I often am asked for information about landscape architecture and refer people to these websites:
American Society of Landscape Architects
Australian Institute of Landscape Architects (AILA)
Landscape Institute | Inspiring great places (UK)
Landscape Architecture Foundation
These sites includes links to the professional association website for landscape architects in Australia, UK and the USA. The Landscape Architecture Foundation is a research body set up to “increase the capacity of landscape architects to solve the environmental crisis”.