This is a predicate adjective, as it immediately follows a copulative (=linking) verb "to grow". If it said - The tall grass, then "tall" would be nominative. This way it isn't, it is a predicative adjective.
Answer:
The author wants to show that even though the Monkey King thinks he is an important ruler and is equal to the others, the other deities just consider him a monkey (and he might not be as important as he thinks he is).
Explanation:
The magic shoes from the relative location of geography
