Flower Bed Trench Against A Brick Wall

Hi there,

Like much of the population at the moment, I'm keen to get on with some gardening duties.

We have a relatively small and bare garden with just lawn (sloping down at an angle from the house). I'd like to dig a flower bed trench against a boundary wall, so that I can plant climbers up it etc. I've attached photos of the wall.

Some questions:

• I've read on other forums that growing flowers along a brick walll can be tricky, since the brick can dry out the moisture in the bed. Would I be able to mitigate this, by lining the trench with some lining?
• I imagine I wouldn't need to worry about moisture damage to the wall, as I assume it's been 'treated' before the grass and soil went down.
• What sort of depth should the trench be?
  

Thanks for any advice in advance

Cheers

James