"Cool as a cucumber"

It is unlikely, in my opinion, that they were referring to growing vegetables.

Good thing that cucumbers are fruit then

I believe the phrase originated from an old poem.

"My passion is as mustard strong I sit all sober sad Drunk as a piper all day long Or like a march hare mad"

Good thing that I a'int a dedicated follower of fashion, then.

^ ain't

' ....... ancient folk knowledge confirmed by science in 1970: inside of a field cucumber on a warm day is 20 degrees cooler than the air temperature.........'