It does seem to me to be a part-time profession up North, due to the fact that you can design, but you sure can't install your designs for at least half the year. Any ski resorts nearby where you could work in the winter? You'll be worked to death in the spring and summer, though.
Down here, where it's possible to garden year 'round, you can make a living at it.
As for Hort. Therapy, I know several Master Gardeners who work on different programs like that, one for troubled teens, drug recovery etc. and another for older people with depression.
