Last year I tried many new things and one was with containers of all sizes. The problem with lots of containers is that the water runs right through the soil with most containers that have holes in the bottom are ae using dry potting mix that does not hold water. i use this several times last year and it worked great! I don't always mention what I try because I do some crazy things but if they work! +++ I use alot of water bottles and save them for many uses. I cut the small 16 or 20 ounce bottle in half and can use both ends. In small containers I cut the bottle about 1/4 from the bottom and place it in the bottom of my container before I place the dirt in the contaier. The plastic water container sets in the middle of the plant container on the bottom only about 3 inches high depending on the size of the planter but only coming up about a third. from the heigth of the planter. Even 2 inches will work in most small planters! +++ A 6 inch pot I have a 2 inch water bottle on the bottom! When you water the plant water stays in the plastic bottle and the plant roots absorbe it over a longer period of time compared to the water that runs out! You can even run a straw to the plastic collector and add fertilizer directly to the bottom of the planter without it running out! Try it you will like it!