Krynoid Krynoids were large , carnivorous alien plant s that could be thought of as galactic weed s . On planet s where the Krynoid took root , all animal life would become extinct , as Krynoids desired that all plants should win against the animals that ate them . Biology . Krynoids travelled through space as tendril s in small pods , always in pairs . They were very hardy and could easily withstand the extreme cold of space , ( TV : " The Seeds of Doom " ) although snow and ice could still slow them down and render their pods inert . ( PROSE : " An Apple a Day . . . " ) A Krynoid itself was bulky , covered in tendrils and vine s , some of which ended in red flower - like structures . They had an undefined anatomy with no front or back . Though they had great tolerance for cold , high temperatures could damage them . They required animal protein s while young , but could survive on normal photosynthesis later in life , and gathered nitrogen directly from the air without a need for roots . Over time , Krynoids were also able to channel their power into other plants , at least within a mile radius ; they were also able to psychic ally possess other humans , though this may have been due to some humans ' sympathy for plants . While they were unaffected by gunfire and laser s , they were affected by being cut as well as fighter plane missiles , ( TV : " The Seeds of Doom " ) and could be killed with special rockets . ( COMIC : " Don ' t Step on the Grass " ) Krynoids couldn ' t live in environments with high carbon levels . ( PROSE : " The Taking of Chelsea 426 " ) One strain of Krynoids were affected by high - pitched noises , allowing the original consciousness of their host to reassert itself temporarily . ( AUDIO : " Hothouse " ) Life cycle . Krynoids started life as small pods about twenty centimetres in diameter . Possibly due to the volatile nature of the Krynoids ' home planet , many of these pods were launched into space , always in pairs . These pods could survive long trips in space , hibernating for thousands of years . Once a pod reached a planet and was exposed to sunlight and more tolerable conditions , it grew . When a creature came too close to the pod , the pod would release a long shoot which grabbed and infected the victim , slowly turning it into a Krynoid . The transformation began almost immediately : first the skin turned plant - like in colour and texture , then it looked covered in green tendrils . Finally all but the basic shape of the lifeform was lost under a mass of green , vegetable growths . The body temperature and the pulse rate dropped severely and plant bacteria — schizophyte s — appeared in the bloodstream . ( TV : " The Seeds of Doom " ) If a Krynoid did not find a host , it could also take root in the ground . ( AUDIO : " The Root of All Evil " ) The Krynoid took over its host ' s mind first . By the time the body had completely changed into vegetation , the host ' s mind had given way to the Krynoid sentience . Initially , the shock of this transformation kept the hybrid sedate , but once the Krynoid had taken over fully , it became mobile again . It seemed to have great strength . During this early period , the animal - Krynoid hybrid was desperate for warmth and protein , which it absorbed as it converted its host . As it ate , it grew larger . The Fourth Doctor theorised that amputating the area first infected might slow the rate of infection , but this was never put to the test . They could grow incredibly quickly , easily outgrowing a house in a few hours , and within a day the Krynoid would reach its full size , becoming as large as St Paul ' s Cathedral . Finally , the Krynoid entered its germination period where it would release hundreds of pods , reproducing a thousand - fold until Krynoids covered the entire planet . ( TV : " The Seeds of Doom " ) Krynoids could grow to thousands of metres tall , poking through a planet ' s upper atmosphere . This allowed them to discharge seed pods into outer space . ( AUDIO : " The Root of All Evil " ) Intelligence . The Krynoid ideology was directed towards the revolution of all plant life against the animals that ate them and depended on them to live , believing " the plants must win . " A Krynoid seen on Earth in the 20th century could speak English and attempted to bargain with humans for their lives . It spoke of its host as being part of the Krynoid , referring to " us " and " we " . ( TV : " The Seeds of Doom " ) Hosts being consumed by a Krynoid would hallucinate about being in a jungle or rainforest and would begin to feel a part of it . ( AUDIO : " Hothouse " ) Krynoids possessing humans could not describe concepts unless their host knew the right words . ( AUDIO : " The Green Man " ) A Krynoid that took a wolf as its host was unable of speech . ( AUDIO : " The Green Man " ) History . The Krynoids were well known throughout the galaxy , though difficult to study because of their violent nature . Incursions on Earth . Krynoids apparently had been seen in Britain prior to the 12th century , as carvings of a " green man " made of plants existed in a Catholic Church . During the reign of Richard I of England , two Krynoid pods were activated in England and laid siege to a castle . One , taking a local medicine man as a host , was defeated by the Knights Templar wielding axes and its remains burnt . The other , taking a wolf as its host , was defeating using boiling oil and gunpowder created by Moses of Tyre . ( AUDIO : " The Green Man " ) Two Krynoid pods arrived on Earth in Antarctica approximately twenty thousand years before the 20th century . They lay dormant until the 1980s , when one of them was discovered by a scientific expedition . This pod hatched after being thawed out by an ultraviolet lamp . It infected Charles Winlett , one of the human scientists who had found it . The Fourth Doctor , having been alerted to the situation by the World Ecology Bureau , went to the base and investigated . He found the second pod . The second pod was stolen by Scorby , who destroyed the base and the Krynoid with a bomb and took the pod to Chase Mansion , botanist Harrison Chase ' s home . Chase allowed the pod to infect one of his scientists , Arnold Keeler . This second Krynoid grew to gigantic size and developed a psychic link to Chase , who agreed with it that plants should be dominant over animals . The Krynoid was destroyed when UNIT bombed the mansion in an aerial attack . ( TV : " The Seeds of Doom " ) UNIT kept information on these Krynoids in the Black Archive s ( COMIC : " Don ' t Step on the Grass " ) and pods were kept in the Vault . ( AUDIO : " Tales from the Vault " ) The Eleventh Doctor once saved the actor Peter Davison from a Krynoid . ( COMIC : " The Girl Who Loved Doctor Who " ) At some point around the end of the 20th century , two Krynoid pods landed in a field in Yorkshire . One took root in a farm field , overtaking and choking the crop ; the other infected the farm ' s owner . The Krynoids were blown up with Diesel fuel by Eve Black and a local policeman . ( AUDIO : " The Root of All Evil " ) In the 2010s , former musician Alex Marlowe led a project attempting to genetically engineer a new Krynoid strain that would cause the physiological changes induced by the Krynoid infection to still take place , including granting the power to control plants , while keeping the victim ' s original consciousness intact . The project was a failure . It produced a type of Krynoid with a far higher metabolism . It completed its life - cycle in a single hour , not the day normal Krynoids took . Fortunately , the new Krynoid strain had an unexpected weakness in that high - pitched sounds , rather than just causing it pain , allowed the victim ' s consciousness to re - assert itself for a brief period . The Eighth Doctor was able to exploit this weakness and destroyed Marlowe and his new Krynoids . ( AUDIO : " Hothouse " ) A Virgoan space probe had an encounter with a Krynoid on Melandra IV , which resulted in it bringing the Krynoid to 21st century Earth . ( PROSE : " Stop the Pigeon " ) The Twelfth Doctor recalled dealing with a Krynoid for Hyphen T Hyphen . ( COMIC : " Space Invaders ! " ) On Trenzalore . A pair of Krynoid pods landed on the planet Trenzalore . The Eleventh Doctor speculated that " someone " had sent them to Trenzalore . One of them lay inert in the snow , but another fell into a climate - controlled orchard inside a greenhouse , and subsequently hatched and infected the farmer Pieter . The Krynoid grew to the size of a barn and fed on live animals in its aim to colonise Trenzalore and consume all animal life . The Doctor and his companion Theol Willoughby drew the Krynoid to the Clock Tower in Christmas , where one of Christmas ' townspeople , Jerl Tompkinson , used a rubber hose to fire water at the Krynoid , freezing it . With the Doctor ' s help , the townspeople pulled at a rope to ring the Clock Tower . The reverberations from this noise shattered the Krynoid ' s frozen body . The Krynoid ' s — and Pieter ' s — remains were burnt on a makeshift funeral pyre , along with the unhatched pod . Theol carved the Doctor a walking stick out of a piece of Krynoid for the Doctor to remember Pieter by . ( PROSE : " An Apple a Day . . . " ) On Gallifrey . When Handrel was trying to give himself unlimited regeneration s , he used a Time Scoop to capture a Krynoid for research . ( PROSE : " The Time Lord ' s Story " ) Other universes . In a universe where the Doctor worked with a " new version of UNIT " after he was exiled to Earth in 1997 , " an annoying man " tried to infect the United Nations with Krynoid pods . The Sixth Doctor and Evelyn Smythe accidentally travelled to this universe and helped the exiled Doctor save the UN . ( AUDIO : " The 100 Days of the Doctor " ) Other references . After suffering from memory loss , Sarah Jane Smith could not tell the difference between Krynoids and Pescaton s . ( PROSE : " Interference - Book Two " ) The Tenth Doctor compared the swamp monster s to stage tree s , comet flower s and Krynoids . ( PROSE : " Wetworld " ) He once thought an occurrence of hostile plants was caused by a Krynoid . He was proven wrong . ( COMIC : " Don ' t Step on the Grass " ) He later worked out that the Spores , which turned out to be Rutan s , were not Krynoids . ( PROSE : " The Taking of Chelsea 426 " ) When the telepathic Emily Fairfax read the mind of the Hypothetical Gentleman , a Krynoid was among the images she saw . ( COMIC : " Hypothetical Gentleman " ) Behind the scenes . The humanoid Krynoid costume was a modified Axon costume painted green . Ironically , plans for a collect - and - build Krynoid toy were abandoned and the Krynoid toy was instead painted orange and pink and turned into an Axon toy .