Waterlogged in London - too much?

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!

 

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.

 

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

 

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.

 

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.)

 

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!

 

@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!

 

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!