The Volcano Planting method by Andrew Van Cleve
I've been doing this for around 20 years and almost every plant I've used it on has thrived.
When I did it at Yonder Farms we were working behind a stone wall. First we dug out most of the soil behind the wall.
Then we put large potted plants in place.
We surrounded them with Volcano's of soil.
Then filled in the vacant space with mulch.
Water and fertilize regularly (they will dry out faster this way).
As the mulch sinks add more mulch.
At Azalea House Flowering Shrub Farm I was planting perennials.
I covered an area ten inches deep with bark mulch.
I dug out holes in the mulch put in the perennials and filled around them with ideal soil.
Water and fertilize regularly (they will dry out faster this way).
As the mulch sinks (so the volcano sticks up above the mulch) add more mulch up to the top of the volcanos.
After several years the perennials had sucked themselves down into the ground and the soil was ideal everywhere.
Since then I have lined out hundreds of own root roses, lilacs, perennials and rhododendrons using this method and so far had marked success. Come talk to me about this method at my plant sale May 15 to July 4; 10 AM to 2 PM