I'm trying to make a spell in order to heal a damaged plant (not to ensure it grows in a correct way nor enhance its growing) just heal it.
In the core rules the guidelines especify that it is possible to heal a plant using CrHe but no further details are given about the levels. A possibility is to use the levels to heal a human (CrCo) or an animal (CrAn). But the levels for creating an entire plant and creating a human corpse or a mammal are quiet different (the plants are easier) so I think it is not a correct way.
Check the difference in levels between creating and healing, and apply that to plants. Serf's Parma (at work)
Lets say its level 15 to create an animal and level 10 to heal it. It it says level 10 to create a plant, then level 5 heals it. Numbers are way off, but I think you get what I mean.
Thanks for the comment, I have tried to put it in practice.
I have take as reference the CrAn guide, the herbam spells are far more simple than their Animal counterparts. Finally I have taken an effect that exists in both tables and apply the difference in magnitudes to the healing effects in animals.
The guiding effect is the creation of an individual that is included in both forms:
CrAn 15 -> create a mammal
CrHe 1 -> Create a plant
The difference (in magnitudes) 15 – 1 is 6 magnitudes.
The levels to heal a plant will be (the equivalent levels in corporem are also included in order to see the cost difference):
So the equivalent to the “Chirurgeon's Healing Touch†CrCo 20 will be:
The healing plant CrHe 2
Range: Touch Duration: Momentary T: Individual, ritual.
Heals a light wound from a plant being touched. This spell does not heal levels from poison or disease.
(Base 1 +1 Touch)
We have to take in account that the base size for herbam spells is a plant roughly one pace wide in each direction. Since the base animal size is a +1 (a pony). The necessary modification should be done to heal a great plant (by example an oak).
However there's a drawback in that it's a ritual, and all rituals must be raised to at least level 20 after the calculation.
Thus, it's pointless to design that spell as written, it would still be learned/cast as a level 20 spell. You might as well include the size (or possibly group) modifiers to raise it to a level 20 spell, to get the full benefit out of the ritual nature. (pg 114, ritual spells)
I'm not sure what a "Light Wound" to a tree would be. I don't think many plants/trees are defined in any typical such terms, even if they are "monsters". You can hack almost half the trunk out of a tree, and it may still live - doesn't work the same way "animals" do.
With darloth's point about the minimum level for Rituals in mind, and your own about the diff between an individual "plant" target and an oak tree, maybe something like this:
CrHe 20 Herbem Restorative
Range: Touch, Duration: Momentary, T: Individual, ritual.
Heals any plant or tree, up to the largest of natural trees, of all damage and natural ills, restoring it to full health. Wounds will be sealed over, but missing parts will not be recreated. Magical ills may be healed but will not be removed.
(Base 5, +1 Touch, +2 size.)