In an established keyhole garden, how do you maintain the compost circle? Remove, stir, add to it? Seems like it would eventually become overstuffed or all the good stuff stays at the bottom.
Composting in a keyhole garden is no different than making compost anywhere else. You still need to make sure there is about a 50-50 mix of brown and green material and that the pile stays about as wet as a wrung out sponge. If you don't turn it to aerate it, it takes longer to biodegrade. As with all compost the smaller the organic particles, the faster it biodegrades. The easiest way is to just keep adding all your organic waste until the end of the season then let it break down until the next spring. In the spring, rake off the top few inches that will not have broken down yet (and use them to begin a new pile). The organic material at the bottom of the pile should be nicely composted and ready to use on your garden.