Weird question. Hard for me to word, which has made it impossible to research. I also thing the answer is obvious but I need to make sure.
If I wanted a tree from a seedling to become a bonsai that is, say, 4 feet tall and 4 feet wide, do I grow it out to 4 feet tall and wide immediately and train it accordingly or do I train it as a 1x1 foot tree and over the 15-20+ years (depending on the species, sure) it will expand as it grows and retain the originally trained shape for the most part? My assumption is you train it in the size and shape you want it to be forever. The only growth will be extensions from new growth and width because of age as tress do.
As an aside, I imagine you could have a 1x1 bonsai and decide later to grow it out, but I assume the trained sections will stay the same shape and size forever unless trimmed and reset.
If you want to grow from seed (or seedling) your best bet is to grow it in the ground for a few years to thicken the trunk and periodically prune/chop to produce taper and movement. As far as development and styling are concerned, my teacher (Ryan Neil) approaches it cyclically. You allow the tree to get super vigorous, so it will tolerate a severe styling. The tree is then allowed to regain vigor, which leads to its outgrowing its design. With each subsequent styling, some of what was is removed, leaving behind deadwood and/or negative space to advance the visual age of the tree. So, with each trip around the cycle, the tree attains a more ancient image. It’s important for you to understand that you don’t grow an aged bonsai from a seedling. That would take hundreds of years. You create an image of age by applying bonsai techniques. Also, to keep a tree healthy in the long term, it needs to be allowed to grow between stylings.
Awesome thank you very much!
Growing a tree in the ground or growing containers for future bonsai design is a completely valid approach, as is training slowly in a bonsai container. Each approach has it's own pro's and con's.
If you grow a tree quickly you'll need to pay very close attention to where your cuts/wounds will be. You let leaders (or sacrifice branches) run freely to thicken or extend the trunk and branches as desired.
Growing in a container is slower but more precise and detailed at every step.
With your goal being a 4' tree, I think I would recommend growing the tree out in the ground or growing containers.
Many bonsai are started from nursery material or collected trees which are cut and trained down from much larger material. So this is entirely possible.
One more thing. Your tree will never completely stop growing and expanding. Even after you've reached your desired size the tree will expand at least a little every year assuming it's alive and healthy. So over time it will become larger than you originally imagined. You may want to shoot for a 3' or 3.5' tree and allow it to develop that extra amount more slowly over time.