Living as a plant for a year is a fairly high level spell ( base 25 +year, so 45, or 50 if someone is casting it on you). That seems to put it out of reach of junior magi wanting to follow The Path of the Body. Has anyone developed alternate initiation scripts that don't involve living as plant?
The description talks about painful mortifications or fatiguing exertions that last a year. In discussions, we have talked about "working in mine" or living out in the open desert or on a small boat in the ocean for a year as alternative scripts.
Other ideas: long bouts of fastnng, spending the year sick.
Just a thought, but since this spell is part of an established Path with a clutch full of Criamon who are walking it, it's not unreasonable that one of them, over the years, invented the required spell, mastered it, and then made a casting tablet out of it.
Casting tablets are not a universal solution; they inflict a lot of Fatigue and unskilled casters may still not be able to use them. But the required levels of MuCo(He) would be a lot lower.
The rules for casting tablets are in COVENANTS, in the Library chapter.
It's also House Criamon, an ancient and powerful House knowing many great secrets of magic, always searching.
An older Criamon might know of a regio or covenant with Unnatual Law (forget the name of the Boon) that lets this just happen.
"Live a year as a plant" might even be a kind of riddle: There might be a better way to fulfill the inner truth of this than merely transforming into a plant for a year. (A magus who does the obvious might be missing the forest for the trees! Or something like that.)
Another very simple solution, that avoids even the danger of casting a ritual from a tablet, is that the (HoH:MC p.49) Guides of the path know the ritual and cast it at summer solstice on the probationers in the mystic grove, after determining the apt place for each one's existence in the year to come. The probationers need to provide the vis, though.
I could suggest spending a year on top of a narrow column, like Simeon Stylites.
Obviously, the magus would not be allowed to rely on magic to assist in his retreat. Possibly he could use magic to scry and observe his environment, but definitely not to make his situation more comfortable.
The text says a handful of magi have followed this avenue by being transformed into plants. I take that to mean that not everyone following this avenue has done so, which leaves the +3 sympathetic bonus open to some interpretation.
That suggests to me that there are 3 or 4 different initiation scripts available for this avenue. To create a new one, one would need to keep in mind
The Simeon Stylites suggestion is a good one. It would definitely help one develop control over the body, especially if magic was not allowed.