Carnivorous Plants/Bog Garden


QUESTION: Hi, I wonder if I can pick your brains a little please. I'm in the UK and I am putting a 2m x 2m x 962mm high raised pond in my garden. At one end the same width and height but 1 metre in depth I am going to build a bog garden. The top of which will be at the same height as the pond (but separated). I will grow the usual sarras', sundews and VFT's. The temperature can go down sometimes like last winter to -20C so I suspect even though its quite large I need to treat it as a container garden ?

The one thing I can't get a definitive answer is the best soil depth that will suit the plants. I will put a liner within the pond but with a 2" fine mesh plastic netting at the top to allow top drainage.

I'm also planning on the surface been covered in live sphagnum moss.

Any advice on this would be gratefully appreciated.

I would just also like to say thanks, I have learned more in a couple of weeks with your blogs, info and YouTube videos than I have in the last year or so. I'm also eagerly awaiting the videos c/o

Regards from the UK :-)

ANSWER: Did you really mean that your temperatures go down to minus twenty Celcius?  (-20C?)  This seems very unlikely for UK.  If you meant minus two degrees Celcius (-2C), then that seems more appropriate. (Avoid using 0 or O for the degree symbol.  This can cause a lot of confusion.  On my Mac, I press shift-command-8.)

Your weather is relatively mild compared to what cold hardy carnivorous plants experience in the United States.  You don't have to worry about frost damage to your plants.  If you were in the United States, you would be USDA zone 9.  

I'm a bit uncertain about your description of your setup.  Were you thinking about not filling one end of the pond with a peat mixture going all the way to the bottom?  If not, what were you planning to use to elevate the soil?  I'm also not sure what you mean by a 2-inch fine mesh plastic netting at the top.  

In any case, your question was primarily about soil depth.  Provide a depth of at least 300mm.  This will give your Sarracenia and flytraps lots of space to grow their roots in the years to come.

Good growing!
Jacob Farin

---------- FOLLOW-UP ----------

QUESTION: Hello Jacob,

many thanks for the reply and sorry for been a bit vague.

Yes, last winter we had 10 days where it didn't get above minus fifteen C during the day and peaked at minus twenty C a couple of nights but this is as you say not the norm. Minus eight is usually as far as we go down during winter.

The bog garden will be a completely separate entity so will be enclosed water reservoir. I was going to put around the top down to a depth of 25mm from the surface a plastic mesh to allow water out and stop water-logging but retain the growing media or should I just drill holes in the liner ? We get alot of rain in the UK !

The actual bog garden will have a floor in it so that I can set it the depth you've recommended. It will actually house the pond ancillary equipment under it.

I'll try and post some pics on FB when I get on with it.

Once again many many thanks

ANSWER: I didn't realize UK can get that cold.  That would make your region USDA zone 7.  You will need to offer some sort of protection during that type of cold spell.  In any case, because of the volume of water, you could almost think of your bog garden as an in-ground garden.  The water will insulate the soil from extreme sudden changes.  

Keep in mind that regardless of where you put your drainage holes, the water level beneath the top soil will always be at the same water level as the pond.  You will need to find a way to elevate sufficient top soil above the pond water level.  Or you will need to lower the water level well below rim level of your liner.  

My recommendation of soil depth of 300mm was exclusive of water level.  Regardless of the water level, you still want at least 300mm of soil depth to allow proper growth of roots in the years to come.  However, you should have at least 150mm of soil above the water level.  

---------- FOLLOW-UP ----------

QUESTION: Hello again Jacob, , I've confused myself now lol.
The bog garden will be completely separate from the pond water so I can set the depth to what I require. Just to clarify,the soil depth should be 300mm but the water level should only be 150mm within the soil ?

Sorry for so many questions about this and thanks for the advice.

Kind regards,


1) The total soil depth should be a minimum of 300mm, from top soil to bottom
2) The portion above the water line should be a minimum of 150mm.
3) The portion beneath the water line can be whatever you want as long as the first two requirements are met.

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