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What medium should I use and how deep ?

hartk10hartk10 Posts: 18
edited October 2019 in Problem solving
I’ve just finished revamping my patio. I’ve put a double wall around it, using those interlocking blocks, with the intention of using it as a large planter. By my calculations it works out about .9 meter cubed (7.5 L .3 B, .4D) I appreciate the breath is quite narrow. I’m figuring that to fill the above with topsoil I’d need somewhere in the region of 1.3 Tonnes

The difficulty is the only supplier I know of in my area won’t deliver this quantity he really does big jobs.  It would seem, therefore that I’m down to buying compost in bags - quite expensive !  I have loads of stones rubble and bark chipping so I’m wondering how much of a growing medium do I really require, what depth should it be ?

While I haven’t decided yet what I’ll grow in the beds I can’t see me wanting any deep routed plants. Feel free to make plant suggestions, I live in Northern Ireland 


ps sorry I might usefully have added this to a previous post on 15 Oct, forgive me 🤗


  • ObelixxObelixx Posts: 29,857
    I think you may be trying to put the cart before the horses. 

    First select the plants and determine whether they want alkaline, neutral or acid conditions to grow well.  Not a good idea to mix them up. and make sure their needs are compatible with your tap water as plants in anrrow troughs and containers will need regular watering from you.  

    Then check their eventual size as this will give you a guide to root depth needed.  Look each one up on something like the RHS site to check its preferred growing conditions and hardiness

    Then you can start to calculate the type and quantity of soil needed.
    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • hartk10hartk10 Posts: 18
    Some very good points to think about.

    I do have lime soil so I appreciate that restricts what I can grow. According to our local water authority we have soft water.

  • ObelixxObelixx Posts: 29,857
    If you are buying in soil/planting medium, you can grow what you like and give it what it needs.

    However, unless you want spectacular colour and foliage which will require good growing conditions, I suggest you look at plants that like well-drained conditions and are drought tolerant so things like sedum, house leeks, small bulbs like iris reticulata that won't mind too much if you forget to water.  You're may have to think of it as a long thin hanging basket really.
    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • LoxleyLoxley Posts: 5,565
    "What depth should it be?" - well you have a 40cm high planter, so 40cm should be about right. If I was you, I would put in a 10cm layer of small stones / rubble in the bottom (since you have them) to help with drainage, then fill the rest with bagged topsoil (Wickes has been the cheapest I've found). You are limited in what you will be growing because it's so narrow, I'm assuming things like herbs and perennials would be the direction you'd be going in.
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