Called From Design to Reality, the second joint APL/SGD workshop was to take place at the Royal Botanic Gardens, Kew.
APL chairman James Steele-Sargent and garden designer Amanda Patton were to share their experience of working together to create a joint APL/SGD show garden.
Landform Consultants director Mark Gregory, who is chair of the APL Awards judges and an RHS judge, was set to join RHS chief assessor Andrew Wilson to give tips on creating a show garden.
During the event, visitors had the chance to visit the treetop walkway and enjoy aerial views of the capital's skyline.
Kew's head of arboretum and horticultural services Tony Kirkham was to explain how the treetop walkway developed from initial concept through to design, fundraising and building.