Planting Basics
New research on trees has changed the traditional method of planting, where a hole was dug slightly deeper and wider than the rootball or container. Scientists now recognize that tree roots are naturally shallow and wide spreading, with the majority found in the top 18 inches of soil.

 

Balled or containerized trees: Choose a sunny location for most species. Some trees, like American beech, sugar maple, and dogwood, can tolerate various amounts of shade. Handle the tree by the rootball, not by the trunk or branches. Avoid planting species that will grow tall beneath utility lines.

Keep the rootball moist and the tree in the shade until it is time to plant. Burlap should be loosened at the top or removed completely.

Dig a hole no deeper than the rootball, but much wider—at least twice as wide, but three to five times is best—so the roots can spread quickly into the loosened adjoining soil and anchor the tree against winds and storms.

 

 Figure 1

Fill the hole with the soil that was dug up unless it is heavy with clay. Too much clay in the hole acts like a giant pot, forcing the tree’s roots to circle round and round and never break through the sides to new soil. If the soil does have a lot of clay, amend it with compost, aged manure, or peat. Do not use sand, which can bind with clay to create a rock-hard cement-like mixture.

Water the tree immediately to provide moisture and settle the soil—avoid packing down the dirt unless it is very fine sand. Mulch is a good idea, but spread it no thicker than three to four inches and do not pile it up against the tree trunk.

For the first week after planting, lightly water the tree daily. The second week, water every other day. Taper off eventually to once a week if needed. The goal is to get the root system large enough for the tree to survive on natural rainfall.
Figure 2

Bare root seedlings: Bare root trees should be planted as quickly as possible. Remove any packing materials and soak the roots in water for three to six hours, then dig a wide, shallow hole that will allow the tree to stand at the same depth as it did in the nursery. Leave a cone-shaped mound of dirt at the bottom of the hole to encourage roots to grow downward and outward.

Follow the instructions for planting a containerized tree, but water more generously every day for up to 10 days before tapering off. Some experts recommend dipping a bare root seedling into a water-absorbent polymer gel before planting, or mixing this gel (available from nurseries) into the backfill soil.

Figure 3

Staking and fertilizer: For most trees, staking is not recommended. If the tree trunk is not sturdy, however, use two stakes, one on either side of the tree, for the first year only.

Avoid fertilizing a tree until late spring of the second year following planting.

Soil and space: For trees to survive to maturity, the focus needs to be on the soil and the planting space around the tree. Sufficient amounts of good soil are needed to store and convey water and nutrients to the roots. In developing roads, sidewalks, building sites and parking areas, the good soils are typically removed during grading. Special attention has to be given to reintroducing good soils for trees to be planted. The critical need is to create enough space when planting trees so that their root system can spread. Three typical conditions to enhance Knoxville’s streetscape include:

  • In usual circumstances, the soil surrounding the plant pit will allow for root penetration. In such circumstances backfill with the old topsoil, a mix of the old topsoil and other organic material, or new topsoil.
  • Where there is surrounding clay, the planting pit needs to be large and filled with equal volumes of the original soil, compost or organic matter and sand.
  • In creating planting pits in sidewalks, parking areas and similar “hardscape,” a minimum of 2’ of fill (a maximum of 3 feet) is necessary, including (by weight) less than 27 percent clay, at least 50 percent of 1 millimeter sand and 5 percent organic matter (which is 20-35 percent organic matter by volume).

large planting pits

The larger the planting pit, the better

Another approach in such areas is the use of “structural soil” that is composed of a mixture of angular crushed stone, soil and an adhesive that maintain pores within the mix for root growth and water and air infiltration.

The general area requirements recommended for each class of trees to survive to maturity are as follows: Small Tree Group: 100 square feet Medium Tree Group: 225 square feet Large Tree Group: 400 square feet

A time for planting: Generally, late October to mid-December and March to May are recommended. Fall planting must be undertaken before soils become so cold that roots do not have a chance to grow. Spring planting should be undertaken before leaf or flower buds open. Extension agents, nursery personnel or similar professionals should be consulted with regard to the planting characteristics of individual species.