Somehow, in a conversation with a co-worker, he confessed that he no longer "did mulch". I wasn't quite sure what he meant. Was he letting the ground go bare? No! He had "mulched" with rocks, specifically lava rock. The permanent mulch!
I humbly submit that rocks are not mulch, rocks are loose paving. Show me a garden with rocks for mulch, and watch me run the other way, fast! When you have rocks, it is difficult to replant anything where those rocks are. And, no matter how hard you try, the rocks end up outside of the bed and in the grass.
And rocks are so permanent! Just ask my sister. She lives in the family homestead. Back in the 70's, before you could order truckloads of organic mulch, the "fashion" was to put rocks around all the landscape beds. So, that's what my Dad did. He ordered a big load of rocks and had all of us "kids" help him spread it around the shrubs around the house. Now, my sister is dealing with these rocks. She can hardly plant anything because of the rocks. And, over time, the rocks have shifted around and thinned in some spots, and spread into the grass.
There is one bed in front by the sidewalk to the front door where they tried to dig the rocks out so they could plant some new shrubs. They didn't know where to put the rocks, so they hauled them over to another side of the house and dumped them. It seemed like no matter how deep they dug, they kept running into more rocks. Finally, they just gave up and planted as best they could. Then one spring, my sister got tired of looking at the those old rocks. So, she ordered up some hardwood mulch and just put it on top of the rocks. It looks good, and is more the style of today's gardens, but we all know that beneath that mulch are rocks, and more rocks.
We had a neighbor around the corner, and this woman bought some of rocks that were really white and shiny, almost like marble chips. She put them in a bed with a path in it that led up to her front door. The path wasn't really a concrete sidewalk, but a bunch of gray stepping stones. She put up a sign to ask people to "please don't walk on the rocks". I guess she didn't want them to get dirty or get kicked around unnecessarily. I can only imagine what she did to keep the leaves off in the fall, so there would be no organic matter build up or dirt in with her white rocks.
Anyway, that's just my opinion that rocks aren't mulch. I know others like to use rocks, and that's fine with me. I just find them to be too permanent. I prefer cypress mulch around my shrubs and trees, and cocoa hull mulch or compost from the compost bins around my perennials and vegetables, but that's just me.
(Don't get me started on mulch made out of old tires that are cut into little pieces and dyed to look like cypress mulch!)