Mammoth Flower (マンモスフラワー Manmosu Furawā) is the fourth episode of Ultra Q.
A strange disturbance in Tokyo upturns the ground and shakes the buildings as if something huge is moving beneath the foundations of the city. In the canal of the Imperial Palace, a large tentacle-like vine called Juran appears, frightening passersby. Following this incident, Jun, Ippei and Yuriko witness an underground attack on humans, as the vines try to suck blood from their victims. Dr. Ichinotani suspects that a giant plant has taken root beneath Tokyo. Soon afterward, the monster-plant's bulb crashes upward through a building and the mammoth flower blooms over the city. While Ippei tries to rescue a friend from the devastated building, Jun flies Dr. Genda high above the mammoth flower in his Cessna. The scientist drops a special device that showers carbonic acid gas upon the giant plant and it is destroyed.
Ultra Q Volume 1 features episodes 1-4, while the Total Natural Color Blu-Ray features episodes 4-7.