Columbo S4E3 “By Dawn's Early Light” (1974)
No ferns spotted! However, this episode is remarkable in many other ways. For one, it stars Patrick McGoohan, well-known for his role as Number Six in The Prisoner, as a no-nonsense commandant of a military academy. He won an Emmy for his performance in this episode and went on to act in and direct several episodes of Columbo.
Secondly, it was shot on location at Citadel Military College of South Carolina ("The Citadel"), well-known for being sued by Shannon Faulkner, a high school student who applied to the at-the-time all-male college by hiding her gender on her application. She sued for the right to be admitted, and won, but wound up quickly leaving because of the abuse she faced on and off campus.
Lastly, this episode features a vanishingly rare sight of Lt. Columbo sans raincoat and, indeed, sans shirt. You're welcome.