Unorthodox Enchantments for Moving a Ship

It's dead tree, not a living one. That might make it harder.

The Size modifier is far worse than the Treated or Finished modifier. Ships are pretty big.

They certainly are.

Something that I would like to add, with the caveat that it is a ruling from our game and not RAW. My group limits the possibility of having Intelligence to living plants, while dead/processed plants are limited to Cunning.

It's a shame you put the shade to rest, you could have had it animate the ship.

Read ArM5 p.137 box Muto Herbam Guidelines

Level 4: <...> Awaken the consciousness of a plant.

Compare this to the other guidelines there, which refer to "a plant or item from a plant".

And then compare this with Aristotle's plant soul:

The souls of living beings are ordered by Aristotle in a hierarchy. Plants have a vegetative or nutritive soul, which consists of the powers of growth, nutrition, and reproduction.

These souls are not immortal. A dead plant has none.

(ArM5 p.80) The Limit of the Soul has

Hermetic magic cannot create an immortal soul, ...

and (A&A p.31 The Human Mind has

The principle difference between the mind of an animal and that of a human is the possession of a soul, which is unique to rational beings such as humans, angels and demons, The souls provides both reason (ratio) and intellect (intellectus).

To summarize: Hermetic magic cannot create an immortal soul, and hence no reason or intellect. The best it did so far is mutoing an already existing Aristotelian soul of a living plant (ArM5 p.137 Stir the Slumbering Tree) "into a state of consciousness resembling that of a human".

So your troupe follows the rules pretty closely.

Some groups would rule that the plant must be living for the effect to be used on them at all. Over the years I have seen people argue on both sides of this.

My current group, or more specifically my character since he is the one who does the vast majority of things based on that effect, was actually originally only using the effect on living plants. It was another player who actually brought it up for discussion because of something he wanted to do. That is when we collectively looked at it and reached our group conciseness that Live Plant = Int, Dead/Processed Plant = Cun.

Awaken a massive plant, bind the awakened spirit into the tree as you kill it, using it's own corpse as the binding item. Turn it into your mast.

Go big.