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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,  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.



  • FairygirlFairygirl Posts: 54,819

    You could line with plastic (also with plenty of drainage holes cut in it) which will prevent the concrete soaking up too much moisture. It can be an issue with any raised beds as they tend to drain more easily than the ground. The proximity of the wall can also mean that the planters would be drier. 

    You may need to think of a way of attaching the plastic though, as that might not be easy.

    Alternatively, there might be a paint you could apply to help waterproof them a bit. I'm sure someone will have a recommendation for that - I've used Thompson's water seal on brickwork previously when I had a bed at the end of a deck which was in contact with a house wall. 

    Compost alone will be fine for annuals, but you'll need something more substantial for long term planting. A soil based compost, ordinary topsoil, and/or well rotted manure would all be ideal depending on what you want to grow. image

    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • Thanks Fairygirl. 

    We can attach plastic easily enough - like pond liner? Do I need to line with gravel either inside or outside the liner to help with drainage? Really appreciate you sharing your knowledge. 


  • FairygirlFairygirl Posts: 54,819

    Hi Sally - any heavy duty plastic will do. Pond liner's expensive so no need to use that. Something similar to the weight of compost bag plastic is fine. I have a big roll of black polythene which I've had for a while - I expect if you ask Mr Google, there'll be plenty to choose from  image

    Hard to tell the weight of it, but mine looks like this - 


    I had no need to put any at the base as my beds are all built directly onto gravelly ground.

    I'm not sure you'd need gravel, but if you feel it would help, it would certainly do no harm. Probably a layer on top of the plastic is better - it will certainly help to prevent soil clogging the drainage holes. A larger size would be best for that.  I prefer to mix fine gravel or grit with the soil/compost to get good drainage, rather than having a layer on it's own at the bottom, but it comes down to preference, and what type of plants you're putting in. It's similar to how you would plant up a pot - something over the hole(s)  to prevent clogging. image

    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • hogweedhogweed Posts: 4,053

    I would Certainly put a few inches of 10-20mm gravel in the bottom For drainage. Even if you do drill through the old concrete the boxes will not drain as quickly as if they are on earth. Put as many drainage holes in as you can especially if you line the sides. 

    'Optimism is the faith that leads to achievement' - Helen Keller
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