Preventing spread of blackberries

Some years ago I planted 2 small blackberry shoots along the rear fence of my yard. While I love the blackberries I get, I now have 50+ plants and they are migrating forward into my yard. Last year I dug and removed the plants that had come too far forward from the fence. My goal is to do something permanent to keep the grass out of the blackberry area and the blackberries out of the grass.
My idea is to dig a narrow trench (30 to 40 feet long) parallel to and a few feet away from the fence (basically an arms length away) and bury something like alumninum that is sold in rolls of various widths to prevent the roots from migrating across that border, then maybe later putting down rock inside the border.
My questions:
1) How deep does material need to go? I am guessing 6 to 8 inches or will the roots eventually go deeper and come under? I would like this solution to last 20 years or more.
2) If I put some rock down where the blackberries are will I kill them off accidentally? I want to keep the blackberries, just contain them and have an area that still looks reasonably attractive in the winter when the canes have been pruned back to the ground. I am guessing a thin layer of small landscape rock might be okay or should I go with a mulch?
3) If the alumnium is a bad idea, why, and what would you suggest instead?
Thanks in advance for any and all help or humor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My Triple Crown Blackberries propagate by bending over and sinking their tips into the soil to form a new plant. If yours are like that, can't you simply discourage that kind of thing?
Sherwin D?
1_Patriotic_Guy wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I DON'T KNOW WHAT TO SUGGEST EXCEPT A WEED WHIP WITH A METAL BRUSH BLADE, SOME STEEL TOED SHOES, AND FACE & EYE PROTECTION. IT WON'T TAKE LONG IF YOU HAVE THE CORRECT EQUIPMENT AS THE STALKS DON'T GET BIG ENOUGH TO BE A PROBLEM FOR A GOOD WEED WHIP. I HAVE A STILL COMMERCIAL MODEL AND IT WOULD CUT THROUGH THEM LIKE BUTTER. BETTER START A NEW COMPOST PILE OUTSIDE THE FENCE FOR THE VINES AS THEY WOULD NOT BE MUCH FUN TO HAND HANDLE. HOPE THIS HELPS. PS - THINK THE METAL BARRIER WOULD NOT HELP AND SINCE THE BLACKBERRY SPREADS FROM THE TIPS AND ROOTS, THE TIPS WOULD JUST JUMP YOUR METAL BARRIER. REGARDS - JIM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.