building raisedbed/wall as in Wisley Aug 3, 2007 log

[Robert Pavlis]

I would like to build a raised bed as pictured in the Wisley log Aug 3 2007.

What material is put in the middle lower section? Has anyone done this in zone 5 where frost heaving is a problem? What are the dimenstion of the one in the pics?

[mark smyth]

do you mean what planting mix?

[Robert Pavlis]

Not so much the planting mix, but what is below the planting mix - or does it go right to ground? Do you put stones at the bottom for better drainage?

Is there anything in the lower section to hold the walls in place?

[Anthony Darby]

Broken bricks is a good medium to fill the bottom half.

[David Nicholson]

Or small to medium sized stones, ideally covered with turf so that the good drainage available doesn't get clogged up with soil.

[Andrew]

madtripper/rpavlis,

Have you seen this topic ?

http://www.srgc.org.uk/smf/index.php?topic=768.0

PS Would you like to add you name and place to your signature so we can address you nicely ?

[Maggi Young]

And this, Wisley Log 3 2007 : http://www.srgc.org.uk/wisley/2007/300807/log.html

[David Shaw]

The bottom of such a raised bed is a usefull place for getting rid of waste stone etc. BUT, make sure that the stones are well mixed with soil to avoid void spaces. If there are voids the soil from above will filter down to fill them and you could end up with big potholes on the surface. I know, I have made this mistake and had to reconstruct the bed.

You also need continuity between the surface of the bed and the soil beneath to allow water to wick up to the plants and prevent the compost drying out too quickly.

[Paul Cumbleton]

Hi Robert,
I only just saw this topic - I look at the specific Wisley one regularly and the Pleione one but find it hard to keep up with the whole forum!

The beds you pictured are about 6 metres long, 2 metres wide and 60 cm deep - although we are about to shorten them a bit so they match up with the lines of the new display house more accurately. These beds have not been replenished since I came to Wisley (and are long overdue!!) so I don't know what was used to fill them in the lower parts. If you can afford it, use proper compost all the way down. This is the preferable option because it is always best to avoid putting different "layers" of things as this can mess up the drainage (due to effects that occur at the boundaries); if you do decide to put rubble etc at the bottom then the advice already given by others on this page about avoiding air pockets is very sound.

We will be re-soiling and re-planting the Wisley beds sometime in March. It will be intersting to see what we find in the depths!

Paul