Our first big test was if we could keep trees in pots over the winter, which would give us more height and dimension in the space. Once we got through the first winter, we decided to edit the plan and plant the upper tree directly into the hillside, which made a huge difference for blending the separate spaces.
The site was mostly fill gravel around a septic tank, so we dug down 12-18" where we wanted planting areas to go, and hauled the debris off site. Then we brought in bagged soil and compost, and blended them in place, making sure the plants had the best chance possible to succeed. During planting, we brough a mix of plants that we knew would work well, and arranged on the fly. We then finished off with mulch and a heavy watering.
We expect the summer sweet clematis to start taking over the trellises in the coming years, and are working with a local stone mason to replace the green septic cover with a large stone, more effectively hiding that eyesore.