English Heritage’s Tynemouth Priory situated on the north east coast at TynemouthCredit:Owen Humphreys/PA Queen Mary, the wife of King George V, called it a noxious and dangerous weed, but garden ivy is posing a far greater threat to England’s castles than the late royal’s famous rose gardens, a conservation charity has warned.English Heritage, which looks after 66 castles from Dover to Carlisle, says England’s castles have survived centuries of conflict, but are facing a “new threat” from ivy and other invasive weeds, penetrating damp and severe weather.It has launched a fundraising campaign to help pay the £1.9m bill for summer repairs, including removing deep-rooted damaging weeds, such as ivy and valerian.“Queen Mary called it dangerous, but like everybody else we think ivy can soften the appearance of our castles in a spectacular fashion, and in many circumstances it’s entirely benign. It stops them getting wet or too cold,” Jeremy Ashbee, head properties curator at English Heritage told the Daily Telegraph.“But, there comes a nightmare moment when ivy turns on you, it grows to such as size and puts down roots into stone work.”The charity has to carry out conservation work on stone work through the year to put right damage done by plant growth, including removing extensive ivy and other plants, shrubs and even trees whose roots are growing into castle wall, which then need to be repaired. Highly skilled stonemasons are used to re-bed loose masonry, and use bespoke lime mortar to repoint an joints that have been wrench apart by strong roots.Penetrating damp and extreme weather can also cause erosion and gradually damage the stonework of castles, said the charity, which is running a crowdfunding appeal as part of its first #LoveCastles summer campaign. It is seeking up to £50,000 in donations from the public to help protect the landmarks for future generations.Mr Ashbee, said: “I don’t want to suggest the castles are teetering on the brink of catastrophe, but many of these sites are in what we call commanding locations, for obvious defensive reasons. Commanding can easily be a synonym for exposed and vulnerable though, including coastal sites, like Tintagel Castle in Cornwall, and on hills were the scour of wind and rain can take its toll over the centuries.”English Heritage said the ivy damage and other weather damage was “unrelated” to this summer’s heatwave, but Mr Ashbee said the charity “understand that this issue will grow as climate change encourages more and more lush vegetation”.He said: “We need to mend the roof while the sun is shining”.The charity is making the call as it revealed more people than ever are visiting its castles, with a record 1.2 million visitors enjoying a day out at an English Heritage castle since the start of May – up 10% on last year.English Heritage chief executive Kate Mavor said: “So far this summer we’ve seen more people than ever visit the castles in our care.”But if these fortresses are to survive for future generations to enjoy, we need people’s help to defend them today – not from sieges or cannonballs but from weeds and damp, the wind and the rain.” English Heritage's Tynemouth Priory situated on the north east coast at Tynemouth Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily  Front Page newsletter and new  audio briefings.