Concrete Planters - liners?
We live in a end of terrace on a hill and have a courtyard which is on quite a slope. We are in the process of making it level! So concrete is already involved Along 2 of the walls we are using breeze blocks (which will be tiled) to create seats/storage but want to alternate with planters..so, I have a concrete shell for plants, which I read isn't such a great idea..we will drill down through the old patio to allow for drainage but should I line the planters with something? I obviously can't just fill them up with compost...I'm new to this kind of gardening so any help would be great.
l've attached a photo of my building site incase I'm not making much sense, (the outside all of my planters is going to be 425 high so almost another block). No plans for veggies just grasses, foliage and a few annuals.