Would doing this kill leylandii cypress?

IronSquirrel

One idea I've come up with for a gravel garden I'm working on would involve digging a deep, narrow trench to be filled with gravel, and it runs parallel with a line of tall, slim leylandii.
At the narrowest end, I'd be cutting into roots at about 2 meters from the tree, and about 2.5/3 meters at the furthest.

Would this kill the trees, which are all taller than my house?

Fairygirl

Unlikely 
Are you trying to get rid of them? Cutting back into the old wood will see them off.

Getting them reduced in height to around four or five feet, and hacked right back to the trunks will enable them be removed completely, using the stumps as levers, or just cutting back to the ground and leaving the stumps would allow gravel to be used up to the bases. 

IronSquirrel

Can't remove them, way out of budget. Keeping them, just don't want to cut of the roots and have them fall onto the garden. 

IronSquirrel

I think the trees are themselves at least 25 / 30ft tall.

The internet won’t give me a direct answer so I’ve taken the least BS-sounding answers to the root question, 

the Xs are the trees.
So from this, the roots are either going to be stretching out about
3 meters (inside the Green circle)
5 meters (inside the orange circle)
Or  above (no point circling because it’s above my pay grade to deal with that shit)

Also, the original intention of my client is to have the garden above the blue line bordered with some new shrubs. Will they even cope, given the conifers greedy roots ?

KT53

Cutting the major roots on one side of the tree probably won't kill it but it's very likely to destabilise it.  Strong wind hitting the side with the cut roots may well cause the tree to fall in the opposite direction.

Lyn

I had a row of leylandii which we removed,   The roots weren’t out to 2 mts,  I made a 2mt flower border so I would say go ahead,  if you’re  worried , dig down 2 mts from one tree and see what you have, 

seacrows

We removed a row of leylandii, not quite that high, maybe 20ft. The majority of the root system was within a metre radius of the trunk. The soil left was absolutely useless, dry powder with no organic material, couldn't grow weeds in it. If you want to plant shrubs you're going to have to pick them carefully, really enrich their planting pocket and water them profusely for months until they establish.

Lyn

That’s was unfortunate @seacrows,   Our trees were 30 years old when we removed them,  all we did was use some chicken pellets and compost/mulch, this is the area planted up straight away.
we took them out winter 13/14.  This is May 14. Just planting up.


This is July 14.

Lyn

Similar here with this border.  I would say the OP can go ahead with their border and leave the trees.  It can be done.   I’m sure it won’t affect the roots at 2 mts.   You may have to get plants for shade depending on which way the border is facing.

from this 


March 2019


July 2019

seacrows

Lyn said:

That’s was unfortunate @seacrows,   Our trees were 30 years old when we removed them,  all we did was use some chicken pellets and compost/mulch, this is the area planted up straight away.
we took them out winter 13/14. 

I think it might be mostly due to the underlying soil type. These were planted in heavy clay and left to grow untouched for 25-30 years. Apparently clay with all nutrients and water removed and no mulch/compost for 20 years gives you powder! That's a lovely border though. Are the stumps still there, because I can't see them.