Tim Johnson

INTRODUCTION

Treenet was established in 1997 to help to develop and implement solutions to perennial issues which compromise urban forestry, urban development and the quality of urban life. Treenet’s Vision broadly defines the organisation’s sphere of operation: “to enhance the urban natural environment through the successful selection, production, establishment and management of street trees.”

Treenet developed six aims, based on research and education functions, to enable it to achieve its vision (Treenet Inc. Constitution, Section 3.2). Section 3.2.3 of the Constitution details one of these aims: “to liaise with Local Government and other appropriate entities to establish and monitor street tree trial sites testing species and engineering techniques”. Trial planting began in 1997.

Treenet has devoted considerable time and resources to encouraging and supporting tree trial planting. Past symposium proceedings document a range of tree trial matters in papers presented by local government officers, academics and nursery industry representatives from across the country, see Gardner (2003), Nicolle (2002), Schumann (2004), Watt (2005), See (2003), Hay, Johnson, and Kirwan (2002), Fitzgibbon (2003) and Oldrey (2003). This paper updates information relating to a selection these early trials.

During Treenet’s early years trial site protocols developed to become more integrated with urban civil engineering. A number of papers presented at recent symposia have focussed on “tree sensitive urban design”, see Plant (2002), Argue (2006), Taylor (2006), Wettenhall (2006). Given the conflicts between trees and built infrastructure it was inevitable that their interfaces would become the focus of increased research, and that urban design research and development will combine civil engineering and urban forestry tree species trials. This paper summarises some current integrated engineering and urban forestry research.

The City of Mitcham has a rich history of street tree planting and has established streetscapes which support a broad range of species. Mitcham’s approach to tree asset management has helped to identify mature examples of species that are not commonly planted, and others which are possibly unique, of which some show considerable potential for increased planting in urban areas. This paper presents some of these species as having potential for increased trial planting.

EARLY TRIALS

Treenet’s website contains information on some of the earliest street tree trials. From the beginning it has proved difficult to get practitioners to volunteer information and upload it to the website. Ten years after the initial plantings the value of these trials is becoming more apparent, as is the need to increase the rate of information contribution.

To reduce the risk associated with trial planting, many of the early species selections were influenced by the apparent suitability of mature examples growing in the Waite Arboretum. These selections included wilga (Geijera parviflora), leopard tree (Caesalpinia ferrea), zelkova (Zelkova serrata), pears (Pyrus spp.) and crow’s ash (Flindersia australis).

Many of the early plantings were established in the City of West Torrens, where species could be planted in some of the densest clays in South Australia (Keswick), the lightest sands (Netley) and highly productive loam (Lockleys). A preliminary summary of West Torrens’ trials up to 2002 was presented at the 3rd National Street Tree Symposium, see Hay, J., Johnson, T., and Kirwan, L., (2002). Appendix A summarises the current status of trial plantings in West Torrens.

Of the types included in the early West Torrens trials, some were planted in low numbers out of general interest or for special applications on reserves rather than in anticipation of suitability for general street use. Trials in other councils (e.g. Mitcham, Burnside, Charles Sturt) show additional species may also have considerable potential for increased use as street trees.

SPECIES SUITED TO BROADER TRIAL PLANTING

Of the species and varieties planted as trials to determine suitability for increased street planting, some have demonstrated that further planting is warranted and others have shown a degree of potential but this has varied across the specimens. Trials in other councils (Mitcham, Burnside, Charles Sturt) show additional species may also have considerable potential for increased use as street trees. Species which show considerable potential for further planting in Adelaide are listed in Table 1.

Trees listed in Table 1 have proved to be suitable for a range of conditions encountered in metropolitan Adelaide and surrounding areas. TREENET encourages members to become more familiar with these species, to note examples encountered in the field and to consider their characteristics when planning street planting projects. TREENET encourages further trials involving these species in appropriate locations across Adelaide and areas with similar environmental conditions.

Species Notes
Acacia melanoxylon  Blackwood Hardy with moderate to rapid growth rate on clays and loams.
Angophora hispida  Dwarf apple-myrtle Mature examples on sand have demonstrated suitable form and considerable longevity, may be difficult to source stock.
Brachychiton acerifolius  Illawarra flame

Brachychiton populneum  Kurrajong

Brachychiton rupestris  Queensland bottle

May be slow growing but are long lived, B. acerifolius and B. populneum typically develop substantial root flare; all three species require considerable space.
Corymbia eximia  Yellow bloodwood Uncommon as street trees but mature examples scattered across Adelaide show their potential.
Cupaniopsis anacardioides  Tuckeroo Likely to remain medium size though potentially a large tree, ensure that nursery stock has perfect structural characteristics, may be best suited to mulched garden or nature strip areas.
Flindersia australis  Crow’s ash Expected to be medium size as a street specimen but potentially a large tree, large woody fruits, could be used to form a substantial/landmark avenue.
Geijera parviflora Wilga Hardy small to medium size tree, avoid planting in turf.
Lagerstroemia indica x fauriei varieties, Indian Summer crepe myrtles:

“Biloxi”, “Natchez”, “Sioux”, “Tuscarora”

Trial in small spaces in hot locations, may require regular pruning to establish a suitable structure.
Pistachia chinensis  Chinese pistachio Mature examples in Adelaide plains streets demonstrate suitability though performance on shallow and alkaline soils is poor, difficult to obtain stock with a single straight leader.
Pyrus calleryana varieties All varieties have grown well in Adelaide, avoid varieties and stock with acute branch angles as failure can be expected.
Quercus canariensis  Algerian oak

Quercus cerris  Turkey oak

Quercus robur  English oak

Plan adequate space to plant these species as a feature in new developments, consider potential hazard associated with acorns, plant as a long term investment.
Quercus ilex  Holly oak

Quercus suber  Cork oak

Ensure adequate space and sufficient resources to maintain during long establishment
Sapium sebiferum  Chinese tallowwood Substantial root flare, needs a medium size space for a small to medium tree, grows well in Adelaide’s clays, loams and sands.
Sophora japonica  Japanese pagoda tree Many mature examples in the CBD and through North Adelaide’s streets

Table 1:  Trees with potential for increased use in Adelaide streets.

Corymbia eximia, North Plympton, 8 years

Stenocarpus sinuatus, Lockleys, 8 years

Cupaniopsis anacardioides, Lockleys, 8 years

Corymbia ficifolia x ptychocarpa” Summer Red”, Lockleys, 8 years

Harpullia pendula, Lockleys, 8 years

 

 

Geijera parviflora, Plympton, 9 years

 

 

Brachychiton acerifolius, Richmond

Flindersia australis, Kurralta Park, 9 years

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Elaeocarpus reticulatus, Plympton, 9 years

Flindersia australis, Kurralta Park, 9 years

 

 

 

 

 

 

 

 

 

 

 

Lagerstroemia indica x fauriei “Tuscarora” City of Charles Sturt

Caesalpinia ferrea, Lockleys, 7 years

 

 

 

 

 

 

 

 

Some examples of trees listed in Table 2 have demonstrated potential suitability to conditions encountered in metropolitan Adelaide and surrounding areas but results have been inconsistent to date or have identified possible limitations in street planting.  TREENET encourages members to consider planting additional small scale trials of these species in appropriate locations where issues which may arise will remain manageable.

Species Notes
Acer buergerianum   Trident maple

Acer monspessulanum  Montpelier maple

 

Consider for locations where litter will not reach waterways.
Acer x freemanii “Jeffersred”  Autumn Blaze hybrid maple Avoid compacted heavy soils, ensure adequate moisture.
Castanospermum australe   Black bean Survival and growth rates have proved acceptable but only a small number of trial trees have been planted, after 10 years still too early to determine suitability.
Elaeocarpus reticulatus   Blueberry ash Appears hardy, mature size may result in minimal visual impact except in close plantings in small streets.
Ginkgo biloba  Maidenhair tree

 

Has shown to be relatively hardy, growth rates vary considerably.
Harpullia pendula  Tulipwood Small to medium attractive tree, fruits attractive when on the tree but may result in litter issues/concerns in pavement.
Zelkova serrata  Japanese zelkova Appears hardy though may be high maintenance when young, smaller stock appears more vigorous.

Table 2: Trees worthy of consideration for continued planting on a limited trial basis

MITCHAM’S ENGINEERING AND SPECIES TRIALS

The City of Mitcham has supported TREENET since its formation and has been involved in associated research for several years. Treenet trials began in Mitcham in 2003 with tree planting and civil engineering works. Several tree species have been planted on a trial basis in Mitcham, including Wilga (Geijera parviflora), Low-fruiting white cedar (Melia azedarach “Elite”), “Goolwa Gem” (Eucalyptus leucoxylon “Goolwa Gem”) and Sapporo elm (Ulmus “Sapporo Autumn Gold”). Initial planting of locally selected Eucalyptus erythronema and Eucalyptus albopurpurea occurred in Mitcham in 2007. Further street tree trial planting is planned.

Mitcham embraces the concept of integrating arboriculture with civil engineering to the benefit of both disciplines and the community. As an example, in partnership with the University of SA, Treenet’s Gold Sponsor 2007: the Department for Transport, Energy and Infrastructure, and Treenet, Council is undertaking an ongoing stormwater harvesting trial in Claremont Avenue at Netherby, which directs runoff from the road into tree root zones to encourage root development in nature strips in order to promote tree health and avoid infrastructure damage (Wark 2003, Porch, Zanker and Pezzaniti, 2003).

Monitoring of the harvesting systems shows that the moisture content of the upper 700mm to 800mm of soil varies rapidly in response to changing climatic conditions. Moisture content below this depth appears more consistent. Tests reveal the gravel filled trenches empty over a period of thirty three hours; an infiltration rate consistent with typical clay soils of the region.

While preliminary results indicate the systems have value they have also revealed issues regarding the serviceability of the infrastructure. The permeable paving and Terrabond systems became unserviceable within four months of operation due to blockage resulting from accumulated sediments. The serviceability of the modified side entry pit system may also have been reduced through partial blockage by coarse sediments. Data recorded to date is insufficient to allow modeling to determine water quality and quantity improvements.

Measures being considered to progress stormwater harvesting for use by street trees include modification of trials using permeable paving and Terrabond, interception of stormwater discharge from adjoining dwellings before it reaches the road, upgrading monitoring of the modified side entry pit system, alternative design solutions utilizing biological activity (plant root growth) to maintain surface permeability, and modeling water quality and quantity improvement when sufficient data has been collected.

Another current project involves installing aggregate-filled drainage trenches in Doncaster Avenue at Colonel Light Gardens to assist stormwater management and the long term health of this significant historic avenue of river red gums (Eucalyptus camaldulensis). The project resulted from consultation regarding related infrastructure works, which revealed that the majority of residents saw maintenance of the avenue as of prime importance despite the reputation of the species. Consequently some tree-friendly engineering solutions were developed, most of the established trees were preserved and additional trees are soon to be planted. Figure 1 below details the stormwater management technique being tested; time will reveal any impacts of the additional water on the trees and civil infrastructure.

Figure 1: Stormwater harvesting trial detail to support heritage trees in Colonel Light Gardens.

In the period between 2003 and 2007 an audit of the City of Mitcham’s urban forest noted the location, size and condition of street trees.  Some relatively uncommon species were audited and some unidentified eucalypt species were also recorded.  Examination of these suggested that many may be survivors from the “go native” plantings of the 1970s.

The established, mature specimens of some of these species display the desirable characteristics of hardy, sustainable street trees.  They are of useful size and are attractive specimens.  They have suitable structures and balanced canopies; they exhibit minimal conflict with built infrastructure, and they are of reasonable age and remain in good health.  These trees continue to function well in their streetscapes with minimal maintenance.  Seed has been collected from these examples for propagation, planting and further selection.

Some of the eucalypt species could not be readily identified in the field.  Positive identification by Mr. Dean Nicolle confirmed that many were hybrids.  Of the uncommon species observed, several show considerable potential for further street planting including: Yellow-flowered mallee (Eucalyptus macrandra), Tall sand mallee (Eucalyptus eremophila), Port Lincoln mallee (Eucalyptus albopurpurea), Two winged gimlet (Eucalyptus diptera) and Eucalyptus cuspidata.

Eucalyptus eremophila

Eucalyptus cuspidata

 

 

 

 

 

 

 

 

Eucalyptus erythronema

Eucalyptus erythronema

 

 

 

 

 

 

 

 

Eucalyptus orthostemon

Eucalyptus albopurpurea

 

 

 

 

 

 

 

 

Variability including hybridisation is a concern when selecting eucalypts for street planting.  To aid the development of suitable forms, species selected for trial planting in Mitcham will initially be planted in small numbers in streets and in clusters on reserves.  If reserve plantings develop into acceptable specimens, seed will then be collected from the best examples near the centers of the clusters where the likelihood of cross pollination is minimal.  A second quality control will be to grow on seedlings selected for their consistency.  It is hoped that further selection for consistency at the time of planting will aid the development of increasingly uniform specimens.  The capacity to attach notes to Council’s tree asset register and to use it to flag future works is fundamental to continuing the tree selection program beyond the tenure of existing staff.

APPENDIX A: Tree Trial Summary by Species

The notes which follow are adapted from Hay, Johnson & Kirwan (2002).  2002 notes reflect early trials of the species in the City of West Torrens.  2007 notes summarise broader local experience based on the trials planted in the City of West Torrens and observations in other areas across metropolitan Adelaide.  The contribution of staff of the City of West Torrens, particularly the Coordinator of Horticultural Operations: Lisa Kirwan, in updating these notes is acknowledged and appreciated.

Acacia melanoxylon Blackwood.
2002 – survival rate: acceptable, growth rate: acceptable.
2007 – appears generally hardy in a range of soils, moderate to fast growth rate, drought tolerant once established, indigenous in some Adelaide & Mount Lofty Ranges niches, structure reasonable for street planting, could be more widely considered for trial planting across the species’ natural range, should be considered for planting in appropriate streetscapes.

Acer buergerianum Trident maple
2002 – Survival rate: variable, growth rate: variable.
2007 – High survival rate and moderate growth rate in medium to heavy soils, no specimens survived in neutral-acid sand, trees planted in chalky limestone in City of Prospect (exposed site, reflected heat, vehicle emissions) continue to perform acceptably after ~15 years, prolific seed set, potentially invasive, appears likely to remain as a small tree in street situations, expected mature height 5-6m.

Acer monspessulanum Montpelier maple
2002 – Survival rate: uncertain, growth rate: uncertain (small scale trial, stock quality poor).
2007 – A range of factors contributed to unsuccessful performance of the trial, trial inconclusive, examples in the Waite Arboretum suggest the species deserves further attention & establishment of further small scale trials.

Acer pseudoplatanus Sycamore
2002 – Survival rate: acceptable, growth rate: variable.
2007 – growth is stunted under local conditions, little development in excess of 3m in height, generally poor vigor due to environmental conditions, prolific seed set, species is an environmental pest in some regions with reliable moisture.

Acer x freemanii “Jeffersred” Autumn Blaze hybrid maple
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Initial good growth rate slowed after 3rd year when supplementary watering ceased, performance appears significantly better in Lockleys trial (sheltered reserve location, fertile loam, supplementary watering still required & provided at times ) compared to Plympton (arterial road, clay), used with reasonable results in some Adelaide Hills regions and in acidic sand at Victor Harbor SA, additional trials might be considered in areas with deeper/richer soils and higher moisture levels than Adelaide plains.

Backhousia citriodora Lemon-scented myrtle
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Growth rate remains slow, health poor, specimens persevering not thriving, possibly useful in garden situations but appears not hardy enough to contribute to Adelaide streetscapes.

Banksia integrifolia Coast banksia
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Variable survival and growth rates on light-medium soils, may be less reliable on heavy soils, considerable variability in form and likely variability in mature size, respectable performance on sandy soils, could be considered for small scale or isolated plantings.

Brachychiton acerifolius Illawarra flame tree
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Hardy, reliable and long lived though considered by some to have a slow growth rate, growth rate concerns may be overcome through use of advanced stock, a medium size tree with robust root system needing considerable space, could be considered for widespread planting in appropriate streetscapes with adequate space.

Brachychiton populneum Kurrajong and
Brachychiton rupestris Queensland bottle
As for Brachychiton acerifolius

Buckinghamia celsissima Ivory curl tree
2002 – Survival rate: variable, growth rate: variable.
2007 – Growth stopped at ~2.5m in height, potential issues with bees which are attracted in large numbers to flowers (twice per year), grows best when sheltered, exposed plants generally wind affected, prevailing winds observed to stunt foliage on windward side while still growing lush new shoots on sheltered side.

Caesalpinia ferrea Leopard tree
2002 – Survival rate: acceptable, growth rate: uncertain.
2007 – Appears variable and unreliable, attractive bark, best specimens are attractive but of low visual impact, insufficient to provide adequate street amenity.

Castanospermum australe Black bean
2002 – Survival rate: variable, growth rate: variable.
2007 – Trees still obviously immature, reasonable health and vigor, likely to develop into attractive mature shade/street trees though more time needed to determine suitability, good structure essential when selecting stock.

Cercis canadensis Redbud (seedling variety)
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Many examples removed due to poor structure, prolific seed set, hardy small tree though with limited street appeal. “Forest Pansy” variety relatively reliable though short stature and broad spreading nature restrict usefulness in street situations.

Corymbia eximia Yellow bloodwood
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Hardy medium size tree, retains reasonable growth rate once established without additional watering, attractive street tree, appears to tolerate a broad range of soil types, structure variable though generally manageable, should be considered for increased use as street and park tree.

Corymbia ptychocarpa x ficifolia “Summer Red”
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Growth rate slows considerably when supplementary watering ceases, profuse flowering appears to stunt mature size, best examples developed in light soils but still only reached ~2.5m tall after 9 years, neat & compact specimens, limited street appeal due to small size, ongoing issues with basal suckers, very poor performance in heavy soil.

Cupaniopsis anacardioides Tuckeroo
2002 – Survival rate: acceptable, growth rate: variable.
2007 – Generally hardy tree with variable growth habit, some structural problems including wind damage, considerable litter production, better examples grown in loam, quality stock worthy of continued small-scale trials.

Elaeocarpus reticulatus Blueberry ash
2002 – Survival rate: acceptable, growth rate: variable.
2007 – Upright growth habit, generally good health and vigour, street appeal of mature specimens unknown, more time required to determine whether further trials are advisable.

Eucalyptus leucoxylon “Euky Dwarf”
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – “Euky Dwarf” now recognised as Murray Bridge form of the species, hardy, reliable medium size tree with less variation than the species, worthy of further trial planting.

Flindersia australis Crow’s ash
2002 – Survival rate: variable, growth rate: variable.
2007 – Reliable survival and growth characteristics, large tree, woody fruits, dense shade tree, worthy of increased planting where space is adequate.

Flindersia xanthoxyla Yellow wood
2002 – Survival rate: poor, growth rate: poor.
2007 – One trial location only in an exposed position in a broad median, slow growth rate was unacceptable, the few surviving specimens were removed after year 3.

Fraxinus ornus Manna ash
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Unreliable in poor, shallow or compacted soils, reasonable performance in quality soil, expected mature height 5 – 7m, seed set may become an issue, generally unsuited to widespread street planting in Adelaide except in sheltered locations in quality soil with reliable moisture.

Fraxinus ornus “Arie Peters” “Arie Peter’s” Manna ash
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Flowers more profusely than seedling variety but appears less tolerant of drought and heat, sooty mould a regular nuisance, appears less hardy overall than the seedling variety.

Fraxinus ”Raywood” grafted to F. ornus rootstock Claret ash
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Hardy and reliable small to medium tree under a broad range of streetscape conditions, considerably less vigorous than specimens grafted on F. angustifolia rootstock, expected mature height 5 – 6m.

Fraxinus velutina Velvet ash
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Appears hardy, some examples exhibited structural problems particularly weaknesses at forks, prolific seed set may become an issue (female trees), many examples removed in first decade, possibly consider for limited further trials with male specimens selected for improved structure.

Geijera parviflora Wilga
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Possibly the best trial species by Treenet so far, initial concerns with slow growth rates proved unwarranted except when planted in turf, current nursery stock is of improved structure, formative pruning essential to encourage vertical growth of young trees, drought hardy except in turf, no pest or disease issues observed, should be more widely planted.

Ginkgo biloba Maidenhair tree
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Species appears reasonably hardy although growth rate diminished when supplementary watering ceased, brittle and susceptible to damage especially when young, possibly consider for further trial planting in higher rainfall areas.

Gleditsia tricanthos “Elegantissima” Honey locust
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Performance poor when supplementary watering ceased, appears unlikely that the species will be suited to street planting under Adelaide’s environmental conditions.

Harpullia hillii
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Very little lateral branch development, some examples reaching 6m without lateral branching, complaints regarding litter (sticky fruits), appears hardy in alluvial soils, more time required to ascertain value in further trial planting, further trials unlikely at this stage.

Harpullia pendula Tulipwood
2002 – Survival rate: acceptable, growth rate: poor.
2007 – Specimens brittle and susceptible to damage when young, some examples developing into attractive trees in West Torrens, Marion and elsewhere, potential for further planting in Adelaide.

Lagerstroemia indica x fauriei varieties, Indian Summer crepe myrtles: “Biloxi”, “Natchez”, “Sioux”, “Tuscarora”
2002 – Consistent results with all varieties: Survival rate: acceptable, growth rate: acceptable.
2007 – Hardy small trees, best suited to very small locations, readily trained to upright specimens through relatively simple pruning.

Pistachia chinensis Chinese pistachio
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Mature examples prove that the species can work well as a street tree, nurseries advise that growing quality stock can be difficult, ensure stock is of single leader with good caliper and taper, if you find some good stock – buy it.

Pyrus calleryana “Bradford”, “Capital”, “Chanticleer”, “Lynington”, “Winterglow”
2002 – Consistent results with all varieties:, Survival rate: acceptable, growth rate: acceptable.
2007 – All varieties have grown well in Adelaide and environs, early forms demonstrated structural issues, seedling variety is a broad spreading shade tree, may be issues with fruit fall.

Pyrus ussuriensis Manchurian pear
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – A reliable species under Adelaide’s conditions, fruit may cause concern.

Quercus canariensis Algerian oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Developing into robust specimens, no problems or issues identified, species is a long term investment even after planting advanced stock, should be planted more across Adelaide where space is sufficient.

Quercus cerris Turkey oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – As for Q. canariensis

Quercus coccinia Scarlet oak
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Unreliable, typically poor in streets on the Adelaide plains though some few reasonable mature examples exist in private gardens. Appears more reliable in Mt Lofty Ranges, though with climate change this may not be so in the future.

Quercus ilex Holly oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – As for Q. canariensis, though growth rate of Q. ilex appears slower.

Quercus palustris Pin oak
2002 – Survival rate: acceptable, growth rate: poor.
2007 – As for Q. coccinia

Quercus robur English oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Developing into robust specimens, no problems or issues identified, species is a long term investment even after planting advanced stock, should be planted more across Adelaide where space is sufficient.

Quercus robur “Fastigiata” Fastigiate English oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Appears less robust and requiring more moisture than seedling Q. robur

Quercus suber Cork oak
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – As for Q. canariensis

Robinia x decaisneana Pink wisteria tree
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Fast growing tree, attractive & hardy, most examples removed in early years due to major problems with root suckers & thorns.

Sapium sebiferum Chinese tallowwood
2002 – Survival rate: acceptable, growth rate: variable.
2007 – Developing into robust specimens, no problems or issues identified.

Sophora japonica Japanese pagoda tree
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Hardy attractive species, high maintenance when young but reducing with maturity.

Sophora japonica “Princeton Upright” “Princeton Upright” pagoda tree
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – As for seedling variety, good structure, flowers profusely.

Stenocarpus sinuatus Firewheel tree
2002 – Survival rate: acceptable, growth rate: uncertain.
2007 – Slow/variable growth rate, unreliable performer, little street appeal after ten years.

Fraxinus pennsylvanica “Urbanite” “Urbanite” green ash
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Issues with suckering from rootstock, trial removed during major infrastructure project, suitability undertermined.

Tilia cordata ‘Chancole' Chancellor
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – Specimens surviving not thriving, stunted, unsuitable for street planting.

Toona australis Australian red cedar
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – extreme sun scorch on western side of trunk though growth still reasonable in season, unlikely to thrive in Adelaide’s streets but may be worthy of further consideration in sheltered & well watered reserves.

Zelkova serrata Japanese zelkova
2002 – Survival rate: acceptable, growth rate: acceptable.
2007 – Variable & uncertain, some trials (small bare-root plantings) performing acceptably but others (advanced container stock) appear stunted, more time required to assess trials.

Zelkova serrata “Green Vase” “Green Vase” Japanese zelkova
2002 – Survival rate: uncertain, growth rate: uncertain.
2007 – As with seedling variety.

REFERENCES

  • Argue, J., 2006. Going With The flow: Trees, Habitat and Urban Waterways. Treenet Proceedings of the 7th National Street Tree Symposium: 7th and 8th September 2006.
  • Fitzgibbon, J., 2003. Treenet Trials, A Tree Grower’s Perspective. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003
    Treenet Inc.ISBN 0-9775084-3-9,
  • Gardner, J., 2003. Oaks for the Adelaide Plains: Successful Species in the Waite Arboretum. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003
    Treenet Inc.ISBN 0-9775084-3-9,
  • Hay, J., Johnson, T., and Kirwan, L., 2002. Street Tree Trials in the City of West Torrens, Proceedings of the 3rd National Street Tree Symposium: 5th & 6th September 2002.
  • Nicolle, D., 2002. Eucalypts with Potential for Streets. Treenet Proceedings of the 3rd National Street Tree Symposium: 5th and 6th September 2002. ISBN 0-9775084-2-0, Treenet Inc
  • Oldrey, L., 2003. Adelaide’s Street Trees: Past, Present and Future. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003. Treenet IncISBN 0-9775084-3-9,
  • Plant, L., 2002. Constructing Root Space for Trees in Australian Cities. Treenet Proceedings of the 3rd National Street Tree Symposium: 5th and 6th September 2002. Treenet IncISBN 0-9775084-2-0,
  • Porch, S., Zanker, J., and Pezzaniti, D., 2003. Stormwater Harvesting Trials for Irrigation of Street Trees and Water Quality and Quantity Improvement. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003. ISBN 0-9775084-3-9, Treenet Inc
  • Schumann, D., 2004. Management of Urban Forests in Remote and Arid Environments
    Treenet Proceedings of the 5th National Street Tree Symposium: 2nd and 3rd September 2004
    ISBN 0-9775084-4-7, Treenet Inc
  • See, M., 2003. Street Tree Trials – Avenues of Interest. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003, ISBN 0-9775084-3-9, Treenet Inc
  • Taylor, K., 2006. Improving the urban Forest by Design. Treenet Proceedings of the 7th National Street Tree Symposium: 7th and 8th September 2006.
  • Wark, A., 2003. Stormwater Harvesting Trial – Claremont Avenue, Netherby. Treenet Proceedings of the 4th National Street Tree Symposium: 4th and 5th September 2003, ISBN 0-9775084-3-9, Treenet Inc
  • Watt, S., 2005. Treenet: New Tree Variety Assessment. Treenet Proceedings of the 6th National Street Tree Symposium: 1st and 2nd September 2005
    ISBN 0-9775084-5-5, Treenet Inc.
  • Wettenhall, G., 2006. Green Streets: Creative Stormwater Design. Treenet Proceedings of the 7th National Street Tree Symposium: 7th and 8th September 2006.

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