is this moss?

Please see attached pic of the bottom of the trunk of my bouganvillea. It appears to have moss or something that is green covering parts of the base of the trunk. It's been forming under the rocks. Tried moving them away so the sum would dry it out, but it's still there. Also tried scraping it off, but it persists. Does anyone know if this is moss? Is it harmful? Remedies?
- thanks

I see the moss, the green, but it's the white and yellowish areas that most concern me. From the pebbles and the look of the trunk, you have this in a pot, and are watering with tap water and using a liquid fertilizer. The pebbles are probably a more recent addition because I'm not seeing the accumulated salts on them, too.

I would suggest repotting, or at least removing any loose soil from the surface and replacing with fresh potting soil, then watering with rain water or aquarium water. Distilled or filtered would also be okay. You might want to switch to fish emulsion for fertilizing, too.

For what's already on the trunk, you could gently wipe with a damp cloth, but if you scrape too hard you'll damage the cambium and that could kill the plant. The accumulation of salts is not a good thing for a softer bark like that on a bouganvillea. Not for any bark really, but this could rot the bark and kill it eventually.