Hi Dana.
@bloominholes2fill
You can use Thompson's water seal or tung oil to help water seal terracotta containers. This link has some pretty good info on waterproofing and sealing ceramics,etc.
http://www.bigceramicstore.com...
I have a couple large unglazed terracotta containers that I have had for a number of years. I use them for annuals.
The first time I poured some of the sealer in an old clean coffee can and used a paint brush to coat the pots, inside and out side. When I replant the containers, I wipe the exterior of the pot to make sure it is clean and apply another coat with a brush. Doing the outside helps protect the pot from pitting and UV rays.
