Tohl Narita: “It is very hard to design plant monsters. At any rate, I designed it based on the cactus with its balance disrupted.”
While it seems to have been said that the costume of Green Monse was modeled by Kaimai Production led by Eizo Kaimai who used to be with Toho as a sculptor as his production company was largely involved in the monster costumes production for the tokusatsu TV shows in the 1970s including “The Return of Ultraman” and “Mirrorman.”
According to a recent book interview, Kaimai himself denied it and revealed it was made by the Toho art crew including himself back then: Teizo Toshimitsu, Yagi brothers and Eizo Kaimai to be more specific.
Therefore the Green Monse costume was made through the same process as the Toho monsters: forming the costume with urethane and latex on the fabric pasted over the core made of wires and then removing the core finally by squeezing it (the rough surface was made of sawdust mixed with latex).
He says, although it was supposed to be stuffed with urethane on the set, the costume is likely to have been used as it was without the stuffing and it made the monster look rather thin.
According to Toshihiro Iijima who directed this episode, as the costume was first used to shoot the special effects scenes (including the battle scenes), it looked untidy with its bottom part rubbed off when it appeared for drama scenes with humans.
After that, it is said that the costume was set ablaze in real life for the ending scenes which showed the monster burned up after being shot by Spacium Beam.
It makes me feel a bit sad to find Green Monse seems to have been unduly treated (even with lack of nice pics) while I quite like the amorphous-intended monster designed by Narita.