i have posted before about coating glazed urns inside with roofing tar-to make waterproof.i think you can use the same method for terracotta.you can read about my method at www.cottonarboretum.blogspot.com OR see below: Making glazed pots into FOUNTAINS, and cleaning them Posted by arbo_retum z5 ,WinchstrMA (My Page) on Mon, May 1, 06 at 14:38 SEALING/WATERPROOFING THE POT: We have converted three large chinese red glazed and blue glazed earthenware pots- to fountains. we have plugged up their bottom drainage holes by putting black duct tape underneath the hole, and then from the inside of the pot, filling the hole with 'Bondo'. after the Bondo has dried, we apply a thin opaque coat of roofing tar to the entire inside of the pot, up to the glaze. once that has dried thoroughly, the pot is ready to put in place,fill with water , and insert a pump, which we put on bricks.over the pump's water 'nozzle', we then put a piece of tight-fitting black pvc pipe , cut long enough to make a nice fountain but not too high or low. (this height issue and the water fountain 'look' that you want are what takes all the tweaking.)you may also want to play with various pump sizes. ELECTRICITY: even though electricians don't recommend this, we then plug in the pump to an electrical outlet using outdoor green electrical wire- like you use for outdoor xmas tree light.we don't bother to bury the wire(unless it crosses a path); we put mulch/shredded leaves over it to hide it as needed, and we do not take it up for the winter. the one drawback to this system, where we plug up the hole, is that you can see the electrical wire that hangs outside the pot, but that can sometimes be camouflaged. we use sealed pots for fountains but also for growing waterplants (cannas, elephant ears, water iris, waterlilies). we bring in our pots onto a screened porch but in z.5 they can be turned over and left outside if they are raised up off the ground. CLEANING: the ugly white milky lime deposits we eventually get on the outsides of the pots-i clean in the fall or spring.we tried Lime-Away but it didn't work well. Instead i devised this system: I use XXXX grade-the finest- steel wool dipped in BOILING vinegar(i plug in an electrical fondue pot next to the pots i'm cleaning to keep the vinegar boiling!!)I go over the outside glaze once-gently but firmly, keeping my st.wool very wet w/ the boiling vinegar. then i let the pot dry. if it still has lime, i go over it again and let it dry. then i coat the pot with a thin coat or 2- of butchers wax, buffed with towelling. the pots are placed on columns/pedestals in the gardens. i personally feel every garden needs some form of water. what a difference it makes.our gardens are on a busy main street so we have fountains and waterfalls spread throughout the garden. the sound is soothing and inviting and helps mask the street noise. i hope some of you find this info useful! best, mindy

I'm also a huge advocate of leaving unglazed clay in its natural state... it's healthier for the plants. It not only allows gasses to pass through its porosity, but it also helps accumulated salts to leach out. You'll notice that white crust that can appear around the rim or sometimes on the body of the pot. If you sealed the pot, those salts would be reliant upon frequent leachings with clear water to be removed. I don't know why anyone would want to spoil the healthiness of unglazed clay... if you need more moisture retention, work with the medium, not the pot. :-)

I don't think the plumbers putty will stick to terra cotta. I have seen a good plug made from a rubber plug that enclosed the cord. You might try a cork plug cut to hold the cord and coated with liquid latex (found at most craft stores). You could also make a boot from a piece of scrap EPDM or a cut up innertube around a cork trimmed to fit the hole. Gorilla Glue foams up like Crazy foam and you could use it to hold the cord in place and stop any leaks. Lots of different ways to do it. Sandy

Well...I have fushia, coleus, potato vine, licorice hanging-thingamajig, wave petunias, salvia, purple fountain grass, verbena and dusty miller...those are the ones in pots in front. In back I have potted up fragrant ginger (a new thing for me), a tropical Hibiscus, a couple of banana plants, stevia, and some other stuff...can't remember as I was outside all day!! In the ground with the black larger pots I put my astilbe, bleeding hearts, hostas, ferns, lungwort etc. I also built some raised beds and lined them with plastic too for veggies...to hold the mositure better. Oh...I am going to try brugmansia too. Most of the other stuff, I am trying to pay attention to the "zones" of the yard....areas that stay more moist...areas that are dry. I am not sure I answered your question or not...LOL I am just a ramblin'