I used a 9 inch auger. I only have a
BX2200 - and it won't turn much more than that (at least not in heavy soil).
To go back a few steps ... I planted my trees as a windbreak / screen around my property rather than for a business, but did do quite a bit of research before I started. The best resources I found (don't have the URLs handy) were those written by various ag extensions in the mid-west. The recommended process was:
1. Use a ripper to break up the soil the fall before spring planting. It's important to do in Summer or Fall to get the maximum shattering effect in hard soils. This really improves drainage in heavy soils, especially if the land has previously been used for agriculture and may have a hard-pan layer at tiller depth. It lets the roots get down quickly so the trees can better grow and survive dry spells (winter or summer).
2. Use round-up or similar a few weeks before planting to kill off any sod. Turf-building grasses are a major competitor for nutrients with seedlings. Allow enough time for this to break down in the soil before planting. (I think the guideline is 4-6 weeks, but check it!)
3. Till the planting area - usually done in strips. The round-up and tilling can also be done the fall before planting to allow the sod to break down. You can always do a quick clean-up with round-up the next spring if need be - the turf won't have re-established. Tilling really helps the absorption of water into the surface layers of the soil and again breaks up hard soil structures. Pines send down deep taproots fairly quickly (year 3?), but they also have laterals that will benefit from a well tilled soil.
4. Plant the seedlings. Using a post hole digger is optimal for bare-root pines because even the 2 year transplants have amazingly long roots - some of mine were over 2 feet long. You don't want to prune the roots if you can avoid it - it's the depth in the soil that will help them get to the moisture. Be very careful not to J-root the seedling -- you should have enough depth that the tips of the roots don't curl up at the bottom. I'm not sure why, but this kills seedlings. I used my digging bar to score the sides of the holes - they do get a good glaze on them.
5. I applied a fabric mulch (fabric on a roll) after I planted so I wouldn't have to worry about weedkiller around the pines. You can get special weedkillers for brush control around evergreens, but I didn't want to bother doing this every year with kids in the yard. I used some U-bolts and bolted a long piece of pipe across the base of my ROPS and used it like a big toilet roll paper holder - with the fabric being the toilet paper. I then drove along about 20 feet at a time, stopped and went back to slit holes to pull the seedlings through. I used steel pins (get from same place as the fabric) to hold all this down. Don't try it on a windy day! There's a big debate about costs of weedkiller vs mulch. Your decision.
6. Don't over-water. The forester I spoke to said this is a common cause of death. You want to water them well about once a week during the first year only if there is a hot dry spell. If you do any more than this then their root systems won't be stressed enough to send out shoots to find the water.
7. The forester told me sleep-creep-leap is the pattern of growth for years 1, 2 and 3. With all the rain this spring I think mine are already leaping in year 2.
There - probably a lot of information that you already knew - but I got on a roll. My wife has a good laugh about me and my babies outside. I only lost around 5 of them over the winter despite the hot dry summer we had last year. Not a bad percentage. Two of my neighbors put in some root and ball pines at the same time - one lost all of them, the other half of them. They don't laugh at all of my preparation any more.
By the way, you will find that post-holes make awesome mouse traps. I put the holes in and then had to wait a week for planting (trees were late from Musser Forests). There was a dead mouse in about every third hole. I applied the old Indian logic (what they told the pilgrims about putting a fish in the hole before planting stuff) and left them in there - maybe that's why some of the pines are doing better than others!
P.S. Full disclosure - I skipped the round-up steps above (but did do all the rest) because I didn't yet have CFO approval for the sprayer after shelling out $$$ on the Post Hole Digger, Tiller and other supplies. That was a case of penny wise and dollar foolish. In the short time between planting and getting to the fabric mulch I had a real jungle grow back around the seedlings. I had to weed whack it down before I could get the mulch down. Just shows how good that tilled soil was for promoting growth though.
I now have a sprayer and will probably look more into the weedkillers that you can use around evergreens. I already sprayed the seedlings with Sevin this year because the neighbors pines all have bagworm and I had seen a couple on the seedlings.
Good luck.
