Tree Care: When to Hire a Certified Arborist

Healthy trees shade a home, frame a yard and add value. Neglected or badly pruned trees can drop limbs on roofs, cars and people. This guide explains which tree jobs are safe to handle yourself, which belong to a professional, and how to choose one, using brochures from the International Society of Arboriculture (ISA) on its consumer site TreesAreGood.org.

Which tree jobs can you do yourself?

Small jobs you can reach from the ground with hand tools are usually homeowner work: pruning small branches on young trees, removing suckers, watering new trees and spreading mulch (keep it off the trunk). Anything that needs a chain saw overhead, a ladder in the tree, or ropes is a job for a professional.

When should you hire an arborist?

ISA lists pruning to remove limbs that:

• interfere with utilities or structures,
• obstruct streets or sidewalks,
• are dead, storm-damaged, weak or decayed and pose unacceptable risk,
• are diseased or insect-infested.

ISA recommends an arborist to help decide on removal when a tree is dead or dying, considered an unacceptable risk, causing an obstruction that pruning can’t correct, crowding more desirable trees, or in the way of new construction. Arborists also provide plant health care, cabling and bracing for weak branches, soil aeration, lightning protection, tree risk assessment and tree protection during construction. After a storm, ISA notes that removing or pruning damaged trees can be dangerous, and an arborist can do it safely.

What does an ISA Certified Arborist credential mean?

ISA certification is voluntary and nongovernmental. ISA says ISA Certified Arborists and ISA Board Certified Master Arborists have passed comprehensive exams covering tree care, must continue their education to keep the credential, and must follow a code of ethics. TreesAreGood.org has a “Find an Arborist” tool to find credential holders near you and a “Verify a Credential” tool to confirm one.

How do you choose a tree service?

ISA’s checklist:

• Check for membership in professional organizations such as ISA, the Tree Care Industry Association (TCIA) or the American Society of Consulting Arborists (ASCA).
• Check for an ISA arborist credential.
• Ask for proof of insurance, and call the insurance company to confirm it.
• Check for any local permits and licenses required.
• Get more than one estimate and ask for references.
• Don’t automatically accept the lowest bid; compare credentials, the written work specifications and price.
• Be wary of people who go door to door offering bargains.
• Get it in writing, and read the contract before you sign.

Some cities require a permit to remove or heavily prune certain trees; ask your city or county. Our guide to hiring a contractor covers bids, contracts and payments.

Why shouldn’t you top a tree?

Topping cuts tree branches back to stubs or to small side branches. ISA calls it “perhaps the most harmful tree pruning practice known” and says it is not a viable way to reduce a tree’s height and may increase risk in the long term. ISA says topping can remove 50 to 100 percent of a tree’s leaf-bearing crown, which can starve the tree, trigger fast weak sprouts below each cut, open large wounds to insects and decay, and expose bark to sunburn. Other names for it include heading, tipping, hat-racking and rounding over. If a tree is too big for its spot, ask an arborist about proper crown reduction or replacement.

How do you plant trees around utilities?

ISA advises matching the tree’s mature height and spread to the space available, above and below ground. It notes that roots commonly spread many times the width of the crown and can extend farther than the tree is tall, and warns never to assume buried utilities are deeper than you plan to dig. Before you dig a planting hole, contact 811 a few business days ahead for free utility marking; see our 811 guide. Keep tall-growing trees away from overhead lines.

How do you care for young trees?

Water new trees through their first seasons, especially in dry spells, mulch the root area while keeping mulch off the trunk, and prune young trees early to build good structure. Your lawn watering schedule may not be enough for a new tree; see our lawn watering guide and ask your local extension office or utility how often to water trees and shrubs.

Tree checks are part of our spring and fall home maintenance checklist.