Copyright Natural Habitats 2016

Landscape Success on Auckland Motorways

Landscape Success on Auckland Motorways


As both motorists and landscape professionals we have a keen interest in understanding the facts that lead to some motorway landscape projects thriving, while others fail miserably. Those that have failed represent lost opportunities to improve motorway user experience, as well as millions of dollars of wasted tax payer money.

After running a case study based on seven newer-style Auckland motorway projects we found three of the seven investigated projects failed (42%), due to insufficient coverage. Success was judged on canopy closure and therefore the sustainability of the plantings. Canopy closure minimises weed invasion, lowers maintenance need & cost and allows the planting, rather than weeds, to thrive.

When studying the seven sites we compared:

1. Date completed
2. Planting type
3. Health of planting
4. Soil type
5. Mulch
6. Weed invasion
7. Whether the landscape met with the NZTA base criteria for achieving practical completion, i.e. at least 80% cover

And we considered various contributing factors that may impact on project’s success:

1. Landscape designer / architect (all were ‘Landscape Architects”) and their plant selection
2. Plant supplier / grower
3. Soil / media placed on the job for plants to be planted into
4. Head contractor for the project
5. Landscape contractor

To our surprise, soil did not seem to be a factor of success or failure, as on all sites it was well below what a horticultural or NZTA spec requires. Only one project had the specified topsoil (and the plants are thriving). When topsoil is excluded, our study suggests the two variables that were common in the failures are: Head Contractor and their Installation Landscape Contractor.

The same landscape architects were involved in both successful and failed installations and the bulk of the plants came from the same major supplier.

We cannot comment on project management skills or corporate project philosophy, but do wonder if Head Contractors are forced, or force themselves, into only counting the immediate cost in a tender, rather than the whole life cost. Is this fixation on ‘cheapest is best’ helping to produce the cost of failure we all, as taxpayers, must now bear?

Head Contractors play a role in the success or failure. Their view on value and selection standards controls this, as does their landscape contractor selection and the finished planting standard of acceptance, (often against the NZTA standard).

The Landscape Contractor who installs the landscape seems to be the major variable in success / failure. The recent recession has certainly exaggerated the flight to cheap and the cheapest price cannot include adequate planting practices or maintenance.

Natural Habitats other observation is that NZTA standards are not followed or applied on the of failed projects by the Head Contractor or NZTA. For example, topsoil is not up to standard on most jobs and we suspect it is handled exactly like road aggregates, rather than a living thing. At least for roading aggregates, they have strict standards for supply, placement and performance and it’s tested. Topsoil is usually not. While most plants can survive this, better soil would allow them to flourish.

The 80% cover is often not attained yet this has been accepted. The failure of this standard allows shoddy practices to be accepted and places an unfair burden on the AMA or whoever must take it over, let alone the taxpayer who suffers the waste of money.

Even the ones that get to 80% cover – evolve. The initial “pioneer” plants are exactly that, pioneers. They establish, grow and die. In nature they would be replaced by the next stage of a forest’s development. In the highly modified, usually urban environment, the wild seed source is not available. Secondary planting is not planned or budgeted for, which allows weeds to establish.

Landscape is only ever a mere few percentage points of the total budget, yet it is the most visual experience on any motorway trip. Auckland is one of the world’s “weediest” cities and the result will be eventual loss to weed invasion.

At this point the older projects are almost assisted by less than optimal maintenance. “A stitch in time WILL save nine” in this case and must be programmed to be done, or a high monetary loss faced.

We suggest that given the laudable aspirations of NZTA for their projects and the need to consistently achieve even the basic landscape standards, there needs to be thought given to what is driving a 42% failure rate in this study. It represents millions of dollars of wasted money and countless more in lost opportunity.

Natural Habitats is New Zealand’s largest and leading integrated landscape company. They have been trusted to design, deliver and care for some of Australasia’s most iconic landscapes. In New Zealand, Natural Habitats are at the forefront of the movement towards green technology in architecture.

To find out more visit www.naturalhabitats.co.nz.

Note: The seven projects included in the study were:

1. Manukau Harbour Crossing (successful)
2. Northern Busway (successful)
3. Victoria Park Tunnel (successful)
4. Central Motorway Junction (successful)
5. Grafton Gully to Stanley St (now failing)
6. SH 16 (much failing)
7. SH 1-20 (failing)

Author: Graham Cleary, Director of Natural Habitats