Pretty cool, but, I suspect the jeans will not last many seasons outside. That's probably the biggest concern. So, how I'd make: Waterproof the fabric with a spray on repelent. Maybe even do the inside with silicone sealent. No silicone on outside, to avoid changing the texture / look of the fabric. Looks like the legs were stuffed with round objects, maybe stones. However, I'd use a heavy duty trash bag in each leg, filled with bark mulch. Since the cotton will deteriorate over time, stones will be heavy enough to split the fabric / seams over time, which is why I'd use mulch. Definitely want to avoid moisture being held inside the legs (speeding fabric rot) so using a trash bag should stop that. Since most plants will only root about 1' or less, a pot in the groin of the pants will be deep enoough for planting. Plastic, with no holes, to avoid water leaking into pants. Use the tops of the leg bags to fill and form a depression for a container. Place a second, smaller container inside the first, with space and a little drainage to help avoid drowining the plants. (But water carefully!) Attach the hem of the jeans to the rim of the first pot, preferably with some sort of waterproof adhesive to help seal, preventing rain from getting in. Maybe impregnate the inside of the hem with silicone, let dry, then adhere to pot rim with silicone. Use a dry top-dressing like spaninsh moss to hide the pot rims and jeans hem. The legs with mulch should act as good supports for the weight, but tie the belt loops to the railing to keep from falling over. If freestanding, I'd use wood poles, planted in the ground then running up through the legs, with the bags of mulch surrounding and filling up. Watch out for contact between the pants and the ground, which will bring water up into the fabric. All said, keeping the cotton's color and integrity may take some occasional maitenance. Post an Instructable if you make something. Love to see your finished project!