Those sound like a very quick way to drown or destroy the tree, actually, even with the drain holes. The roots will rapidly girdle the container and that's...well, not good. Either the container will give way or the tree will.

I'd try to find a dwarf cultivar instead.

The rootstock is used to control the height of a tree, actually the size. On top of that is grafted a scion; which is a twig cut from the variety of the fruit you wish to reproduce. Not so common is to put a scion from a smaller sized rootstock to control the size. I did this with apples. I used what is called an M-111 rootstock which is a large semi-dwarf sized stock but it grows very well in clay. To that I put a smaller semidwarf scion and then on top of that; apples of my choice. I did a McIntosh, a Cox's Orange Pippin and another tree that now has 4 different apple varieties.

But the common method is to buy a dwarf, a semidwarf, or a semi-full tree and plant it. But particularly with apples there are many sizes within those 3 groupings. Most suppliers of fruit trees don't reveal the rootstock used. One that does is Fedco Trees in Maine. They sell seedlings, scions and the rootstocks. The scion sales end on Feb 19 and the rootstocks are all sold out.

Graft a scion onto a rootstock and keep it trimmed back every year. I'm not really understanding the planting methods you suggested.

Thanks for the advice but I'm aware of rootstock and dwarf sizes I'm trying to find out if there's a way to take a standard tree and dwarf it by planting it in a some type of a container looking at someone who's tried it drainage for me would be no problem. I realize planting a standard tree in a large container will naturally dwarf it but I was concerned with the roots freezing in winter so if you plant it that would take care of the winter issues with it.

Containerizing a tree is a semi-natural dwarfing method. If you restrict the root run, you will restrict sizing as well. But sinking a container in the ground will adversely affect drainage no matter how well your inground soil may drain. That is just the nature of container gardening. And there is also the ongoing need for removal, root pruning and refreshing of the potting media on a relatively routine basis.

btw, if your climate is suited for growing the olive and avocado in the ground, then growing them in a container should not be too much of a worry. Containers can be protected against periodic cold snaps.

I'd also like to understand your wish for no pruning. Even dwarf fruit trees will need pruning from time to time to make sure they are productive and with good fruiting ability.

I'm not in a good zone for avocados 8B which no one around here recommends them I don't mind pruning but if there's a method out there which can naturally dwarf a standard planted tree I would be crazy not to investigate and see the possibilities that's why I'm asking the question I was worried about what would happen to the roots if I would have to uproot it every 5 years or not. Drainage for me would not be a problem since I have a large berm I would have a drain pipe system underneath the tree with gravel it was the roots that I was kind of not familiar with. If the plant would die in 5 to 10 years if I did not uproot it then I would not want to do the container but if it would just stop growing and produce fruit to a particular size that's what I was interested in.

I also seen on YouTube people planting three plants within 2 ft of each other in a triangle they say That's supposed to take a standard tree down to a semi drawer maybe I need to look into that.

Let me state again, sinking a container down into the soil will adversely affect drainage despite how good your inground drainage may be. That is just the way it is with container planting. And 3-5 years is the suggested time frame for repotting and root pruning of any woody plant grown in a container, dwarf or not. Not repotting and root pruning will lead to the decline of the plant, including the ability to flower and bear fruit.

I would also take a lot of what is found on YouTube gardening videos with a very large dose of salt. Many of them are just nonsense and some are just outright inaccurate. Planting 3 avocados within 2 feet of each other is not going to work out successfully at all!

Some plants can take being planted close together, like Thuja and cypress (mine work well). In some cases, one tree will overshadow another and at least seriously damage, if not kill it (or them if you plant three). Sometimes they get on fairly well (as Thuja is famous for). Sometimes they fight chemical battles with each other.

I'm not sure how avocado and olive will do, but I suspect not well. This is not an experiment I'd try without some considerable research.

I would agree I don't think avocados close together would be a good idea either just trying to think outside the box to make my life easier comes down to it I'll just plant them in the ground and do pruning it 12 ft and hope they fruit instead of continuing to put on new limbs trying to grow taller and bigger

Could I ask why not a dwarf olive trees (down to six feet tall, although some of those are non-bearing and you probably wouldn't want one of those) and a Wurtz avocado at 10' tall? The Little Cado is out there too. Both look to be bearing avocados and small enough to toss a tarp over (with a ladder and a huge tarp) in a cold snap if necessary.

I don't have direct experience with these trees, but I'm sure somebody does--or there are online reviews.

"...from 30’ tall to 15’...'

As I see it, the only way to reduce a 30-foot-tall plant to 15 feet is to prune it halfway back.

I suppose you could bury it 15 feet down, but it would die.

The olives that I want I don't believe they have dwarf, I could be wrong though I'm not sure what rootstock these are on and I want the Mexican type avocados for my zone 8B, I'm only buying trees recommended at 20° the wurtz is a little higher than I would prefer if I remember correctly

https://homeguides.sfgate.com/grow-wurtz-avocado-44455.html

A Wurtz should only go to fifteen feet or so, which seems about right. Although things will tend to exceed their genetic parameters if they're happy (ask me how I know...) :-)

Bark inversion grafting can dwarf a tree. The width of the inversion determines the dwarfing effect. The first attempt may be overkill or have insufficient dwarfing effect.

The downside is that using this type of restriction will force sucker development below the inversion graft. Also, a failed graft could cause the death of any scion remaining above the procedure location.

All right I'll play along, how do you know.

When I get back to the house I'll see what temperatures it can take if it goes down around 20 degrees look into it

I seen on YouTube a nursery made a complete cut around the cambium layer of a tree which stopped the growth but forced the tree to fruit, I'd be scared to do something like that since I don't know what the heck I'm doing

You mentioned you didn't want to prune, but if you're up to the challenge, both olive and avocado can be espaliered. A ton of work, but you can make it grow as low as you want.

I would love to do that this year I've got so much to plant since I just moved to this property but I might consider doing that with an apple or a pear one day. I don't know if I've ever seen anyone try an avocado or an olive that's interesting

"I seen on YouTube a nursery made a complete cut around the cambium layer of a tree which stopped the growth but forced the tree to fruit,"

And this is an almost perfect example of how YouTube can promulgate some really bad information! Cutting through or severing the cambium layer the full circumference of the trunk is known as girdling. And it is a sure fire way of killing the tree!! Yes, it will stop growth......permanently! And any fruiting that may be produced will be in response to the dying tree attempting to reproduce itself. It's a one shot deal at best.

That's funny that's what I thought as well but to be honest I'd have to go back and find the video I can't remember if she completely cut around it or she did a spiral cut around it. Either way I won't be trying it

Inversion grafting differs from girdling in that the bark is not discarded, but rather inverted and placed back on the same location of the branch. This then serves as a throttle or controlling valve to partially restrict the vigor. I must concur that a person should not attempt it unless skilled in horticulture, especially grafting.

here's the video she was using a dwarfing tool. https://youtu.be/45wYnQG9kjE

At $69.00 AU I'll need to take a hard pass on the Cincturing tool. Interesting concept, however.