What size containers are you talking about, Joybell and Lynn? Asking about both width and depth.

What size clay pot would it take to keep, say, a 12-16 inch pot of impatiens, caladium or coleus watered for a week in high summer? (After experimentation, Lynn, I accept that I don't have enough sun, and especially don't have enough time to do much with veggies in pots in summer.)

Never had much success with the spikes in upturned plastic bottles. Tried it for a few years with tomatoes when I lived where I had sun. No matter how much amending here, if you are growing plants in the ground, the soil is clay, and the spikes clog, even in clay loam.

Plus, they are butt ugly:>)