Answer: Your plants will remain healthier if your terra cotta pots have drainage holes in the bottoms. The problem with pots with no drainage is that water will collect on the bottom and become stagnant. Even with a layer of rocks or gravel, water will still be trapped, will still become stagnant, and can contaminate the potting soil, which will eventually affect the roots of your plants. If you're determined to use the terra cotta pots, even with no drainage holes, how about putting your plants into plastic containers with adequate drainage and setting those pots into your decorative terra cotta containers? This way you can periodically lift the plastic pots and dump the accumulated water out of the terra cotta pots. Be sure to set some stones in the bottom of the terra cotta pots to keep the plastic pots from sitting in a puddle of water.
Best wishes with your container garden!
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