Step 1: Prep the Soil
Start preparing the ground at least six weeks before planting. Clear the site of perennial weeds, then dig a strip the length of the hedge and 3–4 ft (90–120 cm) wide. Fork plenty of bulky organic matter (such as garden compost or well-rotted manure) into the trench as you go.
Step 2: Dig a Trench
Set out a line to mark the edge of the row(s) of plants. Dig a trench along it for bare-root plants; you can dig individual holes for containerized or root-balled plants after marking out their positions. Use canes and a ruler to mark out the planting intervals, either in a single row along one line, or in two staggered rows, laying canes 18–24 in (45–60 cm) apart as a guide.
Step 3: Measure Plant Depth
Plant at the original planting depth—this will either be the top of the rootball, or to the soil mark on the stem of bare-root plants.
Step 4: Firm Soil
Return the soil to the trench, and firm it well using your heel, at the same time creating a slight dip around the plants.
Step 5: Water the Roots
Water the plants thoroughly; the dip around each plant will help direct water to the roots, where it is really needed to help the plants establish.
Step 6: Cover with Mulch
Place a thick mulch of well-rotted manure or compost, or of shredded bark, around the plants, making sure it stays clear of the stems. Alternatively, lay landscape fabric in strips on each side and cover with bark chips.
If you have just bought a container-grown shrub, first water it well by plunging it in water for about an hour, then allow it to drain.