those dam laylandii

Can't you just cut them back and make a hedge from them? If you keep them clipped they make a good one. If you really want to kill them, what are you going to do when you have a row of ugly dead trees?

they are a hedge at the moment,i want to get rid of them and try to grow a small amount of vegitables in the space,i dont mind a row of dead trees for a year or so but i want to kill the roots and tops to ease removel

In that case you need a product with 'Glyphosate' in it. Read the label and instructions carefully, as it will kill anything it touches. Obviously, if you are spraying, choose a completely still day! Better not to spray if possible, if you can get a pour-on-the-roots one. my friend has lost everything in her garden because her neighbour sprayed weedkiller and it drifted into her garden. OOOOPS!

if you cut off every branch and every bit of green they are unlikely to reshoot what you are left with are the trunks that will form a good basis for climbing plants if you either wire or add trellis. I have seen this done and it does look good! Honest

I wanted to kill some Nandino which also can't be dug up and the garden center I use regularly and trust told me to get a brush killer for pants other than Poison ivy. It will only taint the ground for about 2 months and then you can start replanting. Once the trees are dead, you can grind out the stumps and discard. (Don't use in your compost pile as it may poison all of it. I would just send it to the dump.)

f you do it now and let the ground sit fallow till next spring all traces of the Brush killer shoud be well gone.

Hope this helps
Miss Flitterbug