Grown as a tree, the Leylandii is generally dismissed by naturalists, especially the more ecologically minded as it is neither a native, nor particularly accommodating to wildlife. However, a Leylandii hedge can be an entirely different matter.
Smaller birds that frequent our gardens appreciate the protection afforded by the dense foliage of the Leylandii and any such visitor will gladly use a Leylandii hedge for temporary shelter or even, as in the case of the Greenfinch, for nesting. Many insects, including Ladybirds, will happily hibernate in a Leylandii hedge.
So, while it may not be at the top of the biodiversity habitat list, a well-clipped Leylandii hedge, especially when leaf and other organic debris is allowed to settle at its base (popular with many insects and smaller, foraging mammals) will still make a contribution – and to maximise its appeal to wildlife, why not grow, say, a Wild Rose or Clematis, through it?
As we have said before, wildlife has never thanked a gardener for installing a fence.