STEM, the Standard Tree Evaluation Method: what the Notable Trees Trust, NZQA and councils' thresholds say

This page reports what the official source says. It is not legal advice: ask the office named here. It describes the Standard Tree Evaluation Method (STEM) as the New Zealand Notable Trees Trust, the Royal New Zealand Institute of Horticulture (RNZIH) and the New Zealand Qualifications Authority (NZQA) word it, on pages read on October 9, 2026. It does not score any tree. Other published methods are set side by side on the page comparing CAVAT and i-Tree Eco.

What STEM is

The Trust describes STEM as a heritage tree evaluation method first published in September 1996 by Ron Flook, as STEM: A Standard Tree Evaluation Method (Nelson, ISBN 0-437-04039-5). It says the method quickly became the most widespread way of evaluating heritage and notable trees for district plans in New Zealand and is used by the majority of local authorities that schedule notable and historic trees. The Trust became the copyright holder in August 2012, with the Flook family's agreement, and holds the trademarks on both the full name and the short form. STEM scores can be entered on records for trees on the New Zealand Tree Register, and copies of the manual are sold by the Trust.

The RNZIH reproduces Ron Flook's 1996 article from its Garden Journal. It says STEM followed the Institute's own tree evaluation method of 1988 and the 1994 publication of a list of more than 2,000 registered notable trees, that a fifth draft was launched publicly at the First NZ Tree Symposium in Rotorua in August 1994, and that field trials covered over 600 trees. The article says the consensus was that STEM is uncomplicated by formulae or multiplications that other systems use, and that it is able to set a monetary value based on a tree's evaluated quality, with a conservative approach called essential. A web note on the page says more than 35 councils use it.

What NZQA says about it

NZQA unit standard 32780 is titled "Describe amenity tree evaluation criteria and apply the Standard Tree Evaluation Method". It is at level 5, worth 4 credits, classified under Horticulture, Arboriculture, and was registered on June 24, 2021 with a planned review date of December 31, 2026. A person credited with it can describe tree evaluation criteria and the three components of STEM and apply STEM in evaluations. The range statement asks for evidence of at least 10 evaluations using STEM and 10 using one other system.

Score thresholds councils use

The Trust's threshold table, updated July 1, 2025, says there is no set national threshold, because each local authority decides which trees are significant in its own context. It warns that direct comparison of scores between councils is not advised, because tree stock differs by region, assessors vary, and some councils have added criteria that inflate scores. The figures below are points as the Trust lists them. Entries it marks proposed or under review are shown as such.

Council	Threshold listed by the Trust
Carterton	150 points
Dunedin	145 points
Far North	Under review (130 points proposed)
Gisborne	120 points (proposed)
Gore	100 points or above
Hamilton	130 to reassess existing scheduled trees, 120 for new street or reserve trees to be scheduled
Hastings	160 points, or a minimum of 50 years old and including a notable attribute
Hauraki	87 points
Horowhenua	150 points
Kaipara	150, under review
Kapiti	140 points
Lower Hutt	120 points
Manawatu	150 points
Marlborough	150 points, or a tree with a local notable attribute
Masterton	150 points or more (proposed)
Matamata-Piako	140 points
Napier	180 points
Nelson	100 points
Otorohanga	160 points
Palmerston North	160 points (adapted STEM)
Porirua	120 points
Queenstown-Lakes	120 points
Rangitikei	Listed as unknown
Rotorua Lakes	140 points
Selwyn	130 points
South Taranaki	130 points for native trees, 150 points for exotics
South Wairarapa	110 points (proposed)
South Waikato	Listed as unknown
Tasman	120 to 149 points Category C, 150 to 190 points Category B, over 190 Category A
Taupo	110 points for amenity trees, 130 points for notable trees
Tauranga	130 points
Thames-Coromandel	170 points
Timaru	125 points
Upper Hutt	100 points
Waikato	160 points
Waimakariri	130 points
Waipa	110 points
Waitaki	130 points (proposed)
Wellington	110 points, under review
Western Bay of Plenty	120 points
Whakatane	135 points
Whanganui	150 points. Trees under 150 may be protected if they have value to the community
Whangarei	100 points

Where it sits among other methods

The contents page of MIS506, the Minimum Industry Standard for Tree Valuation published by Arboriculture Australia and the New Zealand Arboricultural Association, lists STEM with Burnley, City of Melbourne, the Council of Tree and Landscape Appraisers method, i-Tree Eco and Thyer as selected methods, with context, method and an example for STEM.