[Peterpc]

My allotment suffers quite badly from Mares Tail. Could I grow raspberries in a trench lined with Mypex and filled with clean soil to discourage the Mares Tail? What size trench would I need?

[Mr Dog]

It won't take long for the Mares Tail to be through the mypex so I'd just plant the rasps (they have pretty shallow roots and won't really be affected by the MT which has v deep roots) - their shadow will likely help keep the MT down amongst them.

[Yorkie]

I tend to agree.  And raspberries like to send runners out for the next year's canes, so a trench can end up being quite constricting if you're not careful.

[Lulu]

My allotment is full of mares tail, and I just weed it from around the raspberries.  My raspberries are in slightly raised bed to try to keep them from wandering off.  Works well for me- there is an abundance of raspberries so far this year.