This episode is most definitely from the horticultural canon of LIS, of which there are at least a few.
Things kick off in dramatic fashion when Professor Robinson is pulled by the ankles by a leafy vine into a pit of quicksand. Major West comes to his assistance but is soon dragged in as well. Will comes to both of their rescues.
Smith is again thrown out of the Robinson’s camp. Something about missing detronium canisters. He takes the robot with him. He encounters giant plants and discovers if he places an object inside them it can be duplicated. What he doesn’t realise at the time is that though the duplicates look identical to the originals, they are of poor, flawed quality and soon fall apart.
Meanwhile Judy falls asleep in one of the giant plants. She returns to the Jupiter 2 but it is the duplicate Judy. This imposter is very glum and quiet and acts strangely. Next morning the family wakes up to discover the ship is enveloped by a literal jungle of oversized plants. John and Don proceed to zap them with the lasers.
Judy tries to intervene and in the struggle Professor Robinson finds marks on Judy‘s arm that show she is not the real Judy. They force Smith to take them to the real Judy. They rescue her from where she is still sleep inside the plant and return her to the camp.
Marta Kristen (1945 – present), the Norwegian-born American actress who portrayed Judy, frequently cited this as her all-time favourite episode of LOST IN SPACE since she got to extend herself by playing ‘bad Judy‘.
Twelve years after LOST IN SPACE ended, Marta Kristen appeared in a sci-fi movie called BATTLE BEYOND THE STARS (1980). I remember seeing this film at the cinema because unusually, it featured an actor with a not-so-attractive mole on his right cheek (that would never, ever be allowed to happen nowadays). The film included special effects created by James Cameron, four years prior to him directing THE TERMINATOR.
This rundown of the film is given by British born director, screenwriter and editor Neil Marshall, who amongst other projects has helmed the forthcoming HELLBOY (2019) reboot as well as two episodes of the 2018 Netflix series LOST IN SPACE. Marta Kristen can be seen in a 17 second segment that begins from the one and a half-minute mark where she is seated next to actor George Peppard (1928 -1994) looking at a… hot dog!