M111 is often chosen for its resistance to Wooly Aphid, which it will maintain even if the scion roots. It is an 80% size tree, and adds a little precociousness. I think your plan is sound.

Applenut

Depends some on the scion. 111 is only considered slightly less dwarfing than M7 and is certainly not nearly as vigorous as trees I manage on seedling in my conditions here. Generally I'd estimate 111 to be about 70% of standard vigor- 7 about 60%

If trees are vigorous varieties(think Fuji, Northern Spy) trees could become significantly more vigorous with scion rooting, if they are precocious spurry types like Braeburn or Goldrush there'd be no affect, I guess.

People tend to underestimate scion in determining relative vigor of trees. My Goldrush on 111 are less vigorous than N Spy on 26.

It is a sound plan, but you could just plant them slightly below soil line, mulch and sever scion roots at least until trees are fully bearing.

Are you sure FB thru burr knots is a problem? Could be but this is the first I've heard that. I think you'd be fine if you put the union just above soil line and make sure any burr knots root by piling soil around the burr. But if you don't mind a bigger tree and possibly a few more yrs till bearing, then bury the union.

The Fruitnut

Thanks for the useful responses.

This is not where I originally read it (that mentioned MM-111 specifically) but gives the idea. I definitely have a lot of dogwoods around, and thus probably borers. And the MM-111 rootstocks are covered with burr knots above the present soil line.

I like the idea of burying the graft shallowly, cutting the scion roots for a few years, and then when fruiting letting it go. I wonder also about a thick paint as protection instead.

http://books.google.com/books?id=_-MePLY9imoC&pg=PA260&lpg=PA260&dq=%22burr+knots%22+blight&source=bl&ots=adp4U9Ajyi&sig=QxanZqF28YfFa-nDp22cGTgUWIA&hl=en&ei=f1e6SvuqKsGw8Qa_4vSMCg&sa=X&oi=book_result&ct=result&resnum=2#v=onepage&q=%22burr%20knots%22%20blight&f=false

Where you do have real danger from fireblight is root suckers; if blight drips on them from above and it gets down into the rootstock, it will eventually kill the tree.

Regardless, planting the rootstock high and developing burr knots is not healthy for the tree in the long run.

My understanding is that fireblight is not an issue as long as you keep the root stock from suckering (providing green leaves from the root stock). I have fireblight with my pears, but I have never had an issue with fireblight on the apples planted nearby on M111.

I'm confused... I thought if you buried the graft union, you could expect a standard size tree eventually. This would present many problems in a 10-15 gallon pot, I would think. But I am no expert. Even if you prune heavily how can a 15 gallon pot support a standard size apple tree? Just wondering, I am not stating that it isn't possible..

Also, I have burr knots on all of my mm111 trees and I was told that the burr knots invite borers, and to deter them, paint Thiodan on the burr knots around Labor Day.

I recently had my first tree fatality, it was a Horse apple on mm111 and I lost it to collar rot. Wasn't expecting that one..

The 10-15 gallon pots are just to keep the plants in a place I could better protect them for a year, in order to grow a better root system and bigger top before field planting.

I also budded some onto dwarfing stock of several types to experiment with in 40 gallon pots in the backyard.

Actually, if you keep a vigorous rooted tree in a pot it will fruit much sooner and behave like a dwarf. It works like root-pruning, only better.

Finding good info about burr knots is driving me crazy. I've decided to plant the graft union. Not bothered about vigor becs there are other means to control that. My worry is that planting too deep is also considered a serious problem that can cause many tree deaths after a decade or so. Sigh. Any comment on planting too deep?

I have heard the best thing to do is bury almost the entire mm111 rootstock up to just below the graft union. All burr knots now and in the future will be then be underground. As far am I'm aware the burr knotts will only ever be on the rootstock - unless the specific variety you have grafted is susceptible to them.

I have grafted many MM111's this spring and I intend to use this method when planting into the field in the next year or so.