I was at a local club auction this past summer, I picked up this massive Black Locust. I have not seen another like it. It was collected a few years ago and will be ready for a pot this spring. Has anyone worked on this species before? I have been just letting it grow and have done a little wiring this fall. Any help on how to treat it would be helpful
What is the climate where you live? Black Locust have compound leaves and large spikes.
You have the advantage of having your hands on the tree. They are very hardy in the mid western USA and have been used as fence posts that have lasted for a century. They tend to live in limestone rich areas, so would tolerate soil that is alkaline.
The base looks beautiful! If the leaves have dropped I would love to see the branch structure.
Good find!
I am in 6a/6b. Same with us here, fence posts and great wood for the wood burner. Yes it does have compound leaves and some very nasty thorns (speaking from experience) here is the tree once the leaves fell and wired.
Beautiful little guy! The tree would benefit from being in a broader shallower container to make root pad flatter and finer. Just a suggestion for future finds! I love to put finds like this in an Anderson flat or wooden grow box with lots of drainage and air circulation. You can also punch or drill holes into the bottom and sides of the nursery contain to improve oxygen available to the roots. 
There is a grove of black locusts behind my house, and so I get a lot of donor seedlings every year. But none are as developed as this. Most are still pencil thick (or smaller).
Prickly little devils, but definitely have the potential to be great.
I think I will take your advice and build a box for it, seems like the best way to reduce the root mass, and build finer roots for a bonsai pot.
They can be fast growers in the right conditions but have a weird tendency to drop primary branches on a whim every once in a while. I had a near miss accident with such a primary branch fourteen years ago. I wonder if that could be controlled through regular pruning.
