How to make a Sub-Irrigated Planter. I'm not sure I would use a two liter plastic bottle though. Over time I would fear the plastic breaking down enough to poison the plant. Perhaps a wine bottle instead.
Self-watering planter. Cut top third off bottle. Drill small hole in cap. Pass string thru hole. Fill bottom of bottle about halfway with water. Place top upside-down in bottom and put plant in. String will wick up water.