Trees don't grow to the sky

I came across this phrase. I admit to do little searching on it just a quick google.
The websites didn't make sense and here I am. Trees do grow to the sky where else would they grow? If you were a giant sure they wouldn't grow to your sky but to a rabbit yes they do. I just find that a bit annoying and yeah I am being preachy. Post a comment if your not happy or would like to shed some light on this phrase.