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Will shallow soil prevent plants from growing well?

I fear the answer is yes but someone may be able to advise.

I have cleared an old deck area and have started digging the ground at the back of my house (north facing)

When I started to dig down, unfortunately I hit fairly hard ground about a foot down (30cm). This is made up of hard clay and stones and was really difficult to dig into with a fork. The beds will be around 3 meters long x 1 metre wide at its widest.

I have been planning this garden for a long while, with it having an exotic theme mixed with perennials suited to shade. Plants consist of the following:


Hot poker

Fatsia japonica
Canna plants
Bamboo nigra
Banana musa Basjoo
Tree fern

I’m worried now that these plants won’t grow to their full potential with the restriction of soil base as I really wanted these plants to get to a good height, but now they will likely be competing against each other.

Any advise on what I could do here? Will the plants suffer or stay small due to lack of depth?


  • gardenman91gardenman91 Posts: 429
    Hi oreilly

    Is it a large planting area in the middle of the decking? Would you be able to post a photo?
  • edhelkaedhelka Posts: 2,350
    Begonia, hosta, ferns, crocosmia and euphorbia will be fine. Dahlia, lily and hot poker probably too. But it is not enough for shrubs and larger plants.
    Fork really isn't a good tool for digging deep. If it is only clay and stones and nothing worse, it sounds like a job for a pickaxe.
  • LatimerLatimer Posts: 1,034
    edhelka said:
    Fork really isn't a good tool for digging deep. If it is only clay and stones and nothing worse, it sounds like a job for a pickaxe.
    Or a mattock, a tool i became familiar with digging out clay and stones myself!
    I’ve no idea what I’m doing. 
  • NollieNollie Posts: 7,324
    That does sound like a very long list of plants to squeeze into a 1x3m space, even if the soil was rich and deep, so I think you need a good edit of your list - maybe choose one or two maximum from your final list of larger plants. I would scrap the black bamboo, it is a bit of a spreader. Perhaps a fargesia type bamboo in a pot - large pots could be the way to go to increase density and create a lush, exotic theme. Depending on where you live, the Canna, Banana and Tree Fern will need winter protection, and if you choose lightweight pots that you can move, they can be put in a more sheltered environment for winter.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • GemmaJFGemmaJF Posts: 2,286
    Regardless of the depth, it sound like 'hard pan' which can give drainage issues, so ought to be broken up. 

    I have a tool that is a pick axe one side and a mattock on the other. That's the one for the job!
  • FairygirlFairygirl Posts: 53,959
    Not only do you have too many plants for a border that size, many of them won't thrive in a north facing site.
    Yes - clay pan. You'll need to loosen that completely, then do a wee bit of research re the types of plants which will suit.
    Dahlias, Cannas, Bananas all need rich soil for example [as well as winter protection] , while Crocosmia, Pokers and Euphorbias prefer quite poor soil.
    Some will grow in sun or shade [Euphorbias, Crocosmia] but many of those plants need a sunny site in order to grow well. 
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • ObelixxObelixx Posts: 29,645
    The main problem will be that that hard pan of clay and stones will impede drainage and your plants' roots will sit in a bog in wet weather and then rot and die.

    You can try and break it up with a pick axe so that drainage improves and deeper roots can eventually penetrate or you can build a raised bed which will give you greater soil depth and better drainage.   That will involve finding suitable material to build the raised beds plus decent topsoil to fill them.

    Then you need to research the eventual size and spread of each plant and calculate how many will fit in your small space and edit accordingly.

    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • Hi There,

    Thanks for all the great tips and the advice on the clay. I will be back out today to have a good look at it. I have a pick with a thinner mattock and so will try this.

    With regard to clay pan - do I need to remove this clay and replace with drainage, or can I just break this up to a certain depth?

    Perhaps I should have posted some photos and a plan to give you an idea of what I have in mind. See some progress photos below and ideas

    This photo from a couple of years ago.concrete slabs sitting on a old deck of this tiny space. raised beds to the left and sheds and the end to be removed

    Drew up some design ideas. We want to be able to follow the path to the end of the garden for a beer in the evening. Planting is not finalised and still researching and learning at this early stage

    fast forward a few years until I have the time to work on it, to remove the shed and slabs. Now to get a skip, and remove the raised bed wood and decking.

    Deck removed and about to set out the beds. Ground is level enough for new paving so hopefully don't need to add much more hardcore.

    Added in the area for beds in red with paving through the middle.

    Before I came across the clay issue, I had played around with a layout like above. Overall the site is very well sheltered from wind and frost and even though its north facing, it heats up and still gets a good amount of sunshine.

    I think the fatsia, tree fern, and trachycarpus will be happy with that amount of shade, while the bed on the right receives a good amount of sun in Spring/Summer/ Autumn. I will be protecting any of the tender plants over the winter. I have a good amount of these plants in pots already and have been able to see how they perform in the area, albeit in pots.

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