flower border with colourful plant combinations

artemisa artemisia ludoviciana silver queen valerie finnis pontica digitalis purpurea falbiflora geum lady stratheden knautia macedonica potentilla blazeaway aurea gold clogs megalantha recta warrenii william rollison salvia nemerosa ostfriesland sylvestris viola klose sisyrinchium striatum verbascum chaxii norfolk dawn vabascum cotswold mont blanc flower flowers summer colour color colourful yellow orange white blue red burgandy square impressive border plant combinations