I've had good success over the years with one of my own "inventions". A 2L coke bottle with a 10-15cm rag comming out the side near the top. Sink the whole thing into the ground so the lid is just below soil level (place a small rock above the lid so you can find it easy and refill it) and the wick is diagonally down but not too long or it seems to drain the water faster- like a siphon! Then you can plant right above the wick! Only needs refilling every 2 months and its invisible (completely underground).No matter how good your potting mix is it cant beat the sweet soil of mother earth for productivity- just ask any farmer. use cotton/polyester mix as cotton rots too fast. This does work and I did think of it first.