I use plastic liners, or just don't place plants on wood furniture.

I water plants in a sink and drain well. I then set them on the round absorbent stone coasters with cork bottoms to protect my my granite counter and glass table. (just in case) I keep floor plants off my marble floors on the clear "plates" made to hold planters. I have learned the right amount of water for those plants after mopping up excess water off the floor. I also have one floor plant and two table plants in the cheap plastic container they came in and I set it them in a little bit bigger, nicer pots with no drainage holes. Now when I water, I have no worries about flooding. Any excess water, will now "self-water" the plant from the bottom! Just don't leave too much in there. Indoor plants don't need as much water as you'd think unless they sit in direct sun or near an air vent.

All of the above suggestions:
Plastic liners, ceramic plant pot saucers, sandstone with a cork bottom under the plant saucer, a rag in your hand when you water, and don't put plants on extremely valuable furniture (monetary or sentimental).

Thanks for the tips. All my plants are on ceramic saucers or ceramic cache pots so I was surprised to see damage.

A similar but puzzling thing happened to me. I had a plant on a runner that was on a buffet. The plant was in a clay pot that was placed inside a metal pot. I also had a plastic bowl in the metal pot to catch any water. When I pulled up the runner there was a white ring where the plant had been. I noticed that the metal pot felt cool. My analysis suggests that as the overflow water in the pot evaporated it cooled the metal enough that water from the room condensed on the bottom of the metal pot. So now I put those ugly cork coasters under my plants. Fortunately the buffet already had some bad scratches so I always keep a runner on it.

I should add that a good way to protect wood is to buy glass to fit the top of your furniture. It isn't very expensive to do so.

That's helpful. Maybe it is condensation or the ceramic saucer is unglazed or not fully vitrified. Maybe I'll have a couple pieces of glass cut to fit the bottom of the pots I'm worried about. I have a big ficus that I keep in the original plastic container it came in and then put it in a (large) ceramic cache pot. I wrapped a garbage bag around the plastic pot to prevent any over-watering from hitting the cache pot and haven't had a problem.

Hi Karelian, where do you buy the plastic tile?

I use clear rounds of glass under all ceramic pots I had specially cut to match the bottoms of planters that aren't footed.

Mike Slater: I think I bought it in Office Depot. It comes in rolls. Mine is blue. It's original purpose is to mitigate vibration and noise. I've had the same roll for years. It doesn't seem to wear out.

Thanks! I'll try that and if I can't find it, I'll go the custom cut glass route.

Thank you all for the helpful (and fast) responses!

Besides cork coasters, I have found that if I water plants in sink or shower, and allow to drain well, much less problems.

Then I put something to create large air space between bottom of plant and bottom of container. I have used lumber cut to size or even cut up stiff foam pieces (the kind that electronics are packed into boxes with).

Thanks. A few of my plants are simply too big to move for watering. It seem the key is air circulation and the proper amount of water to reduce self-inflicted problems.

Even glass can cause problems if it sticks to paint or varnish. You should use silicone pads in the corners between the glass and the furniture or windowsill. The condensation under plants is hard to beat. I am still looking for the best way but think good drainage, avoiding spills, cork or footed holders, and moving the plants around periodically may help.

I put 4 pots of orchids in a 24" long plastic window box (no drainage holes). It's a bit decorative, keeps water off the table, is high enough to place a "spacer" under the pots, and keeps the pots from tipping over. I placed an old tea towel under the planter so I can slide it around to dust.

Most of my houseplants are sitting in plastic drain things made for houseplants. I have put them on runners with no problem. Some of my plants with no drain holes are sitting on a ceramic tile or a round mirror with tiny feet. No problems there. I have houseplants on end tables with a plastic table mat under them for color....these are plants with holes sitting in a ceramic pot with no holes. Depends a lot on your plant....I have maidenhair ferns that need a lot of water...they are in pots with drainage holes, sitting in pots without holes or in deep saucers so you can see that they are not sitting in water and over watered. Glad you found the solution for removing the water mark.

I have the pots inside pretty deep bowls or pans to catch extra water and then the entire thing inside baskets that hide it all. You could use a bigger ceramic pot as well. I also water some of them in the sink.