when does doofenshmirtz mention not having a green thumb?

Dr. Heinz Doofenshmirtz mentions not having a green thumb in the "Phineas and Ferb" episode titled "Ferb Latin." In this episode, he expresses his lack of gardening skills while discussing his failed attempts at growing plants, which leads to humorous situations. This line reflects his character's self-deprecating humor and tendency to struggle with everyday tasks.