 SCP-621 is a series of highly invasive flowering plants. These plants, mainly the plant species Didier's tulips, are naturally bioluminescent, powered by water and other nutrients. These plants glow a variety of colors, though most instances glow purple, blue, or green. This bioluminescent effect can be best seen at night, or in a dark area. The effect is only active while the plants are alive. SCP-621, particularly its glow, seems to have a hypnotizing effect on humans, with numerous requests by personnel to store them in their personal offices, all of which have been denied.