I am trying to add a low (say 18"), narrow (12"?) and about 25ft long wall to separate my flagstone patio (pinkish) from the grass area. I shall try to upload a drawing and photo. But basically it's the house, connected to flagstone patio (10ft x 50ft), then grass. On the other side of the grass facing the patio/house is a raised flower bed by round rocks about the size of basketball.

The little separation wall will be used to put flower pots on to of it and occasional sitting too.

What method and material should I use that will mesh well with the pink flagstone, green grass and gray/brown rocks?

I am debating woodform/stucco vs woodform/flagstone vs same round rock as bed vs just redwood ....

I am open to all ideas.

Thanks for helping.