Posted: 22/02/2015 at 16:11
A few interesting bits to consider if thinking of growing these trees.
from the guardian 07th dec 2012
"Leylandii's success is especially impressive when you consider that it can't reproduce, which means that every plant we see today comes from cuttings and has been planted by humans. How did such a mundane tree become so popular? Because it's evergreen and vigorous. A leylandii will grow three feet every year, so in no time at all you'll have factor 50-style privacy, something our insular society finds irresistible. The trouble is, it won't stop: the tallest one is already 40 metres (130ft) and still growing.
Live with it…
So what do you do if you have them (there's usually more than one) in your garden or, worse, a neighbouring garden? Management is crucial: this is not a plant you can turn your back on, especially when it comes to the soil. While deciduous trees will enrich the soil with organic matter in the form of fallen leaves, leylandii will treat it like a student treats a bank account – it's all take, take, take. Before long your soil will have turned to dust. You'll need to compensate by heaping on leaf mould, garden compost or rotted manure in autumn and spring."
Leyllandii is listed by the rhs under potentially harmful plants as causing skin irritations so should not be used as a hedge near young children I know it makes me itch when trimming
I cannot find exact figures but leyllandii are considered a high water consumption tree. Trees depending on consumption can consume 250- 300 gallons of water a day.
Daily mail May 2007
Leylandii, a house buyer's No 1 hate
Last updated at 21:39 20 May 2007
To the gardeners who lavish time and money nurturing their plots, they are no doubt precious.
But to potential housebuyers they are the ultimate turn-off.
Leylandii and garden gnomes are among a range of outdoor features which, researchers found, can knock thousands off a house's value.
"The fast-growing firs, often planted to give privacy, topped the poll, with 71 per cent of 6,000 people questioned expressing hatred of them and citing their well-known ability to cause disputes with neighbours.
Ivy was second on 67 per cent, pampas grass third (55 per cent), conifer trees fourth (50 per cent) and wisteria fifth (49 per cent).
Gnomes are the least popular garden ornament among housebuyers, with 67 per cent putting them at the top of their hate list.
Water features and ponds were second on 59 per cent, pet cemeteries third (55 per cent), dilapidated greenhouses fourth (43 per cent) and extravagant Christmas decorations fifth (29 per cent).
The survey was conducted by www. uktvgardens.co.uk."
Peoples intentions are often to keep these hedges clipped, but unlike other hedges that will not go mad if you cannot get out to clip them due to ill health or other circumstances Leylandii will run away from you beyond restoration to a neat hedge very quickly. If your garden is like many only 20 or 30 foot wide and a long narrow strip you will use up all the nutrients in not only your soil but your neighbours in only a few years . Another tree that should be used with caution along side the leyllandii is the eucalyptus, fast growing with huge water consumption in a typical terrace garden the roots will shoot under the neighbours garden in no time sucking all the goodness from the soil, it is a few years behind the leylandii but the eucalyptus will I think be the next tree causing a similar controversy in small terrace homes and gardens.
If the original poster's trees are dying, given the above, she and her neighbours may of had a lucky escape.