[header] How to make a rock garden in a trough [title] Pick out the material you would like your trough to be. [step] You can buy a stone, metal or wood trough from the garden store; these tend to be fairly expensive. You can also use an old butler's sink or metal tub from the reclamation yard. 
Remember that solid stone troughs will be very heavy, especially once full of soil and rocks. [substeps] Try to get a trough planter with drainage holes, or, if possible, drill drainage holes in whatever planter you are using.