I want to try to create something I saw in a*home & garden show but have never done landscaping with boulders before.* I'd like to plant a birch tree, several bushes & perennials all about 3 feet above ground and incorporate 18 in boulders within it.* What material do you use to backfill?* Compost?* Also is there anything used to stabilize a new tree?* I've only planted them below ground (ie compacted soil) and I'm wondering if the compost would be too light to support a tree root ball.
Just using compost would be too unstable for a berm.* You will need a combination of materials.* Here's how to build a berm.* You can always add 3" to 4" of compost to the top of the soil and mix it in the entire planting area once the berm is constructed.
You can stake your trees for 6 to 12 months.* They will need to sway a bit in the wind to strengthen their roots.