Krynoids are a type of alien found in Doctor Who and the main antagonists of "Seeds of Doom", they are parasitic in nature and often referred to as "galactic weeds" : due to the volatile nature of their original world many Krynoid seeds fly across space, where they stay in hibernation for thousands of years at a time.. once they land on a planet they infect native animal life in order to create hosts and can even grow massive "adult" versions of themselves.