Waterlogged in London - too much?

Discussion in 'Water Gardening' started by Rexluna, Mar 29, 2017.

  1. Rexluna

    Rexluna Apprentice Gardener

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    Hi, so I have a splendid grand project that I am embarking upon, probably way too big for a first time gardener like myself, but fail fast they say!

    I live in central London, and am lucky enough to have a 5m x 8m garden that catches the afternoon sun. I already put in a wonderful pond a couple of years ago, and now I want to expand to bigger and bolder.

    I want to turn fully half the garden into 2.5m of pond, next to 1.5m of bog garden.

    My intention is to:
    - Dig out both pond and bog area;
    - Put down the liner (with a high ridge between);
    - Refill the bog area with soil, and have it slope up from the pond to about 30cm high;
    - Fill both areas with water;
    - Have a fountain, fed from the pond, to be constantly leaking into the top of the bog garden area;
    - Plant up the greenery, turn on the fountain in Spring, and leave the garden to itself - the ultimate hassle free wilderness...
    (I will then put in a pier from the other part of the garden, over the bog, as a jetty into the "lake")

    My problem, as I see it, is that I will be creating an artificial water table that will be between 0 and 30 cm below the soil, and while I want a bog garden for Gunnera, tree ferns and other grand wetland plants, many seem to prefer damp to waterlogged soil.

    My questions then, are, will the 30cm bank provide sufficient drainage for this bog garden? And what can I grow in the more waterlogged area right by the pond? Or should I pierce the liner in the bog garden area? (which might have problems of its own)

    And what other problems am I setting myself up for...?

    Many thanks!
     
  2. Clare G

    Clare G Super Gardener

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    Hi! I'm another London gardener. Replying because I too have a pond, which looks after itself pretty effectively, though it is unambitious in scale compared to yours....

    Some potential issues which struck me reading your post:

    Can you utilise rainwater (better for the plants, and your water bill)? My pond is fed from the waterbutt's overflow.

    How will the fountain be fed? By recycling water round the system?

    How will excess water (inevitable sooner or later when we get heavy rain) drain away?

    Could that process adversely affect your foundations, or your neighbours?

    Are there any utilities (drains, power cables) in the way? If so, are you prepared to move them?

    What will you do with all the soil you dig out?


    All things to consider....

    On a more positive note, I'd suggest a trip to the Woodland Gardens in Bushy Park or the Isabella Plantation in Richmond Park for plant inspiration - both have lots of lovely waterside/bog garden planting and should be looking their best over the next couple of months.
     
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    • Rexluna

      Rexluna Apprentice Gardener

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      Hi, thanks for this. Yes, all isues I've been thinking about -
      * to a degree I can use rainwater, but mostly I'll have to rely on the pond plants I alreay have to clean the new water
      * the fountain will draw water from the pond, and the system will be connected so that the water, in theory, will either evaporate from the plants or eventually flow back to the pond
      * I presume as it does now - into the soil. Even if the pond were full and could take no more, the rain would already be soaking my neighbours' gardens, so the pond run off would be no greater than if it were a layer of concrete, possibly less if the soil is not entirely waterlogged to start with
      * I'm being careful to dig away from any walls, and even then only shallow within a metre of the wall
      * no utilities
      * I have the rest of the garden to put it in, and overall it might even allow me to raise my pond slightly

      Great questions though, I am glad that I have covered them it encourages me that I have not been too remiss.

      Questions remain though, about the drainage of the bog garden.

      1) Will the 30 cm drop to the pond / water table be sufficient to drain the soil for plants like Gunnera and other bog dwellers?

      2) What will grow in the more waterlogged area?

      and
      3) Should I pierce the liner of the bog garden?

      Thanks
       
    • shiney

      shiney President, Grumpy Old Men's Club Staff Member

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      • Clare G

        Clare G Super Gardener

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        Sounds like you've got some expert advisors coming along, Rexluna:)! I'm sure they'll be able to answer your specific questions better than I can. Marginals that do well for me here are water hawthorn and papyrus nana, placed on a shallow shelf in the pond itself, and the fern osmundus regalis (rather spectacular, avoid too much direct sunlight or it will scorch) and gardeners' garters (a stripy grass), in the 'boggy' area (actually a gravel-filled tanked area beside the pond). The papyrus is meant to be tender but has survived a couple of winters now - we are lucky in London with our warmer microclimate, it is certainly worth taking a punt on some tender things.

        If I had more space I'd certainly be considering things like water flags and gunnera - do go if you can to see the Isabella Plantation/ Woodland Gardens to see these and many other fine plants (Can't post a link as I am a new member but google 'Royal Parks London). Both gardens use a diverted river to create lakes and streams in a woodland setting, with lots of good marginal planting. There are also many camellias (in flower now) and rhododendrons and azaleas (in flower in a month or so), often planted so as to reflect spectacularly in the water.
         
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        • kindredspirit

          kindredspirit Gardening around a big Puddle. :)

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          Answer to A. I would imagine that slope would be sufficient because marginal plants survive in poorly drained soil.



          Answer to B. Thalia Dealbata – ideal for London. American Skunk Cabbage. Lobelia Queen Victoria. Arum Lily. Primulas. Meadowsweet. Iris. "Some" Canna Lilies. Bulrush. Weeping Sedge. Uncina Rubra. Osmumda Ferns. Marsh Marigold. Loddon Lily. Pond Forget-me-not. Ligularia (particularly the one with the purple leaves.) Yellow Carex. Ornamental Salix. Those are just off the top of my head.



          Answer to C. I don't think so. (You can always do it after, if you wish.)
           
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          • ARMANDII

            ARMANDII Low Flying Administrator Staff Member

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            Hi Rex, I dug my pond out which is approximately 12' X 22' and around 3' in depth, with ledges around 3 sides down about 9" and about 10" wide to accommodate marginal plant crates.

            There is an alternative method you might want to consider. I took a tip from the late Great Geoff Hamilton when he built a wildlife pond on one of his programs and which I incorporated when building my pond. The easy method to make a Bog Garden that you
            don't have to worry about drying out is how I did it and that was to use old bricks to build a "dry brick", e.g: no mortar, wall and one/two brick above the estimated water level instead of the high ridge so the Bog Garden is integeral in the pond Fill in the space with ordinary garden soil [not aquatic compost as sometimes recommended]. Then when you fill the pond with water the water will seep through the gaps in the dry brick wall and keep the Bog Garden constantly moist as it's being fed by the pond. I did that when I dug out the pond in 93' and never had a problem. Another advantage to that method is that the Bog Garden plants help extract excess nutrients out of the water to help stop algae etc, and keeping your water clear. I built the dry brick wall into the pond 4' from the bank and the entire 22' length of the pond and it's very easy to do. For me it's been a great success as I don't use filters or pumps to filter the water and, along with an over planting of marginal and surface plants plants, it has kept my water crystal clear just using the balance of Nature. You can see how clear the water is just by using natural methods
            [​IMG]
            I
            [​IMG]

            Around the banks and in the Bog Garden I use Hostas
            [​IMG]
            Ferns,Yellow Flag, Bowles Golden Grass, Marsh Marigold,
            [​IMG]
            A Skunk Cabbage which in in a small crate in on the marginal shelf next to two clay vases where the only pump I use to stream water out of one of them just to oxygenate the water during hot weather.
            [​IMG]
            [​IMG]

            You can see part of the "dry brick" wall on the right with the Red Buddha sitting on top of it.
            [​IMG]

            So in the Bog Garden I use Quamash, Dicentra, Ferns of different varieties, Astibles, Iris, Primula, etc and they all seem happy. My pond is purely a Wildlife pond which has climbing roses on one bank, Ferns and Hostas on another, the Bog Garden on another with a 6'-8' Jasmine and Clematis hedge to isolate it from the rest of the garden with a bench.......[​IMG]
            to sit on.:snorky:
             
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            • shiney

              shiney President, Grumpy Old Men's Club Staff Member

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              I said you'd get good advice from them :blue thumb: :snork:

              @Rexluna and @Clare G as you're both in London you're not too far from me. Why don't you both come along to my charity Open Day where you will have a great time and will be able to meet some of our members. They come from far and wide :dbgrtmb: and you would have a chance to chat to ARMANDII about his pond (he'll be coming from Cheshire).

              Special Invite To Forum Members - 2017
               
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              • Clare G

                Clare G Super Gardener

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                That's a lovely idea shiney - not sure I could manage it on public transport though (as I dont have a car).

                ARMANDII your pond is beautiful and that frog looks to be in seventh heaven!
                 
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                • shiney

                  shiney President, Grumpy Old Men's Club Staff Member

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                  @Clare G No problem as we're only 35mins on the rail line from Liverpool St. One of us would pick you up from the station (usually ARMANDII or Zigs, he comes up from Dorset, will do the pick up as we're less than two miles from the station which is a three minute drive away). All part of the GC service :thumbsup:
                   
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                  • Clare G

                    Clare G Super Gardener

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                    @shiney what a nice offer! I will bear it in mind, I'm not sure if I'll be free then but would love to come if I can!
                     
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                    • ARMANDII

                      ARMANDII Low Flying Administrator Staff Member

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                      Thanks Clare,:love30:The Frogs are quite happy in the Wildlife pond and you can hear them in the early morning and evening croaking like two stroke motors.

                      Well, it would be nice if you could manage it and, as Shiney says, we would be able to pick you up from the local Station, but like everyone you have other pressures and priorities in Life that can stop you coming:dunno:.:snorky: It really is a great day and everyone has a lot of fun so if you can't make it this year then maybe next year:dunno::snorky:
                       
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                      • Rexluna

                        Rexluna Apprentice Gardener

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                        Thank you for all your replies - for some reason my email didn't notify me, so I have only just seen them. And thank you for the invitation, that sounds really lovely, I will see if it is possible, very kind indeed.

                        What fun a waterlogged, wet flower and wildlife haven!
                         
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