Last fall we removed all of our oregon grape that has been growing for over 20 years to re-landscape a flower bed in our front yard. We put mulch on the bare ground to sit over the winter in hopes to start planting this spring. Now we have several mushroom 'colonies', is what I call it, breaking through the soil, but they are only coming through on half of the 5' x 12' area. I have pulled out the 'first round' of mushrooms, and now twice as mony are coming back, in the same area. How can I get rid of these mushrooms so that we can plant our new daylillies and spirea? I might also add that this area has not received alot of water, although it is next to our driveway where we shovel the snow.