Ceramic Pots – Need to Waterproof?

Q: We recently purchased ten very large ceramic pots. We plan to have evergreen plants in the center with seasonal annuals around them. Should we waterproof them somehow?

A: My friend Mildred Fockele oversees dozens of large containers at the Atlanta Botanical Garden. She says her staff uses liquid roofing tar inside their big pots, spread with a heavy brush. She warns that while doing the chore everyone wears clothes they can discard afterwards due to the inevitable tar stains