If you have to plant during warm weather, set the plant's rootball in a water-filled galvanized tub to soak it thoroughly while you prepare the planting hole. Then plant in early evening after temperatures have cooled down. After planting, water well.
In fall, most perennials, shrubs, and trees are sold in black plastic containers. To prepare for planting, slide the rootball out of the container and rough up the roots on the sides with gloved hands. Snip off any roots that encircle the outside of the rootball or form a dense mat on the bottom.
1. Dig a hole three to four times as wide as the rootball and the same depth (in mild climates, the top of the rootball can sit about an inch above ground level to allow for settling). Set the plant in the hole.
2. If your native soil is loam and drains well, backfill the hole with it. If your soil is very sandy or is heavy clay, mix the backfill with an equal part of compost. Add the backfill in stages, firming it around the roots with your hands.
3. Build a berm of soil around the plant to form a watering basin. Irrigate gently. Spread a layer of mulch around the plant, keeping mulch several inches away from the stem or trunk. Don't fertilize until you see new growth emerging in spring.
BALLED-AND-BURLAPPED SHRUBS AND TREES
In the Northwest, some landscape plants (often large specimens) are dug from growing fields with a ball of soil around their roots; the rootball is then wrapped with burlap or similar material and tied with twine. Here's how to plant them.
1. Measure the rootball from top to bottom. In rainy climates, dig the hole a bit shallower than this length so that the top of the rootball is barely above surrounding soil. (In cold climates, the rootball should be level with surrounding soil.)
2. Untie the covering. If it's burlap, it will eventually rot; spread it out to uncover half of the rootball. If it's synthetic material, remove it. On a windy site, drive in a stake upwind of the rootball. Fill the hole with soil to within 4 inches of the top; water gently.
3. Continue to fill the hole, firming the soil as you go. Make a berm of soil to form a watering basin; then thoroughly soak the rootball. If you added a stake, loosely tie it to the plant.