TREENET research and education cluster pioneers trials of trees suitable for South Australian streets
The Adelaide' based national research and education cluster TREENET initiated the search for species such as wilga assuitable South Australia street trees . Other street species trialled and introduced to Adelaide suburbs through TREENET were the Chinese pistachio (top left: examples in Herbert Road, Ashord, pictured in 1999 and 2020) and ivory curl (bottom: in Kurralta Park, pictured in 2000, 2015 and 2018.)
Images courtesy TREENET
David Lawry and Tim Johnson, two key figures in TREENET (Tree and Roadway Experimental and Educational Network), founded in Adelaide in 1997, crossed paths in their separate searches to find species suitable as street trees in South Australia.
The native species wilga (geijera parviflora), unknown to the many South Australian nursery staff in 1990s, had separately interested both Lawry and Johnson as a suitable street tree for South Australian conditions. Lawry, a nurseryman, and Johnson, a local government horticulturalist, were both passionate about supporting trees in urban nature.
Lawry’s search for the wilga species paid off from a road trip to Queensland where he found forestry tubestock that he brought back to South Australia in his Kombi van. Lawry and Johnson first met at a local government expo stand where the wilga saplings were displayed. That meeting led in 1997 to what was possibly the first trial planting of wilga as a street tree in South Australia. TREENET also was started in 1997 with Lawry as a founder and Johnson starting as a volunteer and later becoming a director.
Those initial plantings of wilga in Adelaide matured into healthy attractive street trees in the verges of the western end of Garfield Avenue in the suburb of Plympton. Wilga became a stock item for many commercial nurseries and thrived in streets in cities and towns in arid and semi-arid zones across Australia.
Chinese pistachio (Pistacia chinensis) was another early trial street tree species promoted by TREENET. This was inspired in 1999 by an example of it growing in a street in Adelaide suburban Ashford, having been planted by a resident 32 years previously. A picture of the Ashford example at the 2000 TREENET symposium led to discussions with commercial growers that made the speciea increasing available. Early trial stock quality was highly variable but, within a few years, good examples became readily available. Several larger and older examples were later found in Angaston in South Australia’s Barossa Valley, showing its resilience as a street tree.
Ivory curl (Buckinghamia celsissima) was an unlikely candidate for a South Australian street tree species trial but Lawry liked the species’ appearance and knew it grew in Sydney and Melbourne so he brought some to try in Adelaide’s hot dry clay. This northern Queensland species of the Proteaceae family was expected to handle Adelaide’s heat but its performance in low humidity and poorly draining soil was unknown. Cold westerly winds affected only juvenile trees and, after two decades, they grew full and balanced canopies.
TREENET’s trial success with wilga, Chinese pistachio and ivory curl as street trees had to be backed up by long-term work with nurseries and local government – and younger generations – for it to be extended to other species.
