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Best compost for water retention - any recommendations?

Some of my south facing border has some kind of a concrete block underneath it. That makes it quite shallow (at some areas only 6in) and very free draining as the concrete block is kind of tilting. 
The plants were obviously struggling there, so I have now removed the soil from this spot and would like to replace it with some really water retaining material. 
Would anybody have any recommendations for me please: what material is best (manure, compost etc), any good brand? 
I‘d rather not use water retaining gel bits - I find them a bit yucky when they are wet. 
Thank you 😊 
Surrey

Posts

  • DovefromaboveDovefromabove Central Norfolk UKPosts: 82,269
    I would use a mixture of sieved topsoil and well-rotted farmyard manure ... around two thirds topsoil to one third manure ... I agree with you I really dislike the gel and Ive yet  to be convinced that it’s not going to be found to have some sort of harmful effect before too long. 

    However only 6” of soil is always going to be in danger of drying out quickly. 

    I think you need to be strategic when choosing the types of plants for those areas, and mulch, mulch and mulch again 😉 

    Good luck 😊 
    “I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh







  • I would use a mixture of sieved topsoil and well-rotted farmyard manure ... around two thirds topsoil to one third manure ... I agree with you I really dislike the gel and Ive yet  to be convinced that it’s not going to be found to have some sort of harmful effect before too long. 

    However only 6” of soil is always going to be in danger of drying out quickly. 

    I think you need to be strategic when choosing the types of plants for those areas, and mulch, mulch and mulch again 😉 

    Good luck 😊 
    Thank you my lovely Dove. 
    I’m heading to the GC tomorrow to get some farmyard manure. 
    In the shallow area I was thinking of plantings lavender - as far as I know they are quite shallow rooted and are drought tolerant. Or so I hope 🤞 
    Would Rudbeckias be comfortable in a shallow bed? More than 6in but still quite shallow? I have a few in pots waiting for permanent position...
    Surrey
  • NollieNollie Girona, Catalunya, Northen Spain.Posts: 6,551
    I have a part of a bed that is no more than 6” deep (impenetrable rock underneath). I have euphorbia and shrubby agastache that seems to cope. I found that if I plant small plants no bigger than 9cm pots the roots seem to find their own space, but I tried a larger pot and it just stayed in it’s pot shape and sulked. Whether they will survive long-term, I don’t know. Lavender won’t like the manure, you would need a really gritty, free-draining soil for that. 
  • FoxiesFoxies Posts: 60
    edited August 2019
    If it's free draining and very shallow, why not try some alpines ... I've just discovered these and I'm delighted at how they've held up in the recent very dry hot weather. I made tufa troughs on top of a breeze block wall so only in a space 4" wide by 5-6" deep. The delospermas have taken off a treat!
  • Thank you @Nollie and @Foxies , going to GC again today to see what I can get. 
    Another idea would be to plant bearded irises there, at least at the back. They are quite shallow rooted and the rhizomes even need to stay visible? Or maybe not? 
    I have a few irises that probably would need dividing and now is the perfect time too. 
    Would anybody know how long are they roots please? I never replanted them before as the came with the house. 
    Surrey
  • NollieNollie Girona, Catalunya, Northen Spain.Posts: 6,551
    Yes bearded irises, need to have the rhizomes exposed, don’t know about the roots, I too inherited some, in a big stone pot. They badly need dividing so will find out soon! I am going to try and transplant some of the irises to that bed, plus plant some smaller bulbs in between the euphorbia -coralloides and polychroma - like species tulips and allium moly.
  • Joy*Joy* Posts: 571
    Bearded irises have a fair amount of roots but mine seem quite happy to be moved. I brought a single rhizome of several colours from my old house. They had to manage in a pot over winter, then they spent the summer in the garden and produced one flower spike each, then just before Christmas were moved again and flowered profusely this summer.  I'm about to do some relocation again as they have already outgrown their spot. I'm still digging up roots from their first home! Providing that they have some roots and the rhizome is above ground they should be fine. Make sure that they get baked to ensure flowering. 
  • FoxiesFoxies Posts: 60
    edited August 2019
    There's a thought Big Blue Sky ... I have irises which I inherited in a gravel bed laid over anti-weed stuff so only in the top of the gravel which is about 5ins deep - they flower profusely (though what an excellent excuse for a GC visit  ;) )
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