Digging a hole may not seem like a big deal, but it is one of the critical factors in having a successful plant after the process is over. So read on.
Preparing the Area
No matter what type of soil the shrub has grown in before it arrives in your yard, it has to adjust to the type of soil you have there. Consequently, planting techniques are designed to encourage them to do this. Remove and recycle all lawn sod from the planting area.
Remember, most shrub roots grow outward, within 8 to 12 inches of the soil surface, rather than down into it. The best way to encourage roots to venture into the new soil beyond its hole is to loosen the soil over a circular area beyond the hole roughly 3 times the width of the rootball. Use a hand core aerator, or a pitchfork to punch into the soil and rock back and forth to loosen it. Tilling is not necessary and may even disturb roots from nearby plantings.
If the soil is very compacted, heavy clay or very sandy, work some chopped leaves, peat moss or other organic material a few inches into the loosened soil. Tender shrub root tips will be inclined to grow outward toward this aerated, nutritious neighboring soil and can penetrate it more easily. The extra time and labor required for this extensive preparation is not always necessary or practical. If you dig the hole and plant properly, most shrubs will manage fine if you are not able to manage more.
Establishing the Correct Hole Depth
The key to planting a shrub properly is digging a hole the correct size and shape. The correct depth is critical. If a shrub is planted too deeply its roots will not get enough air, and eventually the shrub will suffocate.
Dig the hole as deep as the height of the rootball. Locate the soil line on the shrub’s stems where the roots begin to flare out and measure from this point to the bottom of the rootball. Untie the burlap from the base of the trunk of B & B shrubs and scrape away any excess soil from the top of the rootball to expose this juncture for measuring. Containerized shrubs will already be at the correct soil depth, so dig their hole to align their soil surface with that of the surrounding soil. In very clayey or pooly draining soil, plant shallower so the top of the rootball is 3 to 4 inches above grade.
Because it is essential that the juncture of the shrub’s stems and root system remain at or just above the soil level, do not fill it with any loose soil, peat moss or fertilizer. The shrub may sink deeper in the hole later when any loose material under it settles or decomposes. Bare root shrubs are an exception to this rule.
Establishing the Correct Hole Width
Make the hole the correct width and shape to facilitate planting and to encourage roots to grow into the surrounding soil. Dig it at least twice as wide as the container or rootball. Slope its sides so that it resembles a saucer. This gives you leeway to maneuver the rootball for correct placement and to remove some of the burlap from a B&B shrub.
Research and experience have shown that holes with vertical sides act like containers. Shrub roots feel confined and tend to grow in circles within the restricted space, eventually girdling themselves and killing the shrub. If your soil is heavy clay or very compacted, score the sloping sides of the hole with a trowel or edge of a shovel or spade to make indentations to further encourage root penetration outward. Remove any loose soil that may fall into the hole.