A report commissioned by protestors has identified a number of rare plants living in the wooded grounds of Greystones, Darlington.
Campaigners asked Darlington-based David Green to conduct the survey.
The most significant finds were among 78 types of woodland flora, one of the most exciting being tall tutsan, a type of shrub originally from Madeira and which has only a scattered distribution in Britain.
Mr Green said it had not been recorded in County Durham or adjoining counties.
He also recorded rarities including wild daffodil, stinking hellebore and stinking iris, and said Greystones was one of only two places in Darlington where the stinkhorn fungus has been recorded.
There were five types of moss, two of fern and eight fungi.
Mr Green logged 26 types of invertebrate, including southern hawker dragonflies, and three types of butterfly.
There were also seven-spot ladybirds, which are the subject of a national Wildlife Trusts survey launched in response to a drop in numbers.
Mr Green's report included 20 species of bird, ranging from sparrowhawk and tawny owls to less common creatures, including great spotted woodpeckers, crossbills and the tree sparrow, which is the subject of a national campaign by ornithologists to arrest a decline in numbers,
There were three types of mammal, pipistrelle bats, grey squirrels and hedgehogs.
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