Here's why:
* Infinitives are the base form of a verb, usually preceded by "to".
* They can act as nouns, adjectives, or adverbs.
In the phrase "to grow", it functions as a noun.
For example:
* To grow is her greatest desire. (Noun acting as the subject of the sentence)
* She wants to grow her own vegetables. (Noun acting as the object of the verb "wants")