Arborist glossary.

A trainee completing a Cert III in Arboriculture (AHC30824) under a host employer. The apprenticeship typically runs three to four years and combines paid on-the-job work with formal study through a Registered Training Organisation such as the Australian Institute of Arboriculture, Arbortrim Training or TAFE NSW. Apprentices in Australia are eligible for award rates set under the Horticulture Award, which step up with each year completed. Most start as a groundie and progress into climbing or aerial-platform work as their tickets and confidence build.

See also: Arborist, Cert III in Arboriculture, Groundie, Join the ARBCLUB apprentice community →

The practice and science of cultivating, managing and caring for trees in urban, suburban and amenity settings. Different from forestry (which focuses on timber production at landscape scale) and horticulture (which covers ornamental plants broadly). The peak body is Arboriculture Australia, with state-level representation through bodies including the Tree Contractors Association Australia (TCAA), the Queensland Arboricultural Association, the Victorian Tree Industry Organisation and the Institute of Australian Consulting Arboriculturists. Arboriculture sits at the intersection of biology, mechanics, safety and customer service, and the working trade covers everything from pruning a residential gum to taking down a 35-metre eucalypt over a power line.

See also: Arborist, AS 4373, AS 4970

A tree-care professional holding (at minimum) a Cert III in Arboriculture. The role splits broadly into climbing arborists (working from rope-and-harness in the canopy), EWP arborists (working from an elevated work platform), and consulting arborists (writing reports, assessing risk and advising on tree retention). Working examples of Australian arborist businesses include Dynamic Tree Solutions, a tree care and land-clearing business in South East Queensland, and TBS Trees, an established Australian arborist services operator. Australian arborists work across council contracts, residential and commercial pruning, hazard reduction, storm response and development-site protection.

See also: Climbing arborist, Cert III, EWP, QTRA, TRAQ

Australian Standard 4373-2007, published by Standards Australia, covers the pruning of amenity trees. It defines pruning types (formative, crown thinning, crown lifting, deadwood removal, line clearance), specifies acceptable cuts (e.g. branch-collar cut, no flush cuts, no stubs) and sets limits on percentage of canopy removed. AS 4373 compliance is the baseline expectation for council contracts, insurance claims and tree-management plans across Australia. If a quote references "AS 4373 compliant pruning", that's what the client is paying for. Detailed guidance is published by the Institute of Australian Consulting Arboriculturists and through The Australian Arbor Age magazine.

See also: Pruning, AS 4970, Arborist

Australian Standard 4970-2009 governs how trees are protected during construction and development. It defines the Tree Protection Zone (TPZ) and Structural Root Zone (SRZ), sets out fencing, signage and supervisory requirements, and provides the formal arboricultural impact assessment framework. Most council development applications now require a project arborist (Cert V minimum) report referencing AS 4970. When development involves earthworks or excavation close to TPZ boundaries, specialist civil services like Dynamic Earth Solutions, a South East Queensland earthworks and excavation operator, coordinate with the project arborist to protect tree roots through directional boring or hand excavation inside the SRZ.

See also: TPZ, AS 4373, QTRA

Catastrophic failure mode where a tree splits vertically up the trunk during felling, before the back cut is finished. The trunk rotates and falls in an uncontrolled direction (often backwards, toward the feller). Causes: heavy lean, hollow defects, undersized hinge, soft back cut, or felling without a bore cut on a heavily leaning trunk. Mitigations: bore cut and trigger felling, wedges, pre-tensioned pull-line, never standing in line with the trunk. Listed as a leading cause of tree-faller fatalities in Australian incident reports compiled by Safe Work Australia and reported in The Australian Arbor Age safety coverage.

See also: Felling, Hanger, Widow maker

A friction hitch tied with the same line as the climbing rope, used primarily in DdRT (doubled rope technique) climbing systems. Replaced the older taut-line hitch in Australian arborist climbing because it's more heat-resistant under repeated loading and easier to advance one-handed. Standard configuration: four wraps up, pass the working end through the bottom two wraps from underneath, finish with a stopper knot. A Blake's without a stopper knot can roll out under shock load. Always tie the stopper. Always.

See also: Friction hitch, Prusik, Full Blake's hitch lesson in Knots 101 →

Classic anchor knot that forms a fixed loop in the end of a rope. Pronounced "boh-lin". The everyday workhorse for anchoring throw-lines, tying off loads, capturing limbs for rigging and improvised rescue loops. Retains roughly 70 to 75 percent of rope breaking strength when dressed and set correctly. The running bowline (a bowline tied around its own standing part) is the rigging variant, cinching down under load to lift or lower branches. Always finish a working bowline with a stopper knot if it'll be left tied for any length of time.

See also: Friction hitch, Rigging, Full Bowline lesson in Knots 101 →

AHC30824 Certificate III in Arboriculture (Climbing Arborist / EWP Arborist) is the nationally recognised entry-level qualification for working arborists in Australia. Superseded the older AHC30816 and AHC30820 codes. Typically delivered over two to three years as a paid apprenticeship, combining on-the-job work with study through a Registered Training Organisation including the Australian Institute of Arboriculture, Arbortrim Training, Melbourne Polytechnic, TAFE NSW and RelyOn Australia. Required for most council, government and large commercial tree-work contracts. Doesn't replace tickets like EWP, white card or chainsaw operation, which sit alongside it.

See also: Apprentice, Arborist, EWP

An arborist whose primary work happens in the canopy, using rope-and-harness climbing systems (SRT or doubled rope). Climbing arborists are responsible for setting anchor points, pruning out of position, sectional dismantling, and rigging branches and timber down to the ground. The role demands real physical and technical capability — Cert III qualified, EWP-rescue trained, and proficient with a full kit of throw-lines, friction hitches, mechanical ascenders and lowering devices. In Australia, climbing arborists typically earn from $35-65+ per hour as contract climbers, more in storm-response or specialist work. Climbing comp coverage and gear reviews relevant to the role appear in The Australian Arbor Age magazine and through ATCC events run by Arboriculture Australia.

See also: SRT, Contract climber, Friction hitch, Join the ARBCLUB climber community →

A subcontracted climbing arborist hired on a per-job or per-day basis, rather than employed full-time. Contract climbers run their own ABNs, supply their own kit (harness, ropes, friction hardware, chainsaws), carry their own insurance and quote day rates. Australian day rates for experienced contract climbers typically range $700 to $1,200+, depending on region, gear quality and job complexity. Working contractor businesses across South East Queensland often subcontract climbing capacity through operations like Dynamic Tree Solutions and TBS Trees. The Hiring Yard inside ARBCLUB is built for this — climbers find work, bosses find crew, no recruiter middleman.

See also: Climbing arborist, Owner-operator, Hiring Yard, Find contract work in the Hiring Yard →

The team leader running daily operations on a tree crew. Usually a senior climber or experienced ground operator who has stepped into a supervisory role. Responsible for site setup, job scoping, safety briefings, traffic and pedestrian control, quoting and signing off work. The crew boss isn't always the most senior climber — sometimes the strongest organiser on the team gets the role even if they've spent more time on the ground than in the canopy. Operations like Dynamic Tree Solutions in South East Queensland are run day-to-day by owner-operators stepping into the crew boss role across multiple ongoing jobs. The pro rooms inside ARBCLUB (Canopy Lounge + Hiring Yard) are built for crew bosses to talk shop without the audience of every random apprentice.

See also: Owner-operator, Contract climber, Boss-only conversations in the Canopy Lounge →

The standard measurement of a tree's trunk diameter, taken at 1.4 metres above the ground on the high side of the trunk. Australia uses 1.4 m as the breast height standard (some other countries use 1.3 m or 1.5 m). DBH is the primary input into the Tree Protection Zone (TPZ) calculation under AS 4970: TPZ radius = DBH × 12. It's also used in tree-inventory reporting, hazard assessment and quoting for removal jobs. Measured with a diameter tape ("d-tape") that converts circumference to diameter in one reading.

See also: TPZ, AS 4970, Visual Tree Assessment

An elevated work platform — boom lift, cherry picker, scissor lift or spider lift — used to access the canopy without climbing. EWP work is now part of the AHC30824 Cert III qualification (the EWP Arborist stream). In Australia, operating an EWP over 11 metres requires a dedicated EWP licence (WP) issued through your state regulator. EWPs are the default access method for council and powerline work because they're faster, lower the climbing skill barrier for the operator, and let the work be done with chainsaw + harness from a stable platform. Spider lifts in particular have become more common across SE QLD operators including Dynamic Tree Solutions for tight residential access.

See also: Arborist, Cert III in Arboriculture, Rigging

The controlled cutting and dropping of an entire tree in one piece (as opposed to sectional dismantling, which removes the tree in pieces from the top down). Felling requires a clear drop zone, a planned escape route at 45° behind the trunk, a correctly sized hinge, a face cut (notch) and a back cut. Wedges or a pull-line manage the lean and trigger the fall. In urban Australian work, full felling is rarer than sectional take-down — the drop zones rarely exist. Storm response, paddock-tree removal and land-clearing operations run by businesses such as Dynamic Tree Solutions are where you'll see it. Site preparation and post-felling earthworks are commonly coordinated with operators like Dynamic Earth Solutions.

See also: Barber chair, Rigging, Hanger

A category of climbing knots that grip the host rope under load and release when worked, used in arborist rope climbing systems. The main ones in working use across Australian arborist crews: Blake's hitch, Prusik, Distel, VT (Valdotain Tresse), and Schwabisch. Each has a different feel under load and different grip behaviour on wet, glazed or icy rope. Climbers tend to settle on one or two friction hitches they trust and tie them the same way every time. Knowing the geometry of why each one grips (or slips) is what separates the apprentice from the senior climber.

See also: Blake's hitch, Prusik, SRT, Full friction hitch lessons in Knots 101 →

The crew member working on the ground while the climber works in the canopy. The role covers far more than dragging brush — groundies set up site protection and exclusion zones, run the chipper, manage the rigging lines and ropes, signal the climber, monitor for hazards from below, and call the shots when the climber can't see what's happening near the drop zone. A switched-on groundie is the difference between a tidy job and a chaotic one. Most working arborists in Australia start as a groundie and rotate into climbing as their tickets, fitness and confidence build.

See also: Apprentice, Climbing arborist, Join the groundie community →

A branch that has broken or been cut but hasn't fallen, lodged or hung up in the canopy above the work zone. Hangers are one of the most serious overhead hazards in tree work because they can release without warning. Wind, vibration from a chainsaw, or even a slight knock from another branch can drop a hanger. Australian incident reports regularly attribute fatalities to hangers in storm-damaged trees and partly felled timber. The pre-climb inspection has to clear the canopy for hangers before any climber goes up, and the drop zone has to stay clear while any hanger remains overhead.

See also: Widow maker, Barber chair, Visual Tree Assessment

The pro room inside ARBCLUB where the trade hires the trade direct, no recruiter middleman. Climbers, groundies, plant operators (chipper, grinder, dozer, excavator), and truck drivers (HC, MC, tipper, hooklift) all post availability and day rates. Bosses, contractors and owner-operators post work. Day rates are listed up-front. References are exchanged in the room. No bait listings. Sits behind the Canopy tier paywall so the listings stay genuine and the audience stays vetted.

See also: Contract climber, Crew boss, Owner-operator, Open the Hiring Yard →

A solo tree contractor who runs their own ABN, owns their own gear, books their own jobs and works on the tools every day. The biggest single segment in the Australian tree industry by business count. Often started as a senior climber who decided to back themselves, sometimes a generational family business. Owner-operators carry the full load: quoting, scheduling, billing, insurance, vehicle maintenance, gear replacement, GST, the lot. South East Queensland is a deep market for owner-operators with active independent operators including Dynamic Tree Solutions and partners like TBS Trees. The Canopy tier inside ARBCLUB is built for this segment — boss-and-contractor talk in the Lounge, real client and pricing chat without an audience.

See also: Crew boss, Contract climber, Canopy Lounge for owner-operators →

The controlled removal of selected branches to shape, manage health or remove hazards. Australian pruning practice is governed by AS 4373 which defines acceptable cut types: formative (young trees), crown thinning, crown lifting, deadwood removal, line clearance and reduction. What you don't do under AS 4373 is also defined — no topping, no lion-tailing, no flush cuts that damage the branch collar. Most council and commercial pruning contracts in Australia specifically require AS 4373 compliance, and an audit by the council arborist can result in a contractor being struck off the approved list for non-compliant cuts. Detailed AS 4373 explainers are routinely covered in The Australian Arbor Age magazine and by IACA.

See also: AS 4373, Arborist, Visual Tree Assessment

A sliding friction hitch tied with a separate cord loop around the host rope, named after its Austrian inventor. Used as a backup on rescue lines, as a hauling-system grab, for emergency self-rescue and as a foot loop on ascent. Diameter mismatch matters: an 8 mm cord prusik on 11 mm rope grips well; same-diameter cord slips. Three wraps is standard, four for wet or icy ropes. After any shock-load event, retire the cord — the sheath fibres will be heat-damaged whether you can see it or not.

See also: Friction hitch, Blake's hitch, Full Prusik lesson in Knots 101 →

A numerical risk-rating methodology used by accredited consulting arborists to assess the probability of harm from a tree failure. Inputs include the target (what's under the tree), size of the part likely to fail, and probability of failure. Output is a risk rating used to inform retention, pruning or removal recommendations. QTRA is one of two methodologies widely used in Australian arboricultural risk reports (the other is TRAQ — Tree Risk Assessment Qualification). Accreditation is administered by QTRA Ltd and requires completing a recognised QTRA course and ongoing CPD.

See also: TRAQ, Visual Tree Assessment, Arborist

The controlled lowering of cut branches or sections using ropes, blocks, friction devices and ground-anchored lowering systems. Rigging is the difference between a clean urban removal and a chaotic one — instead of branches dropping freely, they're caught in mid-air and lowered to a controlled landing zone. Common gear: lowering line (e.g. Stable Braid or Tenex), rigging block, port-a-wrap or capstan friction device, slings and shackles, and a strong overhead anchor point. Loads in rigging can multiply quickly — a 200 kg log shock-loaded onto a static line can exert tonnes of force on the anchor. Rigging knowledge is the line between intermediate and advanced climbing.

See also: Running bowline, Felling, Climbing arborist

A climbing system where the climber ascends on a single rope fixed at the top, using mechanical ascenders or a friction hitch (typically a Hitch Climber pulley with Distel or Schwabisch) for grip. Replaced doubled-rope technique (DdRT) as the default ascent system across most Australian arborist crews over the last decade. SRT advantages: faster ascent, less rope friction in the canopy, better in tall trees, easier on the body. Trade-offs: more dependent on a single anchor (so anchor inspection is critical), and requires specific hardware that doesn't transfer perfectly to DdRT work positioning.

See also: Climbing arborist, Friction hitch, Blake's hitch (DdRT), SRT for Apprentices course →

Mechanical grinding of a remaining stump below ground level after a tree has been felled or removed. The grinder uses a rotating cutting wheel of carbide teeth to reduce the stump and surface roots to wood chips, typically down to 200 to 300 mm below grade. Australian sites usually require a Dial Before You Dig check before grinding — services run shallower than you'd expect and a grinder will go straight through irrigation, low-voltage cable and gas piping without slowing down. Specialist Australian stump grinding operators like All Sites Stump Grinding run dedicated stump-grinder fleets including narrow-access machines for residential properties. Stump grinder operation forms its own ticket and risk profile within arboriculture, and is a Knots-101-equivalent course coming on ARBCLUB in July.

See also: Felling, Owner-operator, Stump Grinders 101 (drops July) →

A calculated radius around a tree defined under AS 4970, inside which construction and excavation activity is restricted to protect the tree's root system and trunk. Formula: TPZ radius (m) = DBH (m) × 12, with a minimum of 2 metres and maximum of 15 metres for trees over 1 metre DBH. Most Australian council development applications require TPZ fencing, signage and exclusion of stored materials, machinery and trenching. Earthworks contractors that regularly coordinate with project arborists for tree-sensitive construction in South East Queensland include Dynamic Earth Solutions, who manage excavation and bulk earthworks while protecting TPZ-fenced retained trees. The Structural Root Zone (SRZ) is a tighter inner radius where root impact is essentially never allowed.

See also: AS 4970, DBH, Arborist (project)

A credential administered by the International Society of Arboriculture (ISA) for arborists conducting formal tree risk inspections and reports. TRAQ-qualified arborists use a structured assessment process (target, likelihood of failure, likelihood of impact, consequences) to arrive at a defensible risk rating. TRAQ is increasingly required for arboricultural reports submitted to councils, insurers and litigation processes in Australia — alongside or instead of QTRA. The qualification requires a multi-day course, an exam and ongoing renewal every five years.

See also: QTRA, Visual Tree Assessment, Arborist

A structured visual inspection method developed by Claus Mattheck for identifying tree defects and hazards. The method reads the tree's external symptoms (lean, bark inclusions, cavities, fungal fruiting bodies, root-plate movement, deadwood, included bark unions) as indicators of internal mechanical condition. VTA is the baseline pre-climb inspection every Australian climbing arborist runs before tying in — and it's the first step in every consulting arborist's risk report before any instrumented assessment (sonic tomography, resistance drilling) is brought in.

See also: QTRA, TRAQ, Hanger, Barber chair

An overhead hazard such as a loose branch, dead limb, hanging vine, broken-off top, or piece of bark sitting in the canopy ready to fall on workers below. The term is grim and accurate — Australian tree-industry incident records list widow makers as a leading cause of ground-crew fatalities and serious injuries. Pre-climb inspection has to systematically clear the canopy of widow makers before any work begins below, and the drop zone has to stay exclusion-zone until any identified hazard is brought down. The single biggest safety habit a tradie can build: always look up before walking under a tree on a job site.

See also: Hanger, Barber chair, Visual Tree Assessment