Yesterday, on an impulse, inspired by the Bob Ross of bonsai, I dug up two maple seedlings from my property and potted them. I had only one bonsai pot, so for the other one I had to use what I had on hand. (I did have a couple of flowerpots, but the drainage holes were so big that the bonsai soil fell out.) Behold:
They survived the night, which encourages me. Can I make these things into "real" bonsai? If so, what's the next move? (And how long can I use that Styrofoam cup as a pot?)
Haha, Bob Ross of bonsai is a good comparison! He knows what he's doing by the way, I have seen some of his videos on that channel.
Your approach could work, however it is not the fastest way to get a nice bonsai tree. I mean you can keep the tree small from the beginning (like you do now), but it would take decades this way before the stem would be impressive in thickness and would look like a real small tree. This is because the container keeps the plant small (no room for roots, so no optimal resources to grow). A trick what most bonsai growers do (Peter Chang included), is to let the seedling first grow for 5 or so years in larger containers. They will have plenty of room for their roots and grow thick stems this way. They will also grow in length, but that is something you'll have to prune later on. The larger the plant gets, the faster it will grow. Then, after 5 years, prune them into bonsai and put them in your nice bonsai pot. The stem is then impressive already and give it a few more years of shaping and pruning, and it will look like a miniature tree.
Another trick is to choose a species that has not so large leaves, because the smaller they are the more they are in the right proportion with the small tree. Don't understand me wrong, in principle every tree can be used for bonsai, but the larger the leaves the more difficult it is, and your Acer pseudoplatanus (in your bonsai pot) is one of the most difficult ones to bonsai. It is very hard to get these leaves to become smaller.
Don't let me discourage you, a nice thing with bonsai is that you will learn to be more patient...
I have been doing informal bonsai on Acer Ginnala, the Amur maple. They seemed a good choice as the leaves are already small and it is a tough tree that provides many, many seeds.
You can keep them in a styrofoam pot or similar for years. In order to keep them from drying out I keep them in my pond. They bottom of the pot sits in water and they grow roots into the water. I don't even bother overwintering by digging them in anymore. They spend all year in a site exposed to winds and -30 Deg Celsius temperatures but with good snow cover.
In bad years the rabbits eat the tops which adds to that old and gnarly look that is popular.
The goods news is the leaves colour up nicely in the fall but the bad news is that there is no reduction in leaf size which is a prerequisite for a really good bonsai.
So, they can be a lot of fun for informal bonsai.
