One Tree Hill summit project
New tree planting proposal
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3.0 Site assessment
3.2 Planting methodology
Environmental and physical constraints make the summit of Maungakiekie an extremely challenging site to plant and establish a tree. Site management policies,
cultural and landscape elements, and the physical characteristics of the site have been considered in the development of the proposed planting design options.
The following issues have been identified as being critical to the successful establishment of the One Tree Hill summit tree.
3.2.1 Potential effects on the site
Site protection and minimising adverse effects on the site are of primary importance. The site constraints regarding the extent of excavations and use of
machinery limit planting methodology options and the maximum size of a tree that can be transplanted.
The introduction of artificial structures such as shelter, a protective cage, and support for the new tree should be sympathetic with site characteristics and
durable. Also, the use of a mulch needs to be carefully considered as not to have an adverse effect upon adjacent archaeological features such as the kumara
pits.
3.2.2 Environmental and tree establishment issues
The exposed site conditions make successful tree establishment on the summit of One Tree Hill (Maungakiekie) difficult. Several previous attempts to plant trees
on the summit are known to have failed. It is critical that the physiological requirements of the new tree are considered to ensure successful tree establishment
and survival.
Thus, the following practices should apply.
- Selection of tree species that are tolerant of the site conditions.
- Appropriate site preparation, for the site conditions and the selected tree(s).
- Using appropriate planting techniques and arboricultural practices.
- Implementing an after-care maintenance programme that is appropriate for the site conditions and the selected tree(s).
Results from research show that small grade trees are less prone to transplanting shock and stress, and are more likely to establish successfully than
semi-mature trees.
This is due to smaller surface areas of tree roots and foliage, resulting in lower rates of evapo-transpiration and subsequently less stress due to water loss.
Also, semi-mature transplants are generally less vigorous than small grade trees because of the ratio of rootball to mass of tree is less and the tree needs to
expend more energy to replace root mass during establishment.
The inclusion of imported, and appropriate, soil into the planting site will need to be an initial consideration at time of planting.
Also, attempting to establish a tree without shelter, irrigation and after-care maintenance is not expected to be successful.
The shelter requirements of a newly planted tree are a critical consideration in order to protect from the elements. Support will also be required for the new
tree until the root system is established.
There is currently no water supply at the summit other than rainfall. Given the archaeological issues relating to excavation, it may be difficult to establish
a water source that will not be damaging to the site or easily damaged (e.g. vandalism, stock, etc). Therefore, manual irrigation is likely to be the preferred
method for watering during the trees initial establishment period.
The application of mulch onto the planting site is an initial consideration at time of planting.
Thereafter, until the planting has become established, these factors will all need to be incorporated into a maintenance programme. The maintenance and
management of the planting once established will require an ongoing commitment and will need to be consistent with the objectives of the planting proposal.
Potential growth rate and tree form
The immediate and longer-term visual effects of the planting are important regarding compliance with Management Plan policies, and meeting landscape design
objectives.
The visual appearance of the site has been considerably altered by the recent removal of the pine tree, and it is expected to take many decades for a new tree
to become significant in the landscape regardless of its size when planted.
Therefore in considering the most appropriate method for planting the summit, and acknowledging the site constraints, sustainability of growth and ultimate
selection of a singular specimen tree over time are considered.
A comparison of the expected growth rates of both pohutukawa and totara, of different size and planted in different designs, are graphically illustrated in
Appendix C
Single vs multiple planting
Of all the options originally assessed at a conceptual stage of design, two remain open for choice.
A single tree planting is as stated but species and size of tree could be variable given the site constraints.
A multiple planting has variations but generally size of tree is limited to smaller trees but the number of species could be more than single.
