It appears as though your plant is suffering from an extreme accumulation of soluble salts in the media surrounding the roots. I would flush flush flush flush (getting the idea?) until you're sure you've rid the soil of the excess salts. Imagine how curing salt 'pulls' the water out of meats and fish ..... and you're imagining what's occurring with your plant. It cannot take up water because there is a state of isotonicity, or even hypertonicity, between the solute level in cell cytoplasm and the soil solution. Al Here is a link that might be useful: Watch the movie

We put down red lava rock in a 4x30 bed last year instead of the annual red pine mulch that bleached out and burns up in the Florida sun. We completely removed the mulch, dug down about a foot and removed any weeds. Put down one of the most expensive landscaping cloths, not black plastic, as there were already plants in the bed. Black Edging and 3-4 inches of lava rock put down. Within 1 week there was St Augustine grass coming up thru the fabric and rock in the center of the 4 ft bed. The stuff is a nightmare to try and maintain. You’ll destroy the fingers of any garden gloves weekly. It DOES RETAIN HEAT and my plumerias lose leaves daily from being baked. It’s also breaking down, with no car or foot traffic in the bed and there’s almost an inch of red rock sand now trapping weed seeds also. We’re in the brutal heat/humidity part of the year right now. In a couple of months, we’re removing it all. Not sure what the replacement will be.

It's often hard to get the right mix and technique when using regular mortar to make is stick properly. The easiest way to get around this is to use fortified thinset mortar. Buy it in dry form with either the fortifier pre-added or use the kind that takes a liquid fortifier - do not use the pre-mixed kind in the plastic containers. Thinset has a kind of glue in it, in additon to the mortar. It's a little messier to work with and somewhat more expensive, but you will find that it will stick the lava rock on really well.

I was going to say, just take it off the dang thing and replace with siding. Its just a veneer and often only on the one side of the house, not relating to anything else. Then do raised beds and stairway in stone in front to ground the house and give appearance of solidity. Create a good size landing in front of the door - at least 3-4 feet out, with the 4 steps going down between the raised beds on either side. The beds should extend at least 6 feet out to allow for a generous display of perennials or flowering shrubs. If room add small ornamental tree closer to the street, to the side of the house. Oh well, a project for another time maybe. IMHO small modest houses always benefit from lush cottagey plantings - - you could get geeky and choose popular 1950s era flowers like bright zinnias and red carnations