Trees in high density cities

Department: Landscape Architecture
Active Dates: January 2010 – 2017

Project team:
P-I: Matthew Pryor, HKU
Co-I: Dr. Gary Watson, Head of Research, Moreton Arboretum, Champaign Illinois, USA; Li Wei – Research Associate, HKU

Project funding:
Tree Transplanting Metrics.  General Research Fund.  


From the outset, Hong Kong has had a highly compact urban form.  Green spaces within the city have typically been very small and infrequent, street corridors are highly contested environments (in plan and section).  Huge spatial and operational challenges have to be overcome in order to maintain any significant greenery or urban forest.  This research initiative explores a broad spectrum of technical and operational issues involved in establishing and sustaining trees in high density cities.  It includes separate studies on the production, planting, arboricultural maintenance, protection of trees and transplanting of street trees in high density urban environments, and addresses the historical perspective, the underlying arboricultural science of trees in the street and the development of best practice standards.  Although focused on Hong Kong, the outputs of the studies are directly relevant to many high density cities in tropical and sub-tropical climates. 

Outcomes and outputs:

Academic publications

Pryor, M. and Watson, G.  Mature Tree Transplanting: Science Supports Best Management Practice.  (in print) Arboricultural Journal.  DOI: 10.1080/03071375.2016.1157401.

Pryor, M., Street Tree Planting in Hong Kong in the Early Colonial Period (1842-98). Journal of the Royal Asiatic Society Hong Kong Branch. Vol 55.

Pryor, M. A tree preservation ordinance for Hong Kong: An historical note. Yuan Lin 2015.

Pryor, M. and Li, W. (2015). Aerial roots of Ficus microcarpa.  Yuan Lin, Journal of the Hong Kong Institute of Landscape Architects.

Conference papers and other publications

Pryor, M. (2014).  Extreme Arboriculture: Lessons from moving big trees.  In proceedings of Trees People and the Built Environment II conference p196-209. Institute of Chartered Foresters. Birmingham UK.   (April 2015) <>

Pryor, M.  (2014) The challenge of planting trees on slopes in Hong Kong.  7th Annual International Arboriculture Summit – Hong Kong. (November 2014)

Pryor, M. Demystifying Tree Transplanting.  In proceedings of IASHK Seminar Hong Kong,  (November 2012).

Pryor, M. (2012).  Street Tree Planting (Ch.7) and Street Tree Establishment & Maintenance (CH.8).  In Development Bureau HKSAR, Comprehensive Street Tree Management Plan for Hong Kong (confidential report).

Pryor, M.  Model Specification for tree transplanting and related works in Hong Kong. (2015) Open source publication on research website

Invited lectures

  • Pryor, M. Transplanting mature trees.  Technical Seminar, University of Hong Kong.  (17 October 2015).
  • Pryor, M. Urban Tree Transplanting in Hong Kong.  Chinese University of Hong Kong Seminar on Urban Greenery in Hong Kong.  (12 July 2014).
  • Pryor, M. Demystifying Tree Transplanting.  In proceedings International Arboricultural Society Hong Kong Conference 2010, Hong Kong.  (November 2010)


Applied Research

Invited technical expert for the following high profile tree protection projects.  All work was peer-reviewed by professional and academic experts.

  • Kennedy Town Station – Protection of stonewall trees at Forbes Street (for MTRC). (2010-2015).
  • MTRC Express Rail Link (XRL) – Tree transplanting and tree protection, Contract 801. (2010-17).
  • Widening of Castle Peak Road: Castle Peak Bay – Tree transplanting and tree protection, Highways Department, Contract CE17/2013(HY).
  • Wanchai Bypass, Phase II – Independent Technical Review of Victoria Park Mature Tree Transplanting, for Highways Department, Contract No. HY/2009/19. (2013-14). Central Reclamation Ph.III – Independent Technical Review of Koelreuteria paniculata Trees along Roads P2 and D6, for Highways Department, Contract No. HK12/02 (2013-14).
  • Kowloon Park / Haiphong Road Old & Valuable Trees – Technical Specialist (for LCSD) (2013-14)
  • Technical advisor to HKILA & HKIE Joint Task Force on Wall-Tree Management (Aug 2015 – Mar 2016)


Anticipated Further Outputs

  • Pryor, M. and Sarkar, C. Responses to transplanting of three species of street trees.   (Under revision for Forestry: An International Journal of Forest Research).
  • Tree transplanting research website.


Quotation / endorsement:

“The tree which moves some to tears of joy is in the eyes of others only a green thing that stands in the way. Some see Nature all ridicule and deformity, and some scarce see Nature at all. But to the eyes of the man of imagination, Nature is Imagination itself.”


William Blake, 1799, The Letters


Awards for this research:

  • Landscape Institute UK Award 2014 : Winner – Landscape Policy & Research category (, for “A Comprehensive Street Tree Management Plan for Hong Kong” undertaken by Urbis Limited for Development Bureau (role, contributing author / team member)
  • HKILA Landscape Awards 2014 (Silver Medal, Landscape Management Category), for “A Comprehensive Street Tree Management Plan for Hong Kong” undertaken by Urbis Limited for Development Bureau (role, contributing author / team member)
  • HKILA Landscape Awards 2014 (Silver Medal, Research Category), for “Research into Tree Transplanting in Hong Kong”






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