Tips For Selecting Trees

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Select trees and shrubs for quality, which can be determined through careful inspection. Evaluate root ball size and structure; trunk form and strength; branch structure; and evidence of injury, disease or poor cultivation methods.

ROOT BALL CHARACTERISTICS: The shape, depth and size of a tree's root ball is determined by the way the tree was produced in the nursery. Trees grown directly in the ground are field-grown. Trees are also grown in containers of different sizes, shapes and materials that affect the structure of the root ball.

Field-grown trees are strong and sturdy. They are good choices for evergreens and larger trees and compared to trees grown by other methods, the root ball of a harvested field-grown tree is larger and contains more roots.

The root balls of field-grown trees are also much heavier than those of container-grown trees, making them significantly harder to handle. When field-grown trees are harvested, burlap is wrapped around the root balls and secured with nails, string or wire.

The root ball of a balled-and-burlapped tree is durable, but take care to avoid breaking or crushing roots in transport and handling.

CONTAINER-GROWN TREES Container-grown trees have smaller root balls and many times more fine roots than similarly sized field-grown trees. Container-grown trees dry out more quickly, making them more sensitive to drought injury after planting.

Fabric containers or fabric bags are made of a heavy flexible fabric especially designed for this growing method. Trees are planted in the fabric containers that are then planted in the ground. While their smaller size makes them easier to handle, they are also more fragile and dry out faster than the root balls of balled-and-burlapped trees.

Trees and shrubs are most commonly grown in plastic containers that are placed either above ground or, more recently, below ground and inside permanently installed containers with specially designed drainage holes. This latter method, known as pot-in-pot, insulates the root system and should produce roots that are more uniformly distributed than those found in above-ground containers.

Containers are usually filled with an artificial or soilless growing medium composed of one or more materials like bark, peat moss, compost and sand. These media are generally coarser than soil, which permits them to drain quickly and which, in turn, helps prevent root rot.

CHECKING THE ROOT BALL FOR DEFECTS The health of a plant's root ball is critical to its ultimate survival. Some root ball defects are obvious, while others require careful observation and inspection to discover. A thorough inspection before planting will help prevent future disappointment. One defect can be easily diagnosed without removing soil or the growing medium from the root ball.

Check the main roots close to the tree's trunk. Look for kinked or circling roots close to the trunk and near the soil surface. If circling roots are tight up against the trunk, do not purchase the tree. Circling or kinked roots less than about one-third the trunk diameter can be cut at the point where they begin to circle.

Once the tree is out of the container, the root ball should stay together but be somewhat flexible. You should be able to pick the root ball up and gently place it back in the container without losing much media. If the root ball falls apart when you remove it, particularly with shrubs, it may have just been "stepped up" to a larger container.

If many roots circle around the outside of the root ball or the root ball is very hard, it is said to be pot-bound or root-bound. A mass of circling roots on the outside of a root ball can act as a physical barrier to root penetration into the landscape soil after planting. The circling roots can also choke and kill the tree as it grows older.

Do not purchase pot-bound plants. Examine the roots on the surface of the root ball. Do not buy a plant with black roots. These roots were probably killed by heat stress, freezing temperatures or over-watering. With trees and shrubs that are balled-and-burlapped, note whether the root ball has been secured tightly with pins, twine or wire.

A loose or droopy root ball indicates that the plant was not properly cared for and may perform poorly after planting. The trunk should be sturdy in the root ball. If the trunk is unstable or needs a stake to prevent it from falling over, the root system may be inferior.