Leylandii, also known as the Leyland Cypress, has steadily grown in notoriety through the twentieth century. Planted as a screen, it will grow at an extraordinary speed to create hedges as high as a hundred feet tall. For those who wish to create total privacy this has been an enticing prospect. However, most people don’t want vast hedges overshadowing their garden, and the species has been responsible for some bitter disputes between neighbours, including some which have spilled over into violence and even murder.
Extraordinarily, Collins Tree Guide defines leylandii as ‘the most planted and the most hated garden tree’ in the UK. This is because it has too often been grown without due care and attention, and even for those owners who do wish to keep them under control, the cost of trimming a fully grown leylandii hedge can be an obstacle. Leylandii are greedy drinkers, taking the moisture from surrounding soil, and as a foreign import, they don’t even harbour much of our indigenous wildlife. In many respects they are the anti-hedge, a pariah in our ‘green and pleasant land’.
The bastard offspring of two types of cypress native to North West America, leylandii was first cultivated by C. J. Leyland, a nineteenth-century ship’s captain, landowner and amateur botanist. He spotted this unusual hybrid growing wild on his brother-in-law’s estate in Scotland, and took some seedlings to his home at Haggerston Castle in Northumberland, a mile or so from the causeway that conveys travellers across the sea to Holy Island.
Leyland was a rather splendid man, who devoted his home life to building a plethora of weird and wonderful buildings at the Castle (now a holiday camp), including an astronomical observatory built into a water tower, and a walled Italian garden. It is a shame that the folly that he is best remembered for is a monstrous tree, rather than the Greek goddesses and pergolas of the walled garden.
There’s a BBC article on the species, with a few pictures here:
 Leylandii are also popular in Australia, where they are known as ‘Leyton Green’ or ‘spite trees’ – Problem Hedges Australia is the campaign group for those affected.