"Cat" wrote in message
...
I'm in the process of turning my [long, narrow and shady] back yard
into something more interesting than tons and tons of vinca - and
I'd like to build up part of the garden into a mound about 10' long
by l2.5' tall. Is there a more efficient way than buying a ton of
dirt?

A 'mound' 10 feet long by 12.5 feet tall is not a mound at all - it is an
unstable pile of soil that will not maintain those dimensions. I assume
there is a typo here and the 12.5 feet is really more like 12 inches, in
which case you have pretty reasonable dimensions for a small berm.
Generally, berms are constructed with a slope of no more than 5:1 - steeper
slopes look awkward, specially in small gardens, and will require some
additional form of stabilization to prevent erosion or sliding.. This means
that for a berm 10 feet long/wide, the maximum height you should attempt to
achieve will be 24 inches, but I have found that a slightly gentler slope is
easier to plant and maintain and looks most natural.

A very easy way to achieve this is by removing sod from an area in your
garden and laying it upside down (root side up) in the location of the berm
to the desired height A light layer - 3-4 inches - of decent soil over the
top and you will be ready to plant. If you have no sod to remove for the
base, then you are looking at bringing in a quantity of soil. Assuming the
berm will be about as wide as it is long, about 2.5 cubic yards should do
it.

This link may help:
http://www.sustland.umn.edu/implement/soil_berms.html

pam - gardengal