Step One Peace of mind is two layers of 2mm HDPE rhizome barrier in one long piece, forming the ‘escape proof’ planter. This is good insurance against buried objects piercing the plastic and it also means that the join inside of the planter will not be the weak link. Heavy duty tape is run over the inside flap of the rhizome barrier to firmly secure it to the sheet behind. Make sure that the sheets are neatly held against each other before fixing the tape. << Completed 'escape proof' planter