On Sunday, June 24, 2018 at 11:57:34 AM UTC-4, Electric Comet wrote:
looking for the favorite planter box liner


or maybe i will just make drain holes


pond liner seems too stiff but seems to be the right stuff

Just went thru this exercise. Built 9 planters, all dovetailed corners, from PT lumber, sealed inside and out with 2 coats of clear Cabot waterproofing. Put 1/4" galv hardware cloth in the bottom, covered by weed blocking fabric. Lined the planter with 6 mil poly letting it hang/drape over the top edge, with the bottom scored so as to direct water to the bottom where it can drain. Using Plastic J molding (think vinyl siding accessory) capped the planter top and trimmed off the excess poly. Exterior of planter/capping was coated with exterior solid stain. Plants are doing great, will not know till next spring if/how well the planters themselves hold up...