I've been thinking how best to answer this question ever since you posted........it is not exactly straight forward :-)

First, all named cultivars of Japanese maples are grafted......or almost always. The shoots of the desired cultivar are taken from the parent tree as cuttings and then grafted on to a seedling species JM. For upright trees (like Bloodgood), the grafts are typically about 6-8 above the root flare but can be higher. Usually not lower - low grafts are typically reserved for the weeping forms like most dissectums. Grafting is done while everything is very tiny - really just seedlings.

Part of the appeal of Japanese maples is their often very sculptural natural growth habit. This can sometimes be enhanced by pruning but is seldom created by pruning. A great deal of this sculptural quality is determined with the selection of the tree at a young age, looking for attributes like low branching or interesting bends. And then you make the most of those going forward both through training and very selective pruning.

thanks a lot for the explanation.

I had been very curious about these JM. Smaller JMs for sale in the nursery or homedepot never had that kind of great shape. I tried to imagine how these smaller JMs could be pruned/trained to grow into the great shapes shown in the big boxes.

From your explanation, seems that I cannot never expect those smaller JMs grow into those beauties in the big boxes.

where can I buy these grafted JM with good potential to get the shape shown in my picture?

I also see some articles about propagation by cuttings. is that true that they won't get good shape easily without grafting?

thanks again.

Small trees often grow into larger trees with interesting sculptural growth habits. It's just a matter of doing a lot of looking for the right tree with the proper potential. And knowning how to do some careful training and judicious pruning. Afterall, that is how bonsai is done and tiny little JM's that are bonsai'd typically display this very sculptural quality you are looking for.

IOW, achieving that type of form takes time - you will not find it in the smaller trees simply because they haven't been around long enough to develop that growth habit. Better retail nurseries that specialize in JM's would be a good place to start the hunt and should have personnel that can help you choose for this effect. Forget places like HD and the other box stores - they buy cheap and in huge quantities and are not looking for special or unique features.

JM's are difficult to propagate from cuttings. That's why all the quality, named treees you will find have been grafted.