best wood for large corner planter

[britishboy7]

im going to have a go a making a 3 or 4 tier, corner planter, with each lower tier being larger than the last (almost like a set of steps). Ideally want the bottom ‘bed/step’ to come out approx 6ft from the corner of the garden

What wood should I use? Was thinking pressure treated 6x2? Or is there a larger, thicker size available? (Don’t want to use sleepers as they’ll be too thick)

Any suggestions or pointers greatly received gents

 

[freddiemercurystwin]

I've always used decking for planters.