Augering holes around dripline

pam29011August 22, 2011

We had a lot of work done in the yard last fall and this spring. We thinned a dense forest down to keep the large, healthy, straight trees.

In the process of this work there were trucks in the yard. And we had some of the site graded to correct some low spots that were causing problems. The guys who did the work said all the right things to indicate they understand trees (they didn't use the bulldozer anywhere near the trees & spread a thin layer of loam by hand over the root zones).

But still - there were trucks in the yard and I'm pretty sure some soil compaction has happened around the trees we want to keep alive. So I bought an auger (1.5" diameter, 18" long) to aerate the soil around the drip line.

Question is - what do I put in the holes after I drill them? I've read that I should use peat moss, peat + manure, and small gravel. Will peat last, or will I have lots of holes in the yard in a few months?

Any ideas on what the right answer is? I planned to do this this week or next (while I have time off). Is there a good or bad time to do this?



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hortster(6a, southcentral KS)

We used to do a treatment on pin oaks to combat chlorosis. An antiquated, now virtually unused method. We would drill holes 18" apart, in rows 2' apart, in an area 6' in from the drip line, 6' beyond the drip line. There was a mixture of sand, sulfur, and chelated iron that we would apply. I'll be darned if it didn't eliminate the chlorosis for a few years. The point here is, maybe filling the holes with sand at the same intervals so that the soil could breathe might help. You also might google "trench composting." Still not sure if I buy that one, either.

    Bookmark   August 22, 2011 at 8:35PM
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treebarb Z5 Denver

Pam, I'm still a rookie with more questions than answers but I know the experts will be posting soon.

I'm wondering it would be beneficial to add mycorrhiza to the holes.

Where are you located and what's your soil type and ph?
What kind of trees, how old and how large?


    Bookmark   August 22, 2011 at 9:07PM
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dan_staley(5b/SS 2b AHS 6-7)

Won't frost heave crack the compaction? I'd want to ensure water gets in there to expand, so gravel is out. Compost is fine. Should already be myco in the soil. As we don't know the soil type, anything else is a WAG.


    Bookmark   August 22, 2011 at 11:17PM
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ken_adrian Adrian MI cold Z5

1.5" diameter, 18" long ????

lets get this right... are we talking something like a drill fitted bulb planter???? ... 1.5 inches by 18 inches????

something like the link????

just let the augured up soil fall right back in the hole ...

you might also think about simply aerating the lawn with one of those walk behind gizmos ...

you dont mention your own soil type ... but i would not make pockets of anything high peat .... once peat dries by july/august.. you are just going to have little pockets of water repellant peat .. and that will not be good ... if anything a good local topsoil would be about all i would suggest ...

if you fertilize the lawn.. the trees will get what they need ... i dont see any real benefit to injecting it ...

if there is any drought .. i would simply water the lawn deeply .... again.. the trees will 'get' what they need ...

i think you are simply down to prayer .... if auguring makes you happy.. go for it .... i doubt you can harm anything ...

good luck


Here is a link that might be useful: link

    Bookmark   August 23, 2011 at 8:49AM
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Thanks for all the feedback :)

I'm in New England, so our soil is rocky with large amounts of sand and decayed leaves & pine needles.

The trees I'm trying to save are mostly oak with one maple. The oaks range from 2.5 - 4.5 feet in diameter, measured at chest height. The maple is smaller at just under 2' diameter. The trunk flares on the oaks are HUGE (and almost shaggy with moss on the north side). It feels almost prehistoric walking through there - like Jurassic Park.

Where they added soil to grade the yard, they added loam that is more clay-ey than the soil that was here. It isn't bad (I've lived in the South with red clay before) but it seemed heavier than what I'm used to here. Thankfully, they didn't add much over the tree roots (just raked up 1-2" to blend with the places they added soil to) but still ...

The size of the trees is what makes it worth just about any cost to save them. If they die I'll have the guilt of killing 100+ yr old oaks that WERE perfectly healthy and the expense of getting the trees out of here. If you figure $1000/tree to cut & remove ... well, spending a couple hundred bucks on a heavy duty auger, a big drill, and whatever treatments go in the hole seemed like a cheap option.

I linked to the auger below. Based on all of your advice I think I'm going to go with coarse sand + some bagged, composted cow manure in the holes. Should be a fun way to spend a couple days ;)

Here is a link that might be useful: Heavy Duty Garden Auger

    Bookmark   August 23, 2011 at 9:36AM
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ken_adrian Adrian MI cold Z5

i dont understand.. how you take all the above. and come to the conclusion that manure will be beneficial????

is there a lawn .. is it fertilized.. and if so.. why do you need to add more fert???

all of us ... would tell you.. short of horrible clay.. that a tree should be planted in native soil.. with no amendments.. and no fertilizer .... and nothing else .. unless a soil test indicates something is lacking from the soil ...

so why are you adding to the soil???

i am concerned.. that you are on the verge of trying to love your trees to an early death ...

they have been there.. for a hundred years.. w/o you .... why are you now thinking they cant live without you???

i dont think the auger is going to do any harm.. and it might make you assuage some of your guilt ... [boy i didnt think i would ever work that word into a sentence in my life.. lol] .... but i am just trying to get you to be very careful about loving them up too much to their detriment ...

you would probably be further ahead with a 16 dollar 50 pound sack of 12-12-12 broadcast over the lawn.. rather than micro pockets of manure or compost ... the odds of hitting a feeder root is low to nil ...

some say.. [apparently i do repeatedly] that a tree is twice as big underground as above ... in a differing form ... regardless.. can you tell us where the feeder roots are???? i cant ...

your holes are akin to pounding in tree spikes.. and i cant think of one person here.. that thinks those are worth the cost nor effort ... so it should follow that a bunch of little holes of compost/manure is going to do much ... except make you feel good .. which is a good thing for you ...

i wish you all the luck in the world with your glorious trees .. just dont go overboard with them ..


    Bookmark   August 23, 2011 at 3:39PM
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rhizo_1 (North AL) zone 7

Here's what I think might happen if you put something too nutrient rich back in the'll end up with dark green polka dots in your lawn (if you extend your augering into the lawn). I've seen that happen a few hundred times, back in the good ol' days when big cores were removed and all that good stuff poured in the holes.

Honestly, the best thing you can do is to rake the soil that came out...back in the holes! You know yourself that peat moss will eventually disappear and compost will do so even faster.

The most common method of soil aeration these days, including around trees, is with a core aerater that will pull zillions of small diameter, 6 or 8 inch plugs out of the soil. Doesn't really need to be any deeper...that's about where the majority of the fibrous (feeder) roots are. Those plugs are then raked (or run over with a drag mat) back into the holes. What a benefit. Maybe something to think about for the future. Core aerators can be rented from most well-equipped rental facilities.

    Bookmark   August 23, 2011 at 4:03PM
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dan_staley(5b/SS 2b AHS 6-7)

It is my assumption that the OP will rake the soil back in the holes, and my recommendation was to add compost. I see others aren't getting that vibe. And what ken said.


    Bookmark   August 23, 2011 at 5:50PM
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SO ... Let me ask my question another way ...

If you believed that there was some soil compaction that happened around your trees, how would you try to fix the situation?

Imagine that while you were on vacation, random thugs drove around your yard in heavy trucks (IOW - no fair to answer with, "Well, I'd never allow such a thing to happen"). After filing police reports, what would your next step be if you wanted to minimize the damage to your trees?
--------------- ------------------ ------------------
To answer the questions raised earlier in the thread ...

I should have been more clear. I was thinking I'd take the soil that comes out of the holes and mix with some coarse sand & composted manure. I left out the step of "pick up soil that comes out of holes" because ... well it seemed obvious. Otherwise I'd have little lumps everywhere that would look like carefully spaced poop piles. Our dog isn't that precise.

"they have been there.. for a hundred years.. w/o you .... why are you now thinking they cant live without you???"

Because I messed with the soil they live in. I hired people with trucks & other equipment to thin out the forest, and that is VERY likely to have compacted the soil. The trees now have less competition for water & nutrients, but if the soil compaction limits how much oxygen they can get then they could still die, yes? I figured (perhaps stupidly) that sand + soil would have better air flow than the same dirt that came out of the hole, and a little composted manure is like my daily multivitamin. I take the vitamin, I don't know if it does anything good but I figure it won't hurt. Same deal for composted manure. It won't burn the roots, it might help, and it can't hurt.

I didn't think a core aerator would go deep enough to make a difference, that is encouraging because it would be a quicker way to cover the amount of ground I'm looking at. As suggested, I don't know where all the feeder roots are but my understanding was that if you looked at the drip line as a circle, and drew a donut shape on the ground that was about 3' inside the drip line and 3' outside the drip line (6' wide donut), you're in the right ballpark of most of them.

And yes, there is the start of a lawn in this area. And it was fertilized before we put down seed, with a decent application of 12-12-12 fertilizer.

    Bookmark   August 23, 2011 at 10:32PM
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gardener365(5b Illinois USA)

A tree-codger once stated to me...

Trees stressed from old age (or I think personally Pam's case qualifies) will not be harmed but it can be rather beneficial to fertilize them from time to time. The method has already been repeated here from horster - You'll do the augering and it's easiest to have someone follow with a bag of 12-12-12 or similar (10-12-10, 10-10-10, etc-) and they add a heaping teaspoon into each hole. The application is finished as soon as the fertilizer is dropped into the holes. There's nothing more.. you don't return and try to fill them up or anything else, you just leave things be.

I used to do the same thing with mycorrhiza working for an organic tree service a decade ago, but we scooped about 1/2 a cup upwards of a cup into each hole; also our auger was 36" - not any wider I don't believe though.

Good luck whatever you do or who you choose to believe...


    Bookmark   August 24, 2011 at 8:06PM
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brandon7 TN_zone(7)

There isn't enough information to recommend a "fix". An evaluation of what has occured (how much compaction, where the soil was compacted, etc), conditions at the site (soil type, species of trees involved, etc), and other factors needs to be made. Recommendations to apply fertilizer seem way off base to me. Without even a soil nutrient analysis, this is a shot-in-the-dark aimed in a random direction, at best, IMO.

    Bookmark   August 27, 2011 at 8:35PM
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gardener365(5b Illinois USA)

Excuse me, not a teaspoon but a heaping tablespoon.

Again, good luck whatever you decide to do.


    Bookmark   August 28, 2011 at 6:37AM
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