[VegWill]

Hi all,

I've recently moved into my first house. One thing I was really looking forward to was having a garden.
Unfortunately upon inspection I've found the soil quality to be very very poor. I've dug a few test holes and found mostly rubble. The soil is very sandy, stoney and is a sickly grey colour.
At present there is nothing planted in the garden. There is only a patch of scruffy grass.

So, my first plan of attack is to build a nice high raised bed. This is to serve two purposes. Planned height of 700mm
1. Provide enough quality soil depth for plants to thrive.
2. To raised plants higher up to provide screening. Achieving more privacy in a very overlooked garden.

I plan to build them from reclaimed scaffold boards which I have already acquired.
Planned dimensions of roughly:
3900x700x700.
Then fill with purchased topsoil.

What advice would you give to my proposed idea?
Should I treat the wood first?
What topsoil should I buy? (I live in Sheffield)
Are there any disadvantages to having very tall raised beds?

I plan to grow a mixture of flowers shrubs and veg.

Any advice is much appreciated.

Thank you for your time.

[diospyros]

That's going to be a lorra lorra topsoil.  I'm not sure plants actually need 70cm of topsoil.  I'm not sure scaffold boards will hold the weight either, you'd be better with sleepers for something that tall.  I'd say halve the height?  I'm just sat at my desk which is 70cm tall and trying to visualise it - how are you planning on laying it out?  Also you say you want them tall for privacy because it is overlooked, is this by other houses i.e. upstairs windows, or people walking by? 

I don't think I'd move in somewhere and go straight at it with a grand plan, especially one which involves such hefty constructions.  You need to get a feel for your plot first, especially where the shade falls at different times of year and what microclimate you have.  Try planting something really tough with a bit of added topsoil and compost - heck, I've seen buddleia growing out of solid concrete!   Look at natural habitats which have very poor soil, like limestone pavements and sand dunes, for inspiration. Get some cheap, free, recycled pots and containers for a quick effect and you can move them round and experiment.  Try and see the assets of your plot as well as the drawbacks.

[VegWill]

Thanks for your reply.
I agree it is a little drastic. Perhaps the hight is a little on the extreme side. The privacy issue to to screen between my garden and the adjacent one.
My house is 1900 terrace with a very small back garden. All the fences are only about 1m high. So there is literally no privacy between my house and the next and the next and so on.  Hence the extra height.

Where I plan to put the raised bed is along the left hand boundary ( looking down the garden) where a typical boarder would be.
There was a concrete slabbed path which I removed and relocated to extend the patio.
The hardcore for the path is still there, quite deep and compacted.


My plot faces WNW.

Thank you

[Trillium]

There's little use to making the beds too high since your better soil in the beds will satisfy all plants in the beds. Mine are about 18" high and that seems to suit most things I'm growing. I did make the Boking 14 comfrey bed deeper as the roots are very large and that bed is 24" tall.

If you're using regular wood, yes, treat it first. When it's dry you could also line the inside walls with poly sheeting to further lengthen the wood life. I painted the outsides of all my boxes so they'd look nicer and last longer.

As for filling the beds, you don't need #1 topsoil, just something reasonably decent and you can add some rotted manure and coil or used grow bags into the mix. Like ground beds, the raised beds will need yearly feeding as well.

[diospyros]

Ah, that makes things easier to visualise.  So like my garden, your sunniest spot in the evening will be down the bottom in the right hand corner somewhere!  And I bet you put the patio next to the house!

Thinking about it in the night I was imagining a square box hemmed in by blocks of flats, and thinking a pergola would give you a sense of privacy, but in a long narrow garden you want to keep the boundaries narrow or you will lose what little width you have and it will feel like gardening in a corridor.  So maybe you could try trellis fences to give you some privacy without feeling boxed in.  For climbers, wild clematis grows on the Chilterns on chalk with very little soil.  If you grew one of the varieties that usually grow huge, maybe your lack of soil would bring it back into sensible proportions!  Actually you quite often see big climbers (Hydrangea, Virginia creeper?) grown up against a house with very little soil at their roots.  Look around at what grows near you. Also I was wondering if you could possibly get away with a fig.  Don't know how far north they are hardy but you have the heat island effect of the city, and they are traditionally grown with roots restricted to encourage fruiting.   Then you could have your raised beds shorter in stepped groups to give you a range of soil depths and make it more visually interesting.

Gardeners love  a challenge!

[snow white]

You will have to bear in mind that a raised bed drys out really quickly.  The one on my allotment needed watering every day in the summer.

[Goosegirl]

If you do buy any topsoil, don't just choose a place and ring up, select say 3 places then go and look at it first, as it can vary between suppliers and also their current supply at the time.

[polly nator]

I have done exactly the same and had raised beds put in about six years ago.

As others have said - yes, you will need an awful lot of topsoil and you need to compare the quality from several sources.  But you do have the advantage that starting from scratch you can add layers of others things such as rotted horse manure, leaf mould etc

Bear in mind, that the level will settle every year for quite a while and you will need to top up.

Mine are 42 cm height and I wish they were a bit more.   With a very deep raised bed you can plant small fruit trees which would make your garden more private. I have a plum, crab apple and cherry.  You can get them with dwarf root stock.

Leeks and carrots will do well in a deep bed and the carrot fly wont bother the latter. I even have some asparagus - I know it would do better in open ground but its not bad!

The wood on mine is treated. One useful tip (depending on what height you choose) is to add some horizontal board/timber  ledges on top that you can lean/sit on.

I would definitely recommend your idea - it will turn a sparse,, unproductive spot into a green and leafy and productive garden

[VegWill]

I get the sun on the back of house in the evening. But it disappears at about 18:30 behind the houses.

The garden isnt very long. So I doubt I'll ever be gardening in a corridor.


I was concerned about raised beds drying out. Is there anything I can do to help it retain water?


Regarding those big bulk bags of topsoil... how much will that give me? Enough or will I require more?

I've looked at this place near me.
http://topsoilsheffield.co.uk/

Thanks again for all replies

[NewSteve]

Hi Will,

It sounds like your bed is going to be almost north facing. Why not put it on the other side of the garden where it'll catch the afternoon sun?

Also, rather than concentrate on one raised bed, you could spread organic material over a slightly wider area and improve all your soil gradually. Of course, that won't give you the quick win of one great bed to plant in!

[BobE]

Thanks for your reply.
I agree it is a little drastic. Perhaps the hight is a little on the extreme side. The privacy issue to to screen between my garden and the adjacent one.
My house is 1900 terrace with a very small back garden. All the fences are only about 1m high. So there is literally no privacy between my house and the next and the next and so on.  Hence the extra height.

Could you fit 2m fence panels?.  Maybe your neighbours would like that as well and help you to do it.  Then the privacy issue would be separated from the raised beds.  Also a 2M panel could be trellised and planted with climbers.

[Trillium]

To help my raised beds stay moist, I give them a heavy bark chip mulch on top, and before I filled the boxes, I lined the sides with heavy polythene sheeting. This keeps the air out of the plank joints from evaporating as well as protecting the wood. You could also run the sheeting across the bottom of the bed and do a few puncture holes for drainage to help retain more moisture, especially if you have large trees around. Their roots seek out water everywhere and fast. 

[VegWill]

I don't really want to fit 2m fence panels. It'll block out a lot light to a small garden. Also it seems a little rude to move in and start barricading myself in.

I would place the bed on the other side of the garden. But I have already got some small raised beds and a polythene greenhouse set up.

I plan to build further raised beds there in the future.

[Yana]

To help my raised beds stay moist, I give them a heavy bark chip mulch on top, and before I filled the boxes, I lined the sides with heavy polythene sheeting. This keeps the air out of the plank joints from evaporating as well as protecting the wood. You could also run the sheeting across the bottom of the bed and do a few puncture holes for drainage to help retain more moisture, especially if you have large trees around. Their roots seek out water everywhere and fast.

I've built 4 raised planters (1.2m X 1.2m X 60cm high) and gradually filled them with compost, manure and the occasional  barrow load of topsoil over two years. They are made of decking boards, painted inside and out and lined with black damp proof membrane to protect the wood. Having said that I have filled them over two years, I mean that I thought I had and every year they settle and need topping up. I didn't put the membrane across the bottom because I though the planter would get water logged. I now wish I had. I'm building some more, different heights and sizes and will line the bottom of them this time. Thanks for the tip Trillium.