I believe you are referring to how Earth Boxes and their homemade equivalents are fertilized.

The Earthbox idea differs from other self watering containers in that the potting mix is covered with something water cannot penetrate.

The fertilizer strip is simply regular granual fertilizer applied on top of the mix in a strip. The plants in the container are arranged to be as far away from the fertilizer strip as possible.

This wouldn't work well with an uncovered container as the fertilizer would be washed via rain and waterings into the soil too quickly. With the cover on the fertilizer slowly breaks down and enters the mix.

The earthbox instructions call for 2 cups of synthetic fert or 3 cups of organic so it's far too much to add if it is going to be watered into the planting media.

Thanks, actually I was planning to follow the instructions that jmalt had posted which calls for the tops to be covered with a black tarp similar to the earthbox. Though now that you mention it he didn't indicate whether they were water proof tarps or not. I was going under the assumption they should be rain protected else it would seem somewhat self defeating not to.

I'll keep researching, I really am interested with this type of container gardening.

You might like to go over to earthbox.com and read the instructions they have online. The homemade versions work essentially the same way.

Hi Rich,

I am making diy earthboxes too this year, and in my research I have learned that a common fert used in them is TomatoTone. It is granular, and (obviously) is for tomatos. I might like to grow some things in addition to tomatos though, and I am guessing I'll just use something that is all purpose.

The main idea is that you don't want something that is water soluable, like something granular that you would mix with water and apply as a liquid.

What just exactly is a "self-watering" Container?

A self-watering container is just a container with a water reservoir underneath the potting medium ("soil"). There is a wicking system that allows the "soil" to draw up the water as needed. It basically buys a little time in between waterings, but you still need to give it all the water the plant needs. So if a tomato plant needs a gallon of water a day, instead of giving it a gallon a day, you can pour in 4 gallons one day and wait a few until you water again (depending on the size of your reservoir of course.) I had a container with a 4 gallon reservoir and 2 tomatoes in it last year, and for much of the summer it seemed like I didn't have to water at all. But there were a few weeks where I was doing it every other day, and maybe even every day. So hard to remember...

Oh - just thought I'd give you some brand names. Earthbox and Garden Patch are self-watering tubs with mulch covers that are pretty utilitarian looking but seem to have great yields. Gardeners Supply also has tons and tons of self-watering containers, from pretty decorative ones to ones that are like the utilitarian plastic tubs. I used the latter last year for my tomatoes with great success.