Hello Flynn,
Conifers as large as yours are notoriously difficult to move and the
survival rate is low. Try and find out what it is first, and if you really
want to keep it or move it.
You will need to dig the receiving planting hole first .. it will need to
be wide and deep. Then dig out your tree with as large a rootball as
possible. You will need at least one strong friend to help you (and another
to make the tea). Wrap the rootball in sacking or plastic sheeting to move
it to the new hole. Add bonemeal during planting (unless you have
dogs/foxes!). Drench the soil, and even spray the foliage .. then drench
the soil .. be prepared to keep this up till the tree 'takes'. It would
also be advisable to stake the tree well and provide a windbreak, which will
also protect it against frost.
If you are doing this for a leylandii .. yes, you are mad! :~)
If it's what you want, I hope it works.
Spider
Flynn wrote in message
...
Hi

I'm thinking of moving a conifer (I think its a leylandi) from its present
position to one a few yards away (there's a couple of good reasons for
this); it's about 16ft high, 6ft broad.

Do those sizes give an indication of the root spread? How difficult is it
to
do this? What should I bear in mind? Am I mad?

Any advice gratefully received

Flynn