Raised bed under neighbour's conifer?

starrysky

Hi all,

I have a North-East facing garden so the back of the garden gets the most sun and I am keen to make the most of this by heavy planting at the back!

However, having shifted the gravel left by previous owners next to the fence, I realise that there is a thick mass of conifer roots, from the conifer on the other side of the fence. This is not a bad looking conifer, and does not block out any light due to the orientation of the garden. I am currently digging over the patch and clearing some roots (hoping I don't kill the tree as it is providing lots of privacy so that our house is not overlooked!), but the part by the fence will not grow much without some form of raised bed I am sure.

My question is, should I put in some sort of membrane at the bottom of the raised bed to prevent the roots invading and taking nutrients/ water from the bed? I read that you should avoid doing this if growing shrubs in the raised bed, which I did want to do... any ideas?

starrysky

Thanks in advance!

Obelixx

You are right that the only way for you to grow anything over those roots is by raising the soil level.  However, most trees don't take well to having their roots or the base of the trunk buried.  If you can reinforce the fence by building a solid back from railway sleepers or scaffolding boards and then make a raised bed a foot or two deep in front of the fence it should be OK.

The depth depends on what you plan to grow.   Shrubs, roses, clematis etc like good deep root runs.  Herbaceous borders of mixed perennials and annuals need less soil.   

starrysky

Thanks Obelixx! I was planning to use railway sleepers. I would quite like a mix of shrubs and perennials... or do you think it is a better bed to get shallower rooting plants only and put some form of weed membrane at the bottom of the bed?

Obelixx

A weed membrane is agood idea just in case the conifer decides to explore upwards but the eventual depth really does depend on what you want to grow.   As it is raised, it will be a lot like a huge pot or planter and need watering in dry spells and shrubs and roses need, as I said, greater depth to be able to access nutrients and water and keep their roots cool.

Lizzie27

If you do want to use a weed membrane against the conifer roots, you really need to pay a lot for a good quality, really trough membrane - something like Terram, if you can get it, which is over £100 + for a big roll.  We found out the hard way that most weed membranes are no good against tree roots. You may be able to get hold of a bit by advertising on Freecycle or Gumtree.

starrysky

A good tip Lizzie! I will have a look. I guess I would rather fork out now than have to dig it all up in a year or two when I realise the roots have overtaken it. Thanks Obelixx. I am getting two water butts soon hopefully to help with the watering!

starrysky

There is a concrete path that runs to the back fence, in the middle of my garden (the area under the conifer is on the left). Having dug on the right side of the path, as of yet I can't see any roots. I was going to take the path out, but now I wonder whether this is also serving as a bit of a root block.. so maybe I should leave it in!

Lizzie27

That might be the easiest option, although a concrete path in the middle might limit your design options a bit. We left our concrete path in because it was quite long and led to a shed at the top of our sloping garden, but fortunately it was placed off centre near to the right hand hedge. I did widen it for practical use by using left over sandstone bits on one side infilled with pea gravel which looks a bit better. 

Obelixx

You'll only find out if you dig down and have a look.   A concrete path up the middle is not an ideal design feature.