Raised beds for Blackberries.

[DannyK]

Just got some 150mm gravel boards.

One or two levels needed please?

The soil under the bed will be dug to one spit.

[flynch]

What's the like soil underneath? If it's free draining one should be fine, if it's heavy clay and gets waterlogged I'd dig in some sand and then build two levels on top of that.

[bario1]

Why do you want them in raised beds? Generally they sprawl about all over the place and tolerate any conditions you throw at them. Most people have them at the edges of their plots and tie the canes to fences/posts/hedges to keep them out of the way.

[DannyK]

My soil has a tendency to sump so I thought I'd give them optimum conditions.
I have some in the soil and they don't romp away like those that were in sandy soil of Worthing.

Even monbretia don't spread here; in Worthing we used to pull out loads.

I'll go with two then at least if the blackberries fail there's depth for something else.