Goosebumps - Stay Out of the Basement
Dr. Brewer is doing a little plant testing in his basement. Nothing to worry about Harmless, really.
But Margaret and Casey Brewer are worried about their father. Especially when they "meet" some of the plants he is growing down there.
Then they notice that their father is developing plant-like tendencies. In fact, he is becoming distinctly weedy - and seedy.