Digging holes

I've got 550 two year old trees on bud 118 coming from Cummins Nursery Spring of 2015. This will be my first real orchard. I was going to plant with an 18' in row and 24' between rows spacing. Our soil is extremely rocky and has a lot of clay. I've read through both of Michael Phillips' books on orchards so I was initially thinking I would plow out the rows and cover crop (I did a lime treatment last year and might follow up this year). Cummins told me that that was probably unnecessary for Bud 118 as long as the initial holes were big enough and I had plenty of mulch.
Well, I do have a lot of mulch (which is getting nice and fungal) but I'm worried about the holes. I'm aiming for 3' in diameter and 1.5' deep. The soil is so rocky that hand digging 550 holes is not really practical. My thought was then to buy a 3' diameter tree auger and drill the holes with a skid steer. If the hole is glazed I'd score it with a rake before planting. The other option seems to be to rent a small excavator, but I'm worried that would be too slow.

Any thoughts would be greatly appreciated.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania

Since you mention clay, it is likely having heavy equipment there will further compact the soil..a skidsteer will do this, but the excavator would be a whole lot worse and messy. As far as glazing goes, I have found a manure fork works better than a rake.

Walden Heights Nursery & Orchard
Zone 3 in Vermont

When prepping orchard ground, there are four primary reasons to cover crop:

~ deal upfront with weed seed loading and/or rhizome grasses
~ bulk up on organic matter
~ steer biological activity in a fungal direction
~ prepare "good tilth" for digging holes

The question of scale enters in here as well. Forking out red clover root systems and then hand digging a generous-sized hole to loosen up the soil further out from the roots for a dozen trees is no big deal. Bring in a couple friends and you can do 50 trees in a morning this way. My experience with an auger was with a two-foot diameter bit in rockless ground. Soil amendments (like Azomite clay and rock phosphate) get sprinkled in and around the hole so as to be mixed throughout the soil as it gets packed back around the roots.

Another approach is to sheet mulch, and given your extensive spacing plans for trees on Bud.118, Nathaniel, I'd get right on this. Laying down cardboard would mostly smother sod root systems by next spring ... just take care to fork out grass rhizomes when surface-prepping holes for augering. Putting down mineral soil amendments at this time is a good idea, including calcium in some form. Organic Grower Supply in Maine takes this concept to the extreme in recommending a 32# bag of "fruit tree mix" per hole. This contains worm castings, Tennessee brown phosphate, alfalfa meal, azomite, k-mag, and come form of calcium. Rich compost would be good too, all this directly on the ground (beneath the cardboard). You probably want to mow first, being it's the height of summer, to lay things flat. Atop the cardboard, anchoring it down, goes the woodsy mulch you've been gathering. Thick is good. The biological activity through the fall and even under snow cover will be prepping an even bigger hole in terms of soil friability by the time you auger early next spring. Aim to provide a minimum 4 foot diameter planting circle for each tree with this effort.

Lost Nation Orchard
Zone 4b in New Hampshire

Thanks for the responses. I'll try sheet mulching a 4' diameter area with cardboard for each tree. I'll see what I can get on the ground before the cardboard goes down. I thought maybe I'd use stump grindings on top of the cardboard then follow up with woodsy mulch once the trees are in.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania

I have planted hundreds of apple trees in pretty much pure clay with close to 100% success. I used a 12" auger, and trimmed the roots back to fit the hole. Tree roots will re-grow at the tips of the roots that are left, be that at the end of a 2 foot long floppy root (which gives no support) or 6" from the trunk. I never bothered scoring the sides of the hole. The type of clay here in the Champlain expands and contracts with drying/wetting and freezing/thawing. Any "glazing" cracked and disapppeared pretty quickly.

I would consider a 3 foot auger way overkill. All those floppy roots just get in the way. I know this all runs counter to standard thinking, but it works. And you don't get much clayier than here.

Jim Gallott
New Haven, VT USDA Zone 5a

Having used both an auger and an excavator in clay and rocky ground, I advise in favor of the excavator.
I have used mine a lot and for a tree hole it is faster and does a better job than an auger, without concern of hole glazing. Our experiences with the auger in our stone and clay ground are disappointing. Time spent replacing shear pins and the holes that can't be bored without a bunch of sweat expended in breaking rocks so the auger will go deep enough can really add up time and frustration wise. Depending on the size of excavator, one or two buckets and you are on to the next hole. The number of holes you are digging could be done in a day or 2. That's just my 2-cents because of years of frustration using augers in this ground.

Not that it will convince most of you out there, but consider this:

5 eighteen year old kids could do it in less than 4 days without sweating. Consider: 550 trees at 15 minutes a hole (that is some lazy digging), puts things at 27.5 hours a chap or gal. At a fair 12 bucks an hour this translates into 3 measly bucks a tree. This means dug, planted, and staked likely.
We did one of our plantings here of 245 trees in less than 2 days with 5 people. It employed some young people around here that really needed the work, and the company wasn't bad either. Just a thought.

Walden Heights Nursery & Orchard
Zone 3 in Vermont

I would like to echo Todd's recommendation to consider some manual labor.

It wont be too long before you may need some help in harvesting those 550+ trees perhaps and having some trusted local labor supply will be very valuable indeed. We apple farmers always need to be thinking several seasons ahead

Helping some local youth get some hands on work, for good pay, and the experience that comes with it, may well help to inspire some future farmers to take up the career, as well.

Our local Ag program, at the high school, is regularly looking for hands on Ag related activities for the students as the kids need it for their FFA and Ag class required work experience credits. If you are unsure where to look for the youth help, get in touch with the local Ag instructor at one of your local high schools. They will be happy you called.

Good luck!

Gopher Hill Apples
Zone 8 in California

Thanks for the tip about calling the Ag program at the high school. I'd prefer to go with manual labor on the holes, but my back still approximates the typical 18 year old (until I wake up the next day) and so I know first hand that digging a 3' wide hole is our earth is not a 15 minute affair, even with the ground made more friable with sheet mulching this past fall.
I ended up meeting up with a local contractor who is trustworthy and can have one of his guys work the excavator for $500 per day. He reckons 2-3 days and the holes are done. So, I'm budgeting for 3 and hoping for two and concentrating on getting all my volunteers planting properly.

Two days into planting 550 trees--our first orchard of any substantial size. Just a tad more difficult than I anticipated...a tad.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania

If you run into a lot of rock, an exavator is about your only option. You couldn't buy enough shear pins for the auger. A smallish excavator can easily work a 2 ft bucket with 1-2 scoops per hole and will run less than $100/hr with an operator. I estimate a good operator can dig 40- 50 holes per hour and now I'm using my time elsewhere on the farm, not digging or supervising labor.