Varga plant

Varga plants were deadly plants native to the planet Skaro. "Varga" literally meant "devourer". (AUDIO: Purity, Masters of Earth)

Biology
The most common variety of Varga plants resembled large cacti, but with roots that allowed them to drag themselves along. They had the ability to poison other creatures with their thorns, making them into other Varga plants. An infected victim would first become homicidal. As the infection progressed, white hair would grow over their bodies. (TV: Mission to the Unknown) As the toxin infected a person's system, they would hear a voice calling them to join the Varga and kill. Proximity to the plants meant their influence was greater; they could even feel Varga plants if they were in pain. Transformation into a Varga depended on the severity of the wounds inflicted. (AUDIO: Masters of Earth)

Another variety of Varga plants, which infested Kaalann, was different in appearance, being more akin to a Venus flytrap and immobile. Their venom also killed with a touch. (GAME: City of the Daleks)

The spines could not penetrate the thick hide of a Slyther. (COMIC: The Only Good Dalek)

By the Last Great Time War, Varga plants possessed regeneration inhibitors which could kill a Time Lord instantly. (AUDIO: Legion of the Lost)

Varga extract could serve as a "surprisingly passable" substitute for tea. According to the Eighth Doctor, it was the only way to make tea on Skaro. (AUDIO: Palindrome)

History
Varga plants existed since very early in Skaro's history. The name "Varga" meant "devourer" in the Dal language. Originally they could not move; instead they would wait until their prey approached them. Later, due to the chemical and radiological pollutants released into Skaro's atmosphere and environment during the Thousand Year War, they began to mutate so they could move. (TV: Mission to the Unknown, AUDIO: Purity)

Fifty cycles after the Thal-Dalek battle, Varga plants had begun to grow around the abandoned Dalek City. (AUDIO: Return to Skaro)

The Dalek Empire later imported them to other worlds. They were used during the 22nd century Dalek invasion of Earth when they planned to turn the entire planet into a warship from which to shower other worlds with Varga seeds. (AUDIO: Masters of Earth)

When the Daleks set up a base on the planet Kembel in the 40th century, they brought some Varga plants with them to act as sentries in the jungle surrounding their base. Jeff Garvey and Gordon Lowery, members of Marc Cory's expedition team, became infected. (TV: Mission to the Unknown)

The plant was again found on a terraformed Jupiter where the plant infected a large battalion of Earth Alliance troops. (AUDIO: Dalek Empire II: Dalek War)

Varga plants were utilised on Vildar during the Last Great Time War. Collis died after touching one of the plants. The War Doctor was able to destroy the batch after the fact. (AUDIO: Legion of the Lost)

Following the Time War, Varga plants infested the ruined Dalek capital city of Kaalann. Though these could not move themselves, they had long, snapping "mouths" which excreted jets of venom. (GAME: City of the Daleks)

When the operators of Station 7 took a section of petrified forest from Skaro, they took some Varga plants with it. These plants were similar to the ones used on Kembel, but possessed arms and legs, rendering them capable of full movement. Hadleigh fell victim to them, as well as two members of Gamma Team. (COMIC: The Only Good Dalek)