Vervoid

Vervoids were a type of artificially created Alien Plant.

Biology
Vervoid were the size of humans, with pink head-like organs surrounded by petals. They could release swamp gas out of their "mouths" when panicked. They had short tendrils at the ends of their "arms", which could function as hands for simple tasks or shoot out poisonous darts. They were covered in maple-tree like leaves capable of regenerating into entire Vervoids if placed in soil. Vevoids grew in pods which were awoken when exposed to higher spectrum of light. Vervoids had short lifespans, living for less then a year until decaying. (DW: Terror of the Vervoids)

History
Vervoids were created by a team on Mogar as a race of slaves. This attempt was not entirely successful. One of the team members was infected by Vervoid pollen, and the Vervoids themselves were genetically inclined towards survival. Instead of serving the humans, they saw the humans as a threat to their own existence. After an accident on the Hyperion III in 2986, the Vervoids were awakened early and attempted to kill all humans. The Sixth Doctor was able to stop them by accelerating their growth rate by using flash grenades to cause accelerated photosynthesis, causing them to die from old age.

Previously, the Doctor's trial had viewed these future events but the evidence had been tampered with by the The Valeyard, prompting him to add a charge of genocide to the Doctor's crimes. The Doctor did not deny wiping out the Vervoids, but maintained he had no other option in order to save the lives of those whom they were attacking. The charge was ultimately not pursued by the tribunal, due to other extenuating circumstances. (DW: Terror of the Vervoids).

Some time between the end of the trial and the Doctor's first proper meeting with Mel (and therefore before the genocide of the Vervoids), the Doctor, Jason and Crystal visited the 'Bar Galactica' in their search for a missing US Peace Envoy. Among the Bar's customers there was a Vervoid. (SP: Doctor Who: The Ultimate Adventure)