Rakweed

Rakweed is an infectious plant from the planet Raxacoricofallapatorius.

Biology
The Rakweed was a delicacy on Raxacoricofallapatorius, which the natives frequently ate.

The plant is harmless, but if mutated it's dangerous and become then capable of shooting spores. These would go into life forms which are considered 'dangerous' and poison them which would put the being in deep coma which they may never return from. (SJA: The Gift)

History
The Blathereen gave one to Sarah Jane Smith as a gift for stopping the Slitheen, she then reluctantly accepted the plant. She immediately went to scan it using Mr Smith, but apparently he could find no harm in it. Unknown to Sarah Jane, the Rakweed started to mutate and as a result it spread - much to the Blathereen's content. Unfortunately t's first victim was Sarah Jane Smith's son Luke Smith.

The Rakweed was spreading quick around the local area and was spreading in schools, biology teacher Miss Jerome was one who was affected.

The Blathereen became addicted to Rakweed and they would gorge on the food, but Sarah Jane used that to her advantage and blew them up cause the Rakweed was sensitive to sound which was the only way to defeat the Rakweed. (SJA: The Gift)