Most of us have a stash of empty plastic water bottles building up at home, and a balcony garden that could always use a few more pots. Instead of sending those bottles straight to the recycling bin, you can put them to work. With a little cutting, poking and tying, one humble bottle can turn into a planter, a watering system or even a mini greenhouse. They’re light, free and perfectly sized for small balconies, which makes them a great fit for apartment gardeners. Here are five easy ideas to try.