Ray Milland makes an excellent adversary for Columbo. In The Greenhouse Jungle, he proves he could chew the scenery with the best of Hollywood. Columbo's "partner", Sergeant Wilson (Bob Dishy), is one of the few comic relief type characters I've ever seen that is really funny. The rest of the supporting cast is also quite good.
The way Columbo solves the murder in this one is truly surprising. Even though the clue that leads to the resolution of the murder is in plain sight, I didn't realize what it was or even why it was in the movie. It's a notch above the normal Columbo fare.