbicides for this but I wouldn't go that way.
You can paint any sprouts with RoundUp, and you could probably burrow in, drill holes, and inject any of several herbicides. I've also heard rumors of embedding pieces of copper in a tree to kill it.
We decided to drill a bunch of holes in the roots and and pour high nitrogen fertilizer in there. The idea being to give the soil fungi an easy path to the inside of the roots, and tip the scale more towards decay than sprouting. To make those holes I bought a 1" diameter ship's auger:
http://www.irwin.com/tools/drill-bits/speedbor-ship-auger-bits-with-weldtec
and found that in a 1/2" drill it would easily go through the roots. This was tested in the section of roots that we had already exposed.. Then moved over a foot and drilled straight through the dirt (only about half an inch above the root) and that worked too. It is really obvious when the bit hits wood since the feel changes and wood chips come up through the hole. I know that bit is going to get dull eventually, so also bought an auger file to sharpen it back up again. This thing is supposed to be able to chew through nails, but I'm pretty sure that If we hit a rock it will break the bit. For making other holes, when probing around for roots, we also purchased a 3/4" inner diameter, 1" outer diameter, 60" long steel pipe and a hand post driver (the kind that is a large steel tube closed on one end, with two handles, weighing about 15 pounds). It was easy to make 1" diameter holes down through the dirt with it. The only problem with that approach being that the dirt it took out was very tightly packed inside, and it took some poking with a steel rod to clear it..
We know where the pipes are under the lawn and will not be working anywhere near them.
Interesting approach -- Please keep us informed on how it works out.
If you spray any shoots that come up with something like Crossbow (a brush killer) it will be carried back down into the roots. Might take a lot of applications, but it will eventually do the trick.
Progress report.
I have done a bit of root mangling without excavation using the ship's auger. Holes drilled straight down through the surface of the lawn. Here is a picture from today. The big brown spot at the bottom is the section which we dug up previously (and most of the grass chunks died, hence the color). The patch of dirt near the zucchini plants is excavation around a broken sprinkler head - due to lawnmower trauma, not roots. As the holes were drilled they were marked with either bamboo sticks or white planting stakes. It was pretty easy to follow where the root was going, if a drill hole came up all dirt, just go left or right until the drill hits wood. Later I mixed up about one cup of urea in 1 gallon of water, and poured some down each of the holes. Hopefully with the extra nitrogen, and the mixture of dirt and ripped up root in the hole, the soil fungus can start breaking down the roots - from the inside. The holes tend to collapse at the surface, so I expect the lawn surface will look about the same as before it was drilled in a month or so. With luck they will also be raining more dirt down into the holes in the root.
No good way to tell if it is working, short of digging one up, or seeing a huge crop of mushrooms.