On Wed, 01 Sep 2004 10:47:21 -0400, Terry Gwazdosky demiurge at
adelphia.net wrote:

This spring I planted grass underneath and around a tree in my front
yard with a sun/shade mix. The grass sprang up quickly and seemed
healthy most of the summer.

Well, it's probably not your sun/shade grass mix then.

Over the last two weeks the grass
has almost completely disappeared in the shaded area leaving me with
just dirt.

Your problem is due to one or more of the following:

Even shade grasses need a minimum of a couple of hours of sun a day.
The tree may have leafed out more since the spring and grown
additional limbs. Or the angle and direction of the sun has since
changed; not allowing as much sunlight to get under the tree, etc. If
the area doesn't get much sun, limbing up the tree and thinning the
canopy on a semi-regular basis will help.

Drainage could be an issue. Too much water in a shady area isn't good
for grass and can lead to lawn fungus, gradual decline, and so on.
Pruning the tree to allow more sunlight in can also help in this case
unless the drainage is extremely poor.

If you've got a lot of surface roots, it will be hard to grow grass as
the tree roots will always suck the moisture and nutrients out of the
soil. You can compensate somewhat by watering and fertilizing more,
but it will mostly be a losing battle.

Until you figure out the cause and correct it; not much point in
reseeding.