The poem opens mid-thought, with a "But," as if the speaker is answering a doubt we haven't heard. Whatever "it" is, it can't be controlled. Even if you tend it with love and care, it grows into something bigger and wilder: a tree, a jungle, a hive. The poem never says what "it" is, and that openness lets it stand for a feeling, a habit, a relationship, or an action.
The speaker sounds resigned, even a little warning. Love offers no escape ("There is no recourse to love"), because whatever you do will flourish inside you in its own way. What you put out into the world comes back to surround you. The final image is the most unsettling: the wind "whistle[s] your lips," as though you become an instrument played by forces you started yourself. The mood is quiet, uneasy and fatalistic. Growth here feels less like a gift than a consequence you can't undo.