On Wed, 30 May 2007 22:03:13 -0400, James no wrote:
I have seen what looks like crushed red brick in commercial restaurants such
as McDonald's etc. It may be a lava type product, but the last time I
noticed, it looks like crush brick pieces. It is a reddish color, and it
looks really good where I have seen it.

It usually is a lava, and it is, imho, ugly. Terribly ugly when it's not
like the native rock of the area.

The problem (and my question) is whether or not weeds are a big problem if
you use that product as a mulch subtitute.

Weeds (and other seeds) require several things for germination:
1) a suitable growing medium
2) enough water
3) light

The easy way to prevent weed growth is what agronomists call "canopy
closure" -- plants growing so densely that light doesn't reach the soil.
Or starving the surrounding soil of water, which you're not going to do
during the establishment phase of the plantings. 3-4" of coarse rock
isn't likely to do much unless it's well packed. Doesn't sound like
you can provide that. Red light of the wavelengths that trigger germination
can penetrate 18" of some soils.

If you're dealing with a slope so steep you can't keep mulch on it, you're
going to continue to have erosion. Were it mine, I'd probably do some
mini-terracing and use an organic mulch with a tackifier until the plantings
are dense enough to hold the soil.