Locate suitable planting pockets (areas between large roots) beneath the tree(s) for shade-tolerant shrubs and perennials. The farther from the tree trunk you plant, the greater the number of available planting pockets. Avoid the roots present on the surface of the soil. Lay out the containerized or bare-root plants, arranging them in groups of three or five.
Dig planting holes slightly larger than the nursery pots that contain the new plants. If you encounter roots, move the planting holes to accommodate those roots. Before installing plants, "water in" by filling holes about half full with water. Install plants and fill holes, firming the soil at the end. A trowel may be more useful than a spade for planting bulbs.
Water once again and mulch the new plants to conserve soil moisture. Protect new plantings against animal predators, if they are present, with barriers or repellant sprays.