Hello, if I'm trying to encourage trunk growth on a plant, is it generally better to let the plant grow in the ground or large pot before trimming and transplanting to a bonsai pot or to continually transplant to larger bonsai pots when they plant is ready? Any info/advice is much appreciated. Thanks!
If you have the ability to plant it in the ground, that is your best bet. If you can not grow in the ground easily you can use large nursery pots, or anderson flats, or other larger containers to grow out the tree to develop a trunk.
MOST bonsai spend the first 5 to 15 years growing large to develop the trunk. ''Bonsai Training'' does not start until the trunk is just about the diameter desired for the finished tree. At this time the tree may be 10 or more times taller than the planned finished bonsai. Once the training begins, there will be very little increase in the trunk diameter.
I have an Amur maple, I would like to have it be a shohin tree, less than 8 inches tall (20 cm) with a nice 2 or 3 inch diameter trunk (5 to 7.5 cm trunk) Right now it is over 6 feet tall (over 2 meters) and it is growing in a large nursery pot. I will not cut it down until the trunk just above the soil is 2 inches diameter. (5 cm diameter).
There are variations on this approach, but in general, you let the tree get large in order to develop the first few inches of trunk.