The hole

KevinS

KevinS

Branched out member
Location
ontario
The region a buddy of mine works for has a planting contract out right now and the holes must be dug with a toothed excavator/ back hoe not an auger of any type to avoid any chance of glazing.

Where I grew up it is solid clay and if you get through that there is more clay, at the truck pulls they leave black skid marks on the dirt. I have worked around backhoe, etc and while digging the sides of the hole are smooth and shiny. So I don't believe that they don't glaze.

The trees that are being planted are 50mm caliber trees (mixed species). They are mainly boulevard trees and all there boulevards have been stripped of original soil and better mixed/ engineered soils we brought in to replace them specifically so trees/ plants would do better(not sure the exact mix).

In the past we have used a shallow 3-4' auger on a skid steer on dingo. Most of these trees are doing just fine.

So my question is does anyone have any facts, knowledge, experience where a auger is a bad choice of tool for hole digging or the excavator being the best choice? Most people would say a tree spade is the right tool but I believe it glazes to.

Thanks, sorry if it sounds like a rant, but love to hear back anything to do with it.
 
No comprende--if these are going into engineered soil, what's it matter? I think excavator better cuz it can fracture deep and cultivate wide.
 
guymayor said:
No comprende--if these are going into engineered soil, what's it matter? I think excavator better cuz it can fracture deep and cultivate wide.
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That's what I wondered as well if it's a 30" rootball and you auger a 48" hole into engineered soil it should be fine
 
Just skimmed over the original post and did not pick up on the engineered soils. My comment was intended for natural clay soils and auger use.
 
To me - there would be financial rewards with using the auger. Which could be used to offset the cost to AVM the trees shortly after install.

Total cost may be parody with excavator method, yet be more effective for long term enhancement of vigour.
 
Mangoes said:
To me - there would be financial rewards with using the auger. Which could be used to offset the cost to AVM the trees shortly after install.
Total cost may be parody with excavator method, yet be more effective for long term enhancement of vigour.
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Definitely--even going around with a pick to break up that interface can be fast and effective.
 
I've heard the argument against using augers for digging tree planting holes. The reason stated usually is because the glazing it causes on the walls of the holes makes it more difficult for roots to penetrate. However, I think you can use an auger and still eliminate the glazing during the backfill process. Guy mentioned using a pick. Sometimes, also, the auger only excavates a hole slightly larger than the root ball. This too can be undesireable for growing roots. I've used an auger to plant hundreds of trees and both these problems can be mitigated easily. During backfill, I'll use a shovel or spade to break apart the sidewalls of the augered holes. This broken up soil is thereby the first soil used around the rootball for backfill. It's broken up and loosened during the backfilling/watering/mudding-in process. Then the excavated soil (from the augering process) is pushed into the hole. You end up with a hole that has been excavated wide with no glazed sides. I agree that glazed hole sidewalls can certainly result from the use of an excavator. So, simply requiring that tool instead of an auger doesn't prevent the undesireable effect. I'm not a big fan of preventing the use of certain tools. The results of their improper use are what we should strive to avoid. Of course, this makes writing specs a bit more challenging. It's also kinda difficult to inspect a newly planted tree to see if the sidewalls of the now filled-in hole are glazed. It's much easier to just check in on the crew a few times and make sure they're not using an auger.

By the way, doesn't anyone dig holes by hand anymore? I have seen specs that require that. If I were trying to avoid glazed sidewalls, and make writing specs easy, I would opt for requiring hand-dug holes. (I am aware that shovels can also cause light glazing in heavy clay soils)
 
Sounds too me that the entity making the contract specs had a bad experience in the past with someone using an auger and doing a poor job. Not so much that it glazes the soil more than the excavator. My only concern with the auger is that it may not be wide enough for the size of tree going in and/or it is way too easy to dig a planting hole that is too deep if your not careful. It can happen with an excavator too, so who really knows why they have the specs that way. If they're really concerned about the glazing, then have them hand dug.
 
chewbacca said:
During backfill, I'll use a shovel or spade to break apart the sidewalls of the augered holes. This broken up soil is thereby the first soil used around the rootball for backfill. It's broken up and loosened during the backfilling/watering/mudding-in process. Then the excavated soil (from the augering process) is pushed into the hole. You end up with a hole that has been excavated wide with no glazed sides.
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There ya go; that's another way. Re specs, if 'flare to grade or higher' is in there, the rest is easier. 'Hole 2x diameter or more' is accomplished with shovel, pickaxe, or compressed air *and/or water*, as with the big Air Knife.

btw the A300 Planting Standard changed last go-round; used to say 'hole no deeper than rootball', changed to 'hole no deeper than rootball, directly beneath the rootball', to allow deeper soil fracturing beyond that point, to facilitate deeper root growth, drainage, and other good stuff.
One small step toward dissolving the self-fulfilling myth that nature tends to make root systems shaped like pancakes.
She may have made fools like us, but her trees are smarter than we give them credit for.
 
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