Christchurch City Council
Greenspace Unit
Memorandum
Date: 21.02.2006
From: Dieter Steinegg (Tree Offiicer)
To: Ed Delilla (Project Manager Streets Capital Programme)
Dennis Preston (Design Leader)
Tree Condition Survey St. James Avenue
summary
Over maturity, structural decline, and diseases, makes the replacement of 48 trees in St. James Avenue a high priority. It is of vital importance to initiate a tree replacement programme to prevent the accumulation of declining trees. Proactive management decisions are needed to prevent loss of amenity value and prevent costly and complicated tree replacement in the future.
Introduction:
Following our site meeting on 07.02.2006 in regard to the proposed kerb & channel renewal, I inspected 60 trees in St. James Avenue positioned in the berms between Dalriada Street and Harewood Road or house number 51-138.
The purple plums were planted from 1935 onwards; the mature scarlet oaks were planted in 1945 to commemorate the fallen in World War II 1939-1945. The Avenue is also known as the ‘Papanui Memorial Avenue’.
The collection in this particular section of the avenue is made up of 40 scarlet oaks (Quercus coccinia)11 pin oaks (Quercus palustris) and 9 purple plums (Prunus nigra ‘Pissardii) of various sizes, ages and condition.
Previous maintenance attempts to raise the canopies of the trees in the more mature part of the collection between house number 83-138 to a required 4.5 metres above the carriage way have not been entirely successful. Some branches reach into the carriage way below the required standard and show numerous wounds due to collisions with high canopy vehicles.
Findings: Twenty-eight or 46.66% of all trees appear in ‘Poor’ condition with a sustainable life expectancy of 0-5 years.
Twenty or 33.33 % are classed as in ‘Fair’ condition with a life expectancy of 10-15 years.
Twelve or 20 % of the trees are classed as in ‘Good’ condition with a life expectancy of 20-80 years.
Recommendation: For health and safety reason, it is not advisable to wait for trees in a high target area to die completely before they are replaced. This approach would also lead to loss of design integrity and amenity value over a longer period of time. It is therefore advisable to look at a sustainable life expectancy and the need to provide for the future, and renew an even aged, aging tree population, as experienced in many streets around Christchurch.
The trees in St. James Avenue have been evaluated on an individual basis. In some instances trees classed as in fair condition are located close to trees in poor condition, under such circumstances it is recommended to replace the remainder to prevent malfunction due to sudden exposure like branch failure and other associated problems.
A number of young and semi-mature trees between house number 25 and 78 are in need of urgent attention due branches lower than 2.5 metres above the footpath (eye hazard). There is also evidence at house number 25 that perhaps residents attempted to prune trees away from the carriageway and parking bays.
Due to ‘over-planting’ in some areas it is recommended to reconsider the position of some specimens and transplant trees from house number 29, 39,47, 69, 73a, into more suitable areas.
A regular tree maintenance programme is urgently required to assure the overall safety and success of this unique tree planting of outstanding historical significance.
Conclusion: Trees like all living organisms have a natural finite life expectancy. The situation of removing and replacing over mature and hazardous trees has to be faced frequently. It is therefore important that if any plant collection is to survive, a constant maintenance and replanting process takes place.
A new generation of high quality trees can be trained above and below ground in such a way that traffic safety, power line and boundary issues are kept to a minimum.
The relatively short sustainable life expectancy of 0-15 years in some 82.% of all trees would lean it self to a complete tree replacement programme in the mature part of the collection between house number 83-138 and the replacement of 5 over-mature purple plums located opposite property number 55, 59, 63, 72, and 76.
I hope these findings will help you in your consultation and planning processes
For more information please contact the author of this report at the above extension
Dieter Steinegg
Tree Officer