Branch collar – Pruning cuts should be made just outside the point where a branch is connected to a tree’s trunk.

Bark ridge – A ridge of bark often develops where the bark of a tree and the bark of a branch meet. The branch collar will be just outside this ridge.

Butt flare – A properly planted tree will show a pronounced flare at the point where the roots connect to the trunk. This butt flare should be visible above both ground and mulch. Trees that are delivered balled and burlapped from the nursery should be examined carefully, as the ball of soil often is packed higher up the trunk than the soil in which the tree was growing originally.

Canopy – The entire mass of branches, twigs and leaves of a tree. Proper pruning of the canopy lets in enough light that all parts of the tree receive adequate sunlight.

Drip line – The so-called drip line, an imaginary line around a tree at the outer circumference of branches, was once thought to be the extent of a tree’s roots. In fact, the circumference of the roots can be from one-and-a-half to two times the circumference of the tree’s canopy, depending on the age and type of tree.

Flush cuts – This is an old style of pruning, no longer done by responsible arborists. Flush cutting prevents the tree from compartmentalizing a wound, and can encourage decay and weakening of a tree.

Girdling root – Any of a number of impediments can cause a root to grow around the tree’s trunk rather than out from it. Since this root will prohibit the trunk’s natural growth, the root will eventually cut off the tree’s ability to transport water up from its roots and starches down from its branches.

Heading – Heading is similar to shearing (see below) and usually involves cutting a branch at a point where no new growth will conceal the cut. It is not recommended.

Integrated Pest Management (IPM) – IPM is a sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health, and environmental risks.

Mycorrhizal fungi – A symbiotic relationship exists between many trees’ roots and a specialized fungus known as mycorrhizal fungi. These fungi permit the roots to absorb nutrients more effectively and provide access to more nutrients than the roots could reach on their own. When soil nutrients are depleted or the soil is compacted, injecting fertilizer mixed with mycorrhizal fungi can benefit the tree and the soil.

Root zone – Most species of trees have up to 80% of their roots in the top 12 to 18 inches of soil. Trees are best planted in places where their roots can spread out freely; avoid installing weed barriers around the roots of trees, as this may cause roots to grow in a circle rather than straight out from the tree. The roots of a tree need oxygen, so it’s important not to change the depth of the roots by adding or removing soil from around the root zone.

Shearing – Some evergreen trees and shrubs can be sheared to provide a formal-looking hedge. Boxwood and privet can provide a long-lived, dense screen for a boundary line when sheared properly. Hemlocks often create a better appearance if left unsheared.

Soil compaction – The ideal soil for a tree is what you would find in a forest: light, humus-rich soil with adequate drainage and plenty of nutrients. The typical American lawn, unfortunately, is depleted of nutrients by having the topsoil removed during construction. Broad spectrum insecticides kill off many beneficial insects and earthworms. Over time, many lawns become as impervious to rain as concrete. When this happens, soil is described as compacted, and tree roots have difficulty growing and locating water and nutrients. Anything that promotes rejuvenation of soil is beneficial to trees: earthworms, organic mulch, deep watering during droughts, and soil aeration.

Tap root – Different species of trees grow different types of roots. In most trees, however, a deep tap root, if it exists at all, will cease to be important as the tree ages. The bulk of a tree’s nutrition will come from its many small feeder roots, while stability is achieved through large buttress roots.

Thinning – Thinning of outer and upper branches on a tree or shrub often improves the overall health of the tree by letting in more air and light, thus reducing the chances of fungal disease. Lower branches, given more light, will grow better and be more resistant to insects and disease.

Topping – Customers sometimes request that we reduce the height of a tree by topping. We do not recommend this procedure, as it is generally harmful to the tree’s health. It is also likely to result in new, unnatural growth in the same area. Whenever possible, we prefer to shape the tree in the direction of its natural growth habit.

Water sprouts – New vertical shoots that grow along the top of a branch are called water sprouts, and are indicators of stress on the tree. Never remove all of the water sprouts – the tree has grown these in an attempt to provide more food for itself. Water sprouts are a signal to call in an arborist to diagnose the problem.