Roger wrote:

Thanks to all. Unfortunately I did not make myself clear.
I do not really care about growing anything, even though I will try the
local ag agent. I would be happy with pine bark, pebbles or whatever.
Anything to stop soil from washing away. BUT it can not be too heavy or
the weight will kill the tree by smothering the roots.

Now that you've cleared that up, here is another plan.
I've used heavy duty dark grey or black fiberglass landscaping cloth from
home depot, pinned down with plastic spikes made for this purpose.. It
kills existing weeds by starving them of light, but allows warmth and rain
to percolate to the roots of the overhanging tree. It also acts like a
mulch, so new weeds will not get a foothold. Once you decide to plant ground
cover, you just cut X-shaped slices and fold back, and plant, then refold
the cloth up against the plant.
Be sure you get the *heavy* grade of cloth, as the light stuff, which is
trashbag style poly film with perforations, is useless. The heavyweight
comes in big rolls and is about 1/8th inch thick and looks like a bedcover
or blanket, is made of glass felt, and resists rotting and tearing. If
after installing, you don't like the look of it, you can scatter pine
needles or dry hay over it until you decide to plant.
Works like a charm.

Thanks

LB