Malcolm - I found it on You tube ! No, it wasn't staged. There's notes elsewhere confirming this and you can clearly see him losing his footing , first in the rear view camera and then [ look at the expression on his face ] in the forward camera. He does come a hefty old crash on his back at the bottom of the hill.
You Tube : 'Columbo falls down hill'.
Looks like they edited his reaction . The man's a trooper !
if you can watch this without laughing - check your pulse.
4/5 of years ago...pre Netflix etc...I was remembering that stumble and was trying to find it...to my amazement it came up as 'Columbo hill" on Youtube...and was one of the very first Columbo scenes I shared with my then 8/9 yr old daughter...we howled with laughter and still do.
"the quickest way down"...lol
having said Greenhouse Jungle is a major stumble in and of itself....terrible episode in my opinion...but I digress