Choosing a tree to plant: what ISA and the Arboricultural Association tell owners

This page reports what the official source says. It is not legal advice: ask the office named here. It does not say which tree suits any garden. The ISA utility brochure sends owners with further questions to a local ISA Certified Arborist, utility company, local nursery or county extension office, and the Arboricultural Association names an AA Registered Consultant as one person to ask.

The questions ISA asks before the species

The ISA owner page Choosing the Right Tree says tree selection and placement are important decisions for a homeowner, and that matching the tree to the site benefits both. It says an owner should first weigh the soil, how much room sidewalks or driveways need and what job the tree is for, and only then ask what kind of tree to plant. The ISA brochure Tree Selection and Placement opens with the same questions and adds how maintenance will be provided and how large the tree will be when full grown.

Factor	What the ISA brochure says
Function	ISA lists what a tree is for: leaf-dropping shade trees for summer cooling with winter sun, evergreens for wind or screening, and fruiting plants as food for people or wildlife.
Form and size	ISA says a well-matched shape can lower upkeep and add value, and that a tree's grown size decides how much it gives back, with bigger trees usually returning the most.
Soil	ISA says soil in crowded urban areas and new housing developments is often disturbed, thin, packed down and dry, and that an arborist can sample it for testing.
Sun and wind	ISA names sunlight as a factor in the choice of tree or shrub, and wind exposure as another.
Space	ISA lists utilities above and below ground, paving, buildings, sight lines and neighbouring trees as limits, and says a tree needs room overhead and underground.
Hardiness	ISA describes hardiness as whether the tree can survive the temperature extremes of the region.
Drainage	ISA says roots need oxygen to develop, that poor drainage limits the oxygen available, and that this may kill the tree.
Pests and disease	ISA says each plant has its own pests and diseases, and that how serious they are differs from place to place.

The brochure also states that the top five causes of tree death come from things people do: soil compaction, under-watering, overwatering, vandalism and, as the number-one cause, planting the wrong tree. It says these together account for more deaths than all insect and disease deaths combined.

What ISA says about the tree in the nursery

The ISA brochure Buying High-Quality Trees describes what it calls a high-quality tree: a straight trunk with well-spaced branches, a trunk free of wounds or damage and roots growing straight out from the trunk. A low-quality tree, it says, has several stems from one point with branches growing into each other, wounds from handling or incorrect pruning, or roots that are limited, crushed or circling in a ball or container that is too small. It says these problems can greatly reduce the tree's prospects.

The brochure goes through the three ways nursery trees are sold.

Bare root: no soil around the roots, usually small trees. The brochure says the roots should not be crushed, torn, dried out or discolored.
Balled and burlapped: field-grown roots held in soil with burlap and wire or rope. The brochure says the trunk flare should be visible at the top of the ball and gives a ball diameter of at least 10 to 12 times the trunk diameter, measured 6 inches (15 cm) above the flare.
Container: roots and soil in a pot. The brochure says roots should not twist or circle, and that circling roots may girdle and kill other roots or the whole tree.

On form, the brochure says branches seen on a young shade tree may not be there at maturity, because lower ones are shaded out or pruned away. It says narrow branch angles and several branches at one point on the trunk raise the chance of weak attachments and cracks. The guides on planting depth and root flare and planting and soil standards by country report what other sources say after purchase.

Trees and utility lines

The ISA brochure Avoiding Tree and Utility Conflicts divides the ground around distribution lines into three zones. The table gives its figures.

Zone	Distance from distribution lines	Mature height the brochure gives
Low	15 feet (4.5 m) either side of the wires	20 feet (6 m) or lower
Medium	Between 15 and 50 feet (4.5 and 15 m)	40 feet (12 m) or lower
Tall	At least 50 feet (15 m)	Any, including large species

The same brochure says natural gas operators often keep the area directly over a pipeline and 10 feet (3 m) each side clear of trees. It says older cement, clay or cast-iron water and sewer pipes that have degraded may leak, and that moisture from a leak attracts roots which can penetrate and widen cracks. For work near power lines, the guide on trees touching power lines reports who handles it, and the guide on call before you dig lists the locating services.

The Arboricultural Association view

The Arboricultural Association page Managing your Trees says planting a tree needs forethought and planning, with the surrounding landscape and buildings, the space available, the soil type and the site all weighed. It says careful thought helps an appropriate species be chosen. It names an Arboricultural Association Registered Consultant as one person to ask. It adds that trees close to buildings can cause nuisance, and that some trees are protected by tree preservation orders or conservation areas. The guide on tree protection laws lists who handles permits.

Who to call

ISA Find an Arborist: the ISA directory, which its brochures point owners to for help with tree selection
Arboricultural Association, find a professional: the directories of ARB Approved Contractors and AA Registered Consultants
Locating services before digging: the services that mark buried utilities in each country
Tree protection offices: the offices that handle permits for protected trees