The terms that decide what tree work in Ottawa costs and whether it needs a permit, in plain language. DBH is the trunk diameter at about 1.4 m off the ground; 30 cm of DBH (a tape reading of roughly 95 cm around) makes a private tree inside Ottawa’s urban boundary a distinctive tree that needs a City permit under By-law 2020-340. The root flare is where a stump is measured for a quote, never the cut face. Included bark is the hidden weakness in a tight V-shaped fork. A hanger is a broken limb caught in the canopy and the most urgent thing on a property after a storm. Topping is not pruning. Blonding on an ash means emerald ash borer. Every definition below links to the guide it comes from, and every number is on our pricing page or our by-law page.
Measuring a tree and the permit rule
DBH (diameter at breast height)
The width of the trunk measured at roughly 1.4 m off the ground, not at the base where the flare makes it look bigger. It is the number the City of Ottawa’s tree by-law turns on. Thirty centimetres of diameter is about 94 cm of circumference, so if a tape around the trunk at chest height reads more than about 95 cm, assume the tree is over the line. From the permit guide.
Distinctive tree
Under Ottawa’s Tree Protection By-law 2020-340, a private tree 30 cm or more in DBH on a lot of one hectare or less inside the urban boundary. It needs a distinctive tree permit before it comes down. Since February 1, 2024 the suburban threshold has been the same 30 cm as the inner city (it was 50 cm before, and many older web pages still say so). The fee is $174 per tree standard, $870 per tree for infill development; fines run from $500 to $100,000 and land on the property owner, not the contractor. Dead trees, immediate hazards and private ash infested with emerald ash borer are exempt, but photograph the tree before anyone cuts. From the by-law page.
Urban boundary
The line the by-law draws, taken from the City’s Official Plan. Inside it (Kanata, Stittsville, Barrhaven, Nepean, Orléans, Gloucester, Riverside South, Findlay Creek and the whole inner city) the 30 cm rule applies. In the rural villages (Manotick, Greely, Osgoode, Metcalfe, Richmond, Carp, North Gower, Navan, Cumberland village, Constance Bay and the rest) private trees are not regulated by 2020-340 unless a Planning Act application is on the property. Properties over one hectare and any lot under a Planning Act application are caught at 10 cm. City-owned trees are protected everywhere. Check the address on geoOttawa when near a boundary. From the by-law page.
Root flare
The point at ground level where the trunk widens out into the roots. Two reasons it matters. For a stump quote, the diameter is measured across the root flare at ground level, never across the cut face on top, which is always smaller. For a living tree, a root flare buried under soil or mulch is one of the commonest causes of a single tree turning colour or dropping leaves early; check it with a trowel. From the pricing page and the early leaf drop guide.
Caliper
The trunk-diameter measure nurseries use for young trees. A one-inch caliper tree takes 12 to 18 months to establish its root system and a four-inch caliper tree four to six years (Colorado State University Extension), which is why a tree planted this spring goes into its first Ottawa winter on a root system not much bigger than the pot it came in. From the new-tree winter care guide.
Structure and risk
Included bark
Bark trapped inside the join where two stems grow tight against each other, in place of the wood that should connect them. The tree looks like it has a solid fork; it has two stems leaning on a seam. It is the single most useful thing to learn to spot in a twin-stemmed maple. From the cabling and bracing guide.
Codominant stems and the V-shaped union
Two stems of similar size rising from the same point, usually in a tight V. Weak branch junctures showing included bark are among the predictors of storm failure named in the research quoted in our wet snow guide, alongside decayed or dead branches, unbalanced crowns and shallow rooting.
Cabling and bracing
A steel or synthetic support installed high in the crown between two stems. A cable limits how far the stems can pull apart; it does not make a tree safe, and it commits the owner to an inspection cycle: a ground check every year, a climbing inspection about every three years and replacement after seven to ten years. From the cabling and bracing guide.
Hanger (hung-up limb)
A broken branch caught in the canopy above the ground. Hangers come down without warning and in no predictable direction, and they are the classic cause of injury in the days after a storm, which is why a hanger is same-day work while a tree fully down and touching nothing can wait a few days at the regular rate. From the emergency tree removal page.
Root plate
The disc of roots and soil that anchors the tree. Most tree roots sit in the top 15 to 60 cm of soil, so the plate is wide and shallow. A partly failed root plate shows as soil heaving or cracking on the side opposite the lean, and it can finish failing in the next gust; that is an urgent call. After grinding, the stump is gone but the root plate is left in the ground to break down. From the emergency page, the tree roots guide and the emerald ash borer guide.
Settled lean versus failing lean
A lean the tree has carried for years with no movement in the ground is a settled lean. A new lean, or any lean with heaving soil, a fresh crack in the lawn, or a gap opening between trunk and soil, is a failing one. The evidence is in the ground, not the trunk. Two things we would not do to a leaning tree: cable it to the house, or top it. From the leaning tree guide.
Topping versus crown reduction
Topping is cutting a crown back to stubs. It triggers a flush of weakly attached regrowth, and within a few years the tree carries the same sail on worse attachments, so it fails harder in the next storm. A crown reduction or thinning lowers wind load by taking selected branches back to a properly sized side branch. We do not top trees. From the leaning tree guide and the maple leaf spots guide.
Cleaning, thinning, raising and structural pruning
The four standard pruning operations: cleaning removes dead, dying and broken wood; thinning removes selected live branches to reduce density and wind load; raising removes lower limbs for clearance; structural pruning shapes a young tree’s framework so it never needs the other three as badly. Dead wood and hangers come out in any month. Shaping and thinning of a healthy tree belongs in December to March, February into March best; September is the poorest month for it. From our pruning service page and the tree care calendar.
Closed pruning windows (elm and oak)
Elms cannot be pruned in Canada from April 1 to September 30 under the Canadian Food Inspection Agency’s Dutch elm disease guidance, because the beetles that carry the fungus are drawn to fresh cuts. Oaks should not be cut from April through November as an oak wilt precaution. Storm damage on either is dealt with when it happens. From the pruning guide and the calendar.
How the job is done and priced
Rigging
Taking a tree down in pieces from the top, each piece tied off and lowered under control so nothing lands on the house, the fence or the garden. Rigging needs sound wood that will hold a load. Decayed or long-dead wood cannot be trusted with it; once an ash has stood dead for two or three winters it is usually too brittle to climb, which forces a bucket truck or crane, billed at cost. That is why a dead tree usually costs more to remove than a living one. From the cost guide and the pricing page.
Drop zone and complexity factor
The drop zone is the clear ground a climber can lower or drop wood into. An open drop zone with sound wood and nothing underneath is the cheapest tree there is; a tree behind a narrow gate, over a roof, or with wires beneath it is the same tree at a very different price. On day-rate work the quote states a complexity factor from 1.0 (open drop zone, sound wood, no targets) to 2.0 (crane, bucket or engineered dismantle required), so the number is agreed before the day rather than argued after it. From the cost guide and the pricing page.
Stump grinding
Grinding a stump into chips below ground level, to a standard depth of 20 to 30 cm below grade, deep enough to seed, sod or plant over. It is priced by diameter at the root flare, never by the hour, because grinding volume rises with the square of the diameter: $250 for a stump up to 30 cm, $310 at 40 cm, $390 at 50 cm, $490 at 60 cm, $610 at 70 cm, $760 at 80 cm, $950 at 90 cm and $1,190 at 100 cm, plus HST. Hardwood stumps (oak, maple, elm, ash) run about 20% more; additional stumps on the same visit are half the schedule; grindings are left on site as backfill unless haul-away is requested (+$150). Stumps are quoted from a photo, often the same day. From the pricing page and the stump grinding page.
Minimum charge
$160 plus HST, one minimum on any job. It is not a call-out fee added on top of the work; it is the least any job costs. Quotes are free. From the pricing page.
Emergency or storm callout
Emergency, after-hours and storm work is billed at 1.5 times the published schedule, so a removal normally quoted at $1,000 is about $1,500 as an emergency callout. The phone is answered 8 AM to 9 PM seven days a week; we do not claim 24/7. Anything touching a hydro line is a 9-1-1 and Hydro Ottawa call first, and everyone stays 10 m back until the line is dealt with. From the emergency page.
Commercial general liability (CGL) certificate
The insurance document to ask for before anyone climbs. Because no licence is required to run a tree company in Ontario, this certificate and a written quote are the two pieces of paper that actually separate companies. Have it emailed by the company’s broker (not a photo from a phone), check that the named insured matches the quote, that the dates cover the job, and that climbing and removal are not excluded. We provide ours on request. From the how to choose a tree service page.
TRAQ (Tree Risk Assessment Qualified)
A qualification in assessing the likelihood that a tree, or part of one, will fail and what it would hit if it did. It is what lets an assessor give an informed answer to “does this tree have to come down?” rather than a guess. Max holds it. From the About page.
Direct agreement (the door-to-door contract)
A contract signed at your own door is a direct agreement under Ontario’s Consumer Protection Act, and you can cancel it within 10 days of receiving the written copy. Worth knowing in the week after a storm, when crews with verbal quotes and no insurance that covers climbing knock on doors. From the how to choose a tree service page.
Pests and disease you will hear named
Emerald ash borer (EAB) and its signs
The beetle that has killed most of Ottawa’s untreated ash. It works under the bark and kills from the top down. The signs, in the order people notice them: crown dieback starting at the top, epicormic shoots (sudden leafy growth low on the trunk), woodpecker blonding, vertical bark splits with S-shaped galleries underneath, and D-shaped exit holes 3.5 to 4 mm across. By the time dieback is obvious from the driveway the tree has usually been infested for two to three years. From the emerald ash borer guide.
Blonding
Pale patches on the trunk and larger limbs of an ash where woodpeckers have stripped the outer bark to reach emerald ash borer larvae underneath. It is a reliable indicator, and in winter it is often the most visible sign on an Ottawa street. From the emerald ash borer guide.
EAB regulated area
The list of counties, districts and municipalities where the Canadian Food Inspection Agency restricts the movement of ash material and firewood because emerald ash borer is established. Ottawa is inside it, urban and rural, and so is most of eastern and central Ontario: Lanark, Renfrew, Frontenac, Leeds and Grenville, Prescott and Russell, the Kawarthas and Muskoka among others. Every rule in the directive is written as a restriction on moving wood out of a regulated area, so a trip that starts and ends inside it is not restricted. The boundary is a written list, not the province or the city limit, and it is worth reading the entry for your destination. From the firewood guide.
Movement certificate
The CFIA document required before regulated ash material (trees whole or in parts, logs, branches, bark, chips, nursery stock, firewood) can leave a regulated area. Moving ash firewood out without one is prohibited whether the purpose is commercial or private, and the directive names cottage and camping trips specifically. Non-ash firewood can only be moved out by a facility approved under the CFIA programme; there is no homeowner version of that permission. The prohibition runs all year. From the firewood guide.
Movement Prohibition Notice
A notice the CFIA can issue for a specific property once emerald ash borer is confirmed there. It stops the affected ash material leaving that address at all, including a few rounds for a neighbour. Ash from your own property can still be burned on your own property, since nothing is leaving the regulated area. From the firewood guide.
Spotted lanternfly regulated area
The area the Canadian Food Inspection Agency put in place on 23 October 2026 after confirming Canada’s first established spotted lanternfly population: Essex County, the city of Windsor, the township of Pelee and the municipality of Chatham-Kent (Chatham-Kent as a buffer next to the established population, not because a population was confirmed there). Anything moving out of it into the rest of the country has to be free of every life stage of the insect first; the CFIA names nursery stock, outdoor household items, ornamental stones and firewood and says the list is not limited to those. Ottawa is not in it, and Ottawa’s only record is still one dead insect intercepted in January 2023. A different thing from the emerald ash borer regulated area above, which Ottawa is inside. From the 26 October lanternfly update.
Established population (CFIA pest status)
The top of the CFIA’s four-step scale for an invasive insect: a breeding population confirmed by survey, as opposed to an interception (a specimen confirmed but not found on a survey, such as one that arrived on a vehicle), a report, or a detection (a live insect confirmed in the environment by an official survey). Windsor went from detection on 15 September 2026 to established on 23 October 2026 after hundreds of confirmed observations across Essex County. Ottawa’s spotted lanternfly line is an interception, which is the bottom of that scale. From the 26 October lanternfly update and the 25 September guide.
Mechanical girdling (mower and trimmer damage)
Bark killed at the base of the trunk by a mower deck or a string-trimmer line, almost always at the root flare where the machine meets the turf. On a young maple or birch the bark protecting the tree’s water and food supply is about 1.5 mm thick, so one pass goes through it; a mature rough-barked oak never notices the same bump. The wound is irreversible at any size, repeat hits on the same side add up to worse than one large wound, and dead bark all the way round the base is fatal. Decay fungi enter the cut and enlarge it, so the crown often shows nothing for three or four years. Pull the grass back to bare bark and look for nicks at one consistent height on the mower side. From the mower damage guide.
Mulch ring
A circle of mulch that takes the grass, and therefore the mower, away from the trunk. K-State Research and Extension gives the size: at least three feet of ring diameter for every inch of trunk caliper on a young tree (a two-inch sapling wants a six-foot circle), with 4 to 6 inches of bare ground between the bark and the start of the mulch: a flat donut, never a volcano piled against the trunk. On a mature tree the formula stops mattering; the ring only has to be wide enough that the turf edge never reaches the bark. Cut the sod out rather than burying it, taking only the top few inches. From the mower damage guide and the winter care guide.
Tar spot
Raised, glossy black blotches on Norway and Manitoba maple leaves, from a pencil dot to the size of a loonie, often with a yellow halo: the fungus Rhytisma acerinum. It looks worse than it is and does not kill the tree. It infects new leaves in wet spring weather, so a treatment offered in August cannot work; fungicides are preventive and go on at bud break. Rake and remove the fallen leaves, because the fungus overwinters in them. From the maple leaf spots guide.
Anthracnose
Irregular brown blotches that follow the leaf veins, often starting at the edge and working in, with the leaf curling. It is the one that causes early leaf drop on maples in a wet year, and like tar spot it overwinters in the leaf litter. From the maple leaf spots guide.
Armillaria (honey fungus)
Tight clusters of honey-coloured mushrooms at the base of a trunk, usually in fall. Unlike leaf spots, this is a root rot that is actively killing roots and the base of the trunk, and by the time the crown shows it much of the damage is done. Worth a photo to us. From the mushrooms guide and the calendar.
Girdling root
A root that has grown around the trunk instead of away from it and is slowly strangling the tree. It is one of the usual answers when one tree in a yard turns colour or drops leaves in September while the same species on the street stay green. Excavate the root flare to find it; do not cut a root over about 5 cm without advice. From the early leaf drop guide.
Sunscald
Winter bark injury on a young tree: the sun heats the trunk by day, it freezes fast at night, and the bark cracks. A plastic tree guard around the lower trunk handles sunscald and rabbits at once if it reaches about two feet above the expected snow line; take it off in late spring. From the new-tree winter care guide.
Quick answers
What does DBH mean and how do I measure it?
Diameter at breast height: the trunk width at roughly 1.4 m off the ground. Wrap a tape around the trunk at chest height; a reading of about 95 cm around equals 30 cm of diameter, which is Ottawa’s permit threshold inside the urban boundary.
What is a distinctive tree in Ottawa?
A private tree 30 cm or more in diameter at breast height on a lot of one hectare or less inside Ottawa’s urban boundary. It needs a permit under Tree Protection By-law 2020-340 before removal ($174 per tree; fines $500 to $100,000). Dead trees, immediate hazards and ash infested with emerald ash borer are exempt.
Where do I measure a stump for a grinding quote?
Across the root flare at ground level, the widest point where the trunk meets the roots, not across the cut face on top. Prices run from $250 for a stump up to 30 cm to $1,190 at 100 cm, plus HST; hardwoods about 20% more.
What is included bark and why does it matter?
Bark trapped in the join between two stems where connecting wood should be. It makes a tight V-shaped fork far weaker than it looks and is one of the main predictors of a stem splitting out in a storm or under wet snow. A cable can limit how far the stems move apart but does not make the tree safe.
What is the difference between topping and crown reduction?
Topping cuts the crown back to stubs and produces weakly attached regrowth that fails harder in the next storm. A crown reduction takes selected branches back to a properly sized side branch, lowering wind load without wrecking the tree. Max Trees does not top trees.
What is blonding on an ash tree?
Pale patches where woodpeckers have stripped the outer bark to reach emerald ash borer larvae. It is a reliable sign of infestation and is easiest to see in winter. Look also for D-shaped exit holes 3.5 to 4 mm across and S-shaped galleries under split bark.
Related: our published prices · permit rules by neighbourhood · the Ottawa tree care calendar · how to choose a tree service in Ottawa · emergency tree removal. Questions about a tree you are looking at: 613-715-0103, or send a photo through the contact page.
Before the snow, look at the bottom of your own trunks: mower and string-trimmer damage at the root flare is the wound that shows up in the crown three or four years later. On a young maple or birch the bark is about 1.5 mm thick, a trimmer takes it off in one pass, the damage is irreversible, and a wound all the way round the base is fatal. The fix is a mulch ring: at least three feet of ring for every inch of trunk caliper on a young tree, with 4 to 6 inches of bare ground between the bark and the mulch.