Category: Events

The Urban Tree Puzzle

The Urban Tree Puzzle

Urban Greening Efforts In Australia A Puzzle With Pieces Missing

Delegates at the Urban Tree Puzzle forum hosted by the Australian Institute of Horticulture at Botanica Nurseries in western Sydney learned how successful urban greening with trees requires all parts of the puzzle to work together when presenters Ross Clark of Impact Trees and Stuart Pittendrigh FAIH RH showcased best-practices in tree selection and establishment.


The ‘puzzle’ refers to the idea that tree establishment will only work in the long term if the following elements all work together:

  1. Planning: of the site, soil, species and logistics
  2. Species: ensuring that the species are suitable and resilient
  3. Provision: of high-quality trees and careful transportation
  4. Stock: specifically AS2303:2018 compliant stock
  5. Planting: ensuring the soil and root pruning methods are adequate
  6. Establishment and Maintenance: including post-planting watering and care
  7. Communication: across all elements and stakeholders


In many cases, major tree planting and greening efforts are getting most of these elements wrong and this means that the chances of long-term success are much lower than they could be. From poor quality stock, to the wrong species for the position, to a lack of post-planting care and watering, many trees are failing and this costs millions of dollars in lost opportunity and lost value, according to the speakers.


Ross Clark provided a highly-comprehensive presentation on the way that all parts of the Urban Tree Puzzle absolutely must fit together. To ignore or get wrong any single part often leads to the kinds of failures now being experienced across Australia as newly-planted or even established trees fail. Often, tree failure is blamed on storms or droughts where in reality, the real causes were apparent in the trees’ establishment and due to poor root development, poor root establishment or a failure to provide sufficient and thorough watering.


“There is no value in second-rate trees” said Ross. “You either use trees that have been grown to the Tree Stock Standard AS2303:2018 or you don’t plant at all. Second-rate trees have less than no value because the potential for failure is so high and you are likely to incur an opportunity cost by using bad tree stock”.


Stuart Pittendrigh FAIH RH is highly-regarded in the industry and consulted on the Barangaroo project that features more than 75,000 native trees and plants. Stuart spent weeks researching the plants that existed at the time of white settlement in 1788 and chose iconic native species, nearly all of which were endemic to Sydney Harbour with the added exceptions of Spotted gum, Gymea Lily, Sydney Blue Gum, Water Gum and  Callistemon citrinus “Anzac”.


Stuart outlined the enormous success of the effort that went into the Barangaroo ‘puzzle’, and perhaps the best evidence of its commercial success is that fact that less than one percent of trees failed when normally fifteen percent would be expected to fail. This is testament to the value of planning and the result is a vital and beautifully-planned precinct that matches the astonishing Sydney Harbour forefront.


This leaves you with one simple question: in your next landscape or urban greening project, will you make the effort to ensure that every part of the tree puzzle is properly planned?


Or will you simply hope for the best and pray that your energy and investment doesn’t keel over when the wind blows?




Tree Stock Standard Summary Guide

Tree Stock Standard Reference Card

Check your trees for compliance within the range accepted by AS2303:2018


Photo Gallery

Take a photographic tour through the workshop and share in the learnings from the AIH Urban Tree Puzzle…

It is with thanks to our Gold Sponsors Botanica Nurseries and General Manager David Hanna that the Urban Tree Puzzle was made possible. With gratitude.


Chris Poulton FAIH RH welcomed the delegates to the inaugural Urban Tree Puzzle event. The event aimed to build on recent outreach events around AS2303:2018 and its release in December 2018. It is with thanks to Chris and his tireless efforts that the Urban Tree Puzzle event could be made possible.


The event attracted a large group of professionals, members of the AIH and guests to learn from the experts on successfully establishing trees.


Ross Clark has been in tree production for decades and brought his charismatic expertise and knowledge to the event. Ross started by explaining the missed opportunity in current tree planting, and the challenges faced by time-poor developers in completing successful tree planting projects.


Ross presented each of the seven parts of the Urban Tree Puzzle where each individual part must work together to achieve successful tree establishment.


Ross further explained the absolute importance as an industry of pulling demand for AS2303:2018-compliant stock through the supply chain. As selectors and buyers, it is essential that every purchasing decision demands compliant stock in order to raise the quality of all trees sold into industry.


Ross built on the efforts by Western Sydney University in promoting the Tree Stock Guide (available at as a handy reference guide to using the AS2303:2018 standard in the field.


Stuart Pittendrigh FAIH RH presented a compelling overview of his work at the stunning Barangaroo site in Sydney. With his wide knowledge of trees and tree establishment honed over decades of experience, Stuart showed the sheer logistical challenge that it took to make Barangaroo such a beautiful venue.


Stuart also provided advice on successfully managing complex sites such as sloping landscapes with a combination of soft and hard landscaping and retaining techniques that provide depth and drainage needed to provide successful tree establishment.


General Manager of Botanica Nurseries, David Hanna, shared his thanks to Chris and the AIH team and guests for providing a highly-valuable workshop.


Ross then took guests on an outdoor tree assessment session, starting with four sizes of Tristaniopsis ‘Laurina’ trees.


Outwardly, all four appeared to be fairly good trees but a close inspection started to reveal some hidden issues…


This is the rootball from the smallest tree out of a six-inch pot. It certainly looked like a straight, upright tree with a good root to shoot balance. However, pulling out the soil shows clearly that the tree retains its tube-shaped rootball, indicating that it spent too long in the tube and the roots have grown downwards from the lower part of the tube rootball. This tree will continue to grow with these defects evident at a young age.


The next size tree was in an eight-inch pot and appeared quite good. However removing the soil showed that the rootball had curled around and not through the soil, creating a void directly under the stem-root junction. This is a problematic defect that will create stability and establishment issues.


This rootball is clearly far too long in the pot and has fully circled and bound the roots into a tight ball that requires significant remediation. Roots like these would continue to circle even with significant root pruning.


It proved difficult to loosen these roots, demonstrating how tightly-bound the rootball had become.


Ross showed the practice of using a handsaw to remove the outer spiraled roots, peeling away matted roots like carpet. This then forces new tip growth that grows outward and aims to remove the circled root growth.

Mount Tomah & Wood Green With The HMA

Mount Tomah & Wood Green With The HMA

Members and guests of the Australian Institute of Horticulture and the Horticultural Media Association ventured to the beautiful Blue Mountains Botanic Garden at Mount Tomah north-west of Sydney on February 23rd as part of the HMA Tour series.


Famous as Sydney’s cool-climate botanic garden, Mount Tomah is in wet eucalypt rainforest on 250 acres of beautiful gardens and natural bushland. Its oldest living trees are more than 200 years old and include Blue Mountains Ash (Eucalyptus oreades), Golden Sassafras (Doryphora sassafras), Coachwood (Ceratopetalum apetalum), Black Ash (Eucalyptus sieben), Sydney Peppermint (Eucalyptus piperita), and Sydney Red Gum (Angophora costata). Many of the exotic trees were planted by the previous owners before they bequeathed it to the NSW Government as a botanic garden and there are many fine established trees.


Guests were given a wonderful tour by horticulturists Greg Bourke and Mat Murray whose passion and incredible enthusiasm shone through the rain. Mat is especially passionate about bulbs and shared his favourite ten bulbs including the blue crocus of the Turkish mountains and species tulips with camouflaged leaves.


Greg’s favourite dahlia trials to see which varieties do well in the Mount Tomah climate. Doubles, singles, pompoms, they are really wonderful plants.

These are the natural shapes that basalt forms inside lava tubes as it slowly cools into hexagonal columns. The gardens make extensive use of it as paving, wall rock and vertical columns for fantastic visual impact. It’s really striking!

Gorgeous maples on show and they now replant the self-sown seedlings to sell to the public.

Great use of natural rock, heat-tolerant cover plants and shrubs.

Plants with real bite. Greg shared that the carnivorous plants literally doubled the visitation at the city botanic garden and these are most amazing plant for gaining the interest of kids and parents alike. The marsh here was gurgling with frog calls.

Sensational bedding displays of mixed Gerberas neat the visitor centre.

Then we headed downhill to the sensational garden at Wood Green where owners Peta and Peter Trahar shared their home and garden of 33 years. The Trahars are well-known for staging the original Plant Collector’s Fair that was held at Wood Green in Bilpin from its inception in 2004 until 2011 where it took on a new scale at the showground at Clarendon. Peta curates a wonderful garden of hard-to-find perennials, shrubs, trees and extensive acreage lawns that surround the home and farm buildings.

Peta’s famous Phlox is one you don’t see much of in gardens anymore but a real standout.

Peta is a professional landscape architect, photographer and writer and it really shows in her planting styles.

Wood Green has more than 28 zones including these beautiful vistas under the trees, the ideal resting spots on a wandering tour.

Open lawns open onto a deep green valley of towering eucalypts.

Many thanks to Judy Horton MAIH RH, Matt Carroll MAIH RH, and all HMA and AIH members and guests for coming along.

Greenwalls and Rooftops (Including Community and Food Usage Visit)

Greenwalls and Rooftops (Including Community and Food Usage Visit)

Mark Paul MAIH RH, one of Australia’s leading Greenwall experts took us on a guided tour of some iconic greenwalls in Sydney. Visiting the Calyx in the Botanic Gardens, Inner City sites and the Broadway greenwall.

Sincere thanks to organiser Chris Poulton MAIH RH, Mark Paul MAIH RH and all members and guests that came and enjoyed a truly fabulous event.


Image credit David Ting MAIH RH 2018 — at Central Park Sydney.


Green wall display at the Royal Botanic Gardens.


Image credit David Ting MAIH RH 2018 — at Central Park Sydney.


The beautiful display that is The Calyx – one of the finest vertical plantings you will ever see.


Image credit David Ting MAIH RH 2018 — at The Calyx.


Plants with bite!


Image credit David Ting MAIH RH 2018 — at The Royal Botanic Garden, Sydney.


The other Costa.


Image credit David Ting MAIH RH 2018 — at The Royal Botanic Garden, Sydney.


Green roof


Image credit David Ting MAIH RH 2018 — at Central Park Sydney.


Image credit David Ting MAIH RH 2018 — at The Calyx.


Image credit David Ting MAIH RH 2018 — at The Calyx.


Image credit David Ting MAIH RH 2018 — at The Royal Botanic Garden, Sydney.


Image credit David Ting MAIH RH 2018 — at The Royal Botanic Garden, Sydney.

Walk and Talk Barrenjoey

Walk and Talk Barrenjoey

Friday 22nd June a great enthusiastic group of AIH members as well as other guests attended our first walk and talk event for the year headed up by Mark Paul of The Greenwall Company and former AIH Horticulturist of The Year.

Our group met at the Barrenjoey boathouse where we grabbed a coffee before heading off on our walk along the foreshore looking at the changing vegetation and witnessing some of the introduced weeds in the exposed areas. Next, we set off up the steep pathway which ultimately leads to the Barrenjoey lighthouse. Along the way, Mark imparted his vast knowledge of native plants and how their specific characteristics enable them to do so well in this environment.

The day also provided opportunities to be able to discuss with one another just how this relates to us in our day-to-day work as horticulturists.

Overall the day was a great success and our hope is that these days can provide our members with a chance to visit different horticultural venues learning from experienced horticulturists as well as being able to discuss with one another specific horticultural problems and issues we might be encountering.

We hope to organise another one or two later this year. Details to be announced soon. A big thank you to Mark Paul for his time, passion and knowledge.

By Chris Poulton FAIH

AIH members and guests on their walk and talk Photo – Chris Poulton FAIH

AIH members and guests reaching the top of Barrenjoey – Photo Chris Poulton FAIH

Barrenjoey- Photo Chris Poulton FAIH