Other thread, same topic :-)

https://www.houzz.com/discussions/5836080/put-a-round-peg-in-a-square-hole#24896673

Sorry, didn't see it

That's not how I read it. He debunks round holes and explains why, adding that it would be even worse if amended. Then he goes on to suggest square holes and no amendments.

Read it again.

He's combining two separate methods. If you use a round hole and native soil to fill, there won't be roots trying to follow the enhanced soil around the curvature of the hole. So how can he say it's even worse when amendments are added? His whole theory depends on there being amendments. Didn't you catch that?

Totally flawed.

Roots don't follow hole walls unless these consist of something like solid rock or intact concrete. No, the main problem with amending of back-fill is how the movement of water into, through and out of the hole is likely to be affected.

If the tree is properly planted, without amendments, the shape of the hole is a non-factor.

Exactly what was said over in the other thread linked to above.

No Bill, I didn't catch that. And I still don't. I've read it several times. We'll just have to disagree on his meaning. I have contacted James Wong for a reference for the research he quoted. I'll let you know if I get a reply.

I guess if one has to amend the soil when planting, it is better to dig a non circular hole. I can imagine instances where not amending the soil while planting would be more detrimental than the eventual limitation of roots circling due to the amendment creating disincentive for the roots to grow beyond amended soil.

floral,

I wasn't meaning to be disrespectful and not necessarily disagreeing.

Here's what J. Wong says: ' But here’s what happens to the tree’s roots when you plant them in a round hole, '

Okay, that's one thought, correct? And it covers a round hole, just a plain old round hole without amendments. How else can you read that?

Then he continues: especially one filled with lots of rich compost and fertiliser,

So he's a bit ambiguous, imo, on what exactly he meant but it misled me to think he meant 'any hole' will have circling problems but amended holes would be worse.

I don't think it matters much what the shape of the hole is. And I think if you amend the soil the newly planted seedling gets a good start. Gets a chance to recover from the stresses it's received recently. Eventually that seedling is going to have to live in the soil in its new environment. If the shape of the hole matters then maybe you should also investigate oval holes.

From my own experience the roots spread out into my hard packed clay.

Some of my round mulched areas end up triangular or square after I mow past them a few times in straight lines.

Far as the holes go, mine end up irregular round. I'm sure I've forgotten to break up the smooth edge to my holes before. I figure not measuring to a precise circumference might make up for that :)

Brilliant idea! All else being equal, digging a square hole rather than a round one will reduce root girdling risk...without much added effort. Sounds like a win-win. Common sense, yet not standard practice for some reason?

" yet not standard practice for some reason? "

Because there is no real logic or science behind it. Root girdling is not caused by the shape of the planting hole. Too long in a too small or restricted a container OR too small a planting hole (regardless of shape) in compacted soil conditions are typically the causes, as well as planting too deeply. Dig a generously sized but fairly shallow planting hole of whatever shape you prefer and plant with a properly loosened - and preferably bare rooted - rootball and you will have no concerns about girdling.

Amending only improves results when the entire rooting area of the plant is amended and this amending remains in effect during the entire span of the planting. In other words it does make sense when growing short term plants with limited root systems, like flowering annuals and annual vegetables. Ones which are also being grown in beds that are frequently re-amended. Or in the case of making special beds for small alpine or succulent plants, where mineral materials like sand and gravel are used to increase soil aeration - and these materials are never going to decompose and disappear.