I wouldn't plant directly in it but would line the inside with something - either thick plastic sheeting (like the kind that comes in rolls in various "mil" thickness) or some sort of PVC insert or even thick trashbags that can be placed inside and then filled with soil for the plants. The inserts can be easily hidden with mulch, etc. Be aware that aluminum is highly conductive of heat so you may want to consider that if the plans are to use it in full sun (meaning alot more watering).