Alt Text: Panel 1: Two women sit in a living room surrounded by plants, drinking coffee. One says "It's true!" Panel 2: She continues, "Plants grow faster when you play them classical music!" Panel 3: The leaves of a potted plant are reaching towards the window "Must... flee... from... this... torture..." Panel: 4: The woman continues, "I even put on classical music when I'm not home." The potted plant in the foreground has a thought bubble that reads, "...kill... me..."
My guess is the loud bass vibrates dust particles that might clog up pores loose, or maybe helps with nutrient flow inside the plant. Like it's affected by sound not music.
Though music might be generally better than most loud sounds because it's one of the few cases where sound can be loud but isn't also associated with something that adds more dust to the air, which might even give a net negative result.
Mythbusters experiments all suffer for low sample size and correlation not being causation. It's a fun show for kids to watch, but has no scientific merit.
I mean, you only need an n of 1 to prove that you shouldn't drive a school bus behind a 747.
I wouldn't say zero scientific merit, but I do agree that some of their conclusions were overly strong. The "plausible" option really helped, rather than everything needing to be confirmed or denied.