The movie is called Deadly Friend. I wouldn’t necessarily recommend taking the time to watch the whole thing just for the gif moment. It is totally ‘80s cheese, if you are into that sort of thing.

Edit: I’m looking at what community I have posted in and realizing I probably could and should have picked literally any scene from Mary Poppins but I didn’t and now you all have to watch a watermelon in a wig explode.

This was 1961 which is definitely not the ‘80s. However, I get your point; practical effects may have been — and were often — jank, but it was real and tangible and I loved it, warts and all.

I thought the singing to plants thing was all about the directly breathing carbon dioxide onto them.