Question
Do certain lava rocks contain enough acid in them to help roses grow and keep the soil acidified enough to help them along.  

Using them as a mulch I would think would help with the soil acidity but needed to find out.

I live in Dallas area where we have clay gumbo soil.

Answer
Hi Glenn;
I live in Irving, and have grown roses for a long time, but never heard of them needing acid.
I have that darned clay soil too, or rather I DID have.
I tilled enough stuff into it to make good healthy soil, and I have been on an organic program for 8 yeras.
Before that, I broke my body and my bank account, trying to have a good lawn.
Now I do less than 10% the work, and spend hardly anything, and have a great lawn. No incests,not even any aphids on my roses, and no weeds.
the healthy enviornment fot toads, lizards and grass snakes and beneficial insects, eat ip all the pests.
I don't even get grubs.
I watched Howard Garrett's show a couple of months ago, and he suggested using alfalfa tea,especially for blooming plants. It is supposed to make them produce more and larger blooms.
I had to fo to a feed store to get alfalfa meal, but I did, and made the tea, used it on everything that blooms, and added it to new plants I was potting.
I just threw about half a handful on a florabunda in my front yard, and the new leaves were twice as large as the old ones.
It seems to improve everything.
Lava rock and sand is full of nutrients,
The lava sand adds nutrients to the soil faster than the rock would.
My husband picked up the lava sand at Walmart.
When bananas are too ripe even for banana nut bread, I put them in the blender with water and make a tea, and feed my roses with it.
It is a good source of potassium.
If you would like more about organics, write me, I am happy to share what I have learned.
If you would like to check out howard Garrett's website, it is     www.dirtdoctor.com
Charlotte