You are currently browsing the tag archive for the ‘tree canopy’ tag.

Two dead street trees right next to each other in Marrickville – notable because they are beside each other.

My last post was about the NSW government’s ‘Five Million Trees’ initiative.  See –    The aim is to increase Sydney’s existing tree canopy from 16.8% to 40% over the next 12 years at a cost of $37.5 million over four years.

Fortune had it that I came across a long & detailed article from Scenario Journal titled, ‘How Many Trees Are Enough? Tree Death and the Urban Canopy’ written by Lara A. Roman.

The article looked at tree survival across US cities.  Research has found that, despite concentrated campaigns to increase the urban canopy in many major US cities, the canopy cover is actually declining. This is of major concern considering the extra pressure we have from increased development, a changing climate & its associated urban heat island impacts.

Three questions were asked –

  • “With major new planting campaigns, how many of those trees will survive for decades, reaching a mature size at which their environmental and socioeconomic benefits are greatest?
  • How many trees are enough – that is, how many need to be planted to make a lasting impact, and meet a city’s canopy cover goals?
  • What are the implications of future tree death for managing the urban forest, in terms of cycles of tree removal and replacement?”

“For street trees in New York City, eight to nine years after planting, 26.2% were dead.  For a yard tree give-away program in Sacramento,  five years after planting, 29.1% had died, on top of 15.1% that were never planted by residents.  For these yard and street tree examples, over a quarter of the trees planted died within the first five to nine years, and furthermore, for the tree give-away, some trees never made it into the ground.”                                                 

As part of their 5 Million Trees initiative the NSW government plans to give away 15,000 trees to people who are building homes in new land release areas in Western Sydney.  I wonder how many of these trees will actually be planted.  I don’t know about you, but I have bought plants from the nursery & left it too long before I put them into the ground.   One can realistically expect that high numbers of these giveaway trees will not be planted in western Sydney.  Will these be acknowledged, or will they just be written up as a successful addition to the urban canopy simply because they were given away?

The Inner West Council has given away trees for the past two National Tree Days & I applaud them for this.  It would be interesting to know whether Council has gathered information about how many of these trees made it into the ground & how many are still alive today?

The article notes that in the US there is very little in regards to monitoring & follow-up with tree planting campaigns & calls for a nationally coordinated monitoring network.

The author then cites the common belief that street trees live on average for only 7-years & a maximum of 13-years. Apparently, this belief was formed decades ago where a questionnaire was sent to urban foresters “asking the local experts to estimate the typical tree lifespans in their cities.”  The author describes this as “overly pessimistic.”

One only need to look around our own suburbs to know that there are plenty of streets with street trees that are 70-100 years of age.  Generally, these are QLD Brushbox or Fig trees.

A study to understand the change in the street tree population of West Oakland in the US looking at annual tree planting & tree deaths found that the annual mortality rate was 3.7%.   Most of the tree loss came from newly planted trees with a trunk of 7.6cms (3 inches).

“Extra vigilance during the establishment phase, in terms of maintenance and stewardship, might have the most payoff for ensuring planting survival, and thus achieving larger canopy objectives.”

“Planting a few hundred trees, or even a million, does not automatically translate into an increase in the overall tree population over the long-term. To increase population levels, the survival and planting rates have to out-weigh losses from tree death and removal, including both old and young individuals.”

I think this article brings up serious issues concerning increasing the urban forest.  I’ve noticed that street tree removals post Marrickville Council’s Tree Inventory meant that for at least 3-4 years the urban forest numbers stayed relatively the same.  With 1,590 streettrees to be removed from 2013, planting around 400 new trees a year meant that making up ground was slow.

I have noticed that a lot of street trees have been removed in the last couple of years.  Since Council does not report the removal of trees 5-metres or under & since 49% of our street trees were found to be 5-metres or under, we have no idea where street tree numbers are at now & no ability to calculate this ourselves.  The Tree Inventory was costly, so I doubt we will have a new one done for many years.

Increasing the canopy means not the number of trees planted, but the percentage of total ground area; for example, at 50% canopy cover, half of the total ground area is covered by the vertical projection of tree crowns.”  

This has an impact on the way Council prune street trees as well. Continuing to remove side branches that serve to make the tree canopy fuller & produce longer periods of shade is counterproductive – unless it is required for safety reasons like branches over the road affecting passing trucks as an example.  However, you only need to look at the street trees around you to know that many street trees are pruned to have no side branches.

Council’s policy of no tree branches 2.5-metres (8.2 feet) above a footpath pretty much ensures that the footpath will have no shade except for perhaps an hour when the sun is in the right position.

The Five Million Trees initiative may result in significant changes with tree planting & reporting.  It would be good if this information is available to the community should they be interested.  Hopefully, outdated ways to manage street trees get dumped & our urban landscape becomes green & flourishing.

A Marrickville streetscape – a good one because it has street trees 2 storeys tall.  Photo June 2016.


1.          The Cumberland Courier reported that Energy Australia is to spend $62 million installing high-voltage power lines between substations at Allambie Heights & Balgowlah to protect endangered tree communities at River Flat Eucalyptus Forest & Duffys Forest Ecological Community & to not damage historic Sloane Crescent Bridge.  This is a great thing they are doing.

showing the Optus cables clearance - extreme at this end of Renwick St Marrickville South. At the other end of this street the branches were pruned to & above the Optus cables

Pity about what Energy Australia did to the street trees at the Woolworths end of Renwick Street during ‘routine pruning’  last February.   People just looked at the trees with their mouth open.  As usual, the feeling was “the damage is done & there is nothing we can do about it.”

It is such as shame as we know they can do better.  See where just last February I complimented Energy Australia for the good pruning they did in Excelsior Parade.  Even Renwick Street has different pruning outcomes.  The lower end, towards Carrington Road, the street trees were moderately pruned. Some trees that had been almost destroyed during the previous pruning cycle 7-8 years ago were looked after this time.  Interestingly, Energy Australia workers did not clear branches below the Optus cables at this end of Renwick Street, whereas up the other end the Optus cables where given a huge clearance. The trees on the corner of Renwick & Excelsior had more than 2/3s of their canopy removed.

2.         Brisbane City Council announced they will plant 2 million trees across the city by 2012.  This is a fabulous initiative & the community can participate.

Their website says residents can request a street tree be planted & provides a list of suitable trees.  Brisbane City Council also say they plant trees which will not interfere with overhead powerlines & that street trees are classified as “valuable Council & community assets” & protected under the Natural Assets Local Law making it an offence to prune, interfere with or remove street trees.  Wonderful.

In another lovely initiative, Brisbane City Council has organised Tree Trail. Information & a map of 20 locations can be downloaded highlighting special & significant trees around the CBD.  I think this is a terrific idea & believe it would be a boon for tourism.  HTTP://

3.                 Hornsby Councillor Bruce Mills’ proposal to plant mature trees to create ‘instant boulevards’ was voted in during a March Council Meeting.  Residents need to request that their street become a tree-lined boulevard. Councillor Mills says this initiative will be “returning ratepayer funds in a way which adds to their property value.”

After pruning by Energy Australia, this tree on Renwick Street is a shadow of its former self

The Boulevard in Dulwich Hill is an excellent local example of a street loved because of its many, large street trees that cascade over the road.  Ask any real estate agent & they will tell you this street is sort after with buyers paying more to purchase property here because of the presence of these trees.

The following is a short, but relevant article about trees & property value in America.  Adelaide University has assessed the value of trees upwards to 25% of the property’s value in line with Australian property prices as they are more expensive than in the USA.

Personally, I would love it if our Council copied the ‘instant boulevard’ idea. Even planting more developed trees would be a step forward as these have a greater chance of surviving.  City of Sydney Council planted 200 litre root-ball 4 metre high Simon Poplars along & on the corner of side streets in Glebe Point Road  in 2009.   All these trees have survived & are growing well.  There positive impact was immediate & the area looks greener & prettier for it.

4.                 City of Sydney Greens Councillor Chris Harris wrote about a proposed cycleway in Johnstons Creek that he says will destroy wildlife habitat.  This new 2.5 meter wide cement path starts at Orphan Creek, an woodland & wildlife habitat area in Forest Lodge that was decimated for a similar path in 2009 despite enormous & organised community opposition.  What is also disturbing in this article is residents from Minogue Crescent who are directly affected by the new cycleway, were refused permission to address the Councillors during a Council Meeting who ‘voted in a block’ to deny them this opportunity.  I would have thought it a right.

5. The Daily Telegraph reported that State Forests NSW started woodchip logging in the Mumbulla & Murrah state forests on 29th March 2010 despite this being the last area in SE NSW where the threatened species Koala lives. A group of residents attempting to save the Koala habitat managed to stop logging by getting in the way of loggers.

This street tree in Renwick Street had a naturally round canopy. Before it was pruned early 2010, it looked something like the area shaded in yellow. It may have been taller

Koalas are listed as a threatened species & classified as ‘vulnerable.’ From the NSW state governments own web-site – A ‘vulnerable’ species is likely to become endangered unless the circumstances & factors threatening its survival or evolutionary development cease to operate. Yet, they are taking down forests where Koalas are known to live.  I just don’t understand this.

Everyone fell in love with the burnt Koala who was filmed drinking water given by a Fireman during last year’s Victorian bushfires, but we can’t rely on our government to save our national emblem.  For more information about this issue including how you can help, go to Nature Conservation Council of NSW

A while ago I found an interesting fact sheet from July 2003 on street trees by Jane Edmanson for ABC’s Gardening Australia.  The fact sheet said: the use of Aerial Bundled Cables to put overhead wires through trees needs only a 600mm (just under 24 inches) pruning hole to meet requirements.  Otherwise, a 5 metre (16.4 feet) pruning hole is the norm, which results in very unsightly trees.

Energy Australia’s web-site states that the ‘vegetation safety clearance’ for overhead wires needs to be 1.5 metres (4 ft 9 in) around wires, meaning 1.5 metres either side of the wire and 3 metres (9 ft 8 in) in total.   In my locality, the wiring & pay TV cables take up around 1.5 – 1.8 metres (6 feet) of space on the power pole.  Add this to the safety clearance requirement & it is now a minimum 4.5 metres (14 feet 7 inches) pruning hole.


Energy Australia also say they have to trim branches back to the nearest growth point located outside the limit of clearance required.  Therefore, if the growth point of a branch is 2 metres away from the outside limit of clearance, the branch is actually cut back 3.5 metres (11.4 ft). If the growth point is further away from the required clearance, the pruning hole is larger.


I wonder is this necessary? Gardening Australia didn’t think so way back in 2003.  Currently the charges for AB Cables are prohibitive for Council.  However, if Energy Australia lowered the fees for AB Cabling, they would save money on the constant pruning they are required to do & it would all balance out in the long run.



Down to the nearest growth point

Far too many of our street trees look ugly, lob-sided, stumpy or flat like an umbrella. Just when they are starting to look semi-respectable, Energy Australia returns & the cycle is repeated.  Then Council identifies trees that have become too ugly or sick after pruning & removes them.  While I applaud Council for doing this, I feel sad that our LGA loses its large trees & the history of those trees that were planted when our suburbs were being built.  I am concerned the tree pruning practices of Energy Australia radically changes the look, feel & skyline of our area.  There has to be a better way.


Michael Easton, who runs Marrickville Bush Pockets, recently wrote a comment on this site. We should be surveying for areas where large trees can be planted & where powerlines aren’t a problem. There are plenty around once you start looking.

I agree.  In the About page, I wrote I wished new tall growing trees will stop being planted under electricity cables & new tall growing trees will be planted in the open spaces between cables.  Michael takes it a step further by saying that Marrickville LGA should be surveyed.  Can you do this Marrickville Council?  Will you cut holes in cement, build garden islands, plant tall growing trees in these areas & allow them to grow a normal canopy?  It would make a huge difference.

I am not pro-tree removal, but many of the street trees in Marrickville LGA will never be allowed to grow normally & look beautiful.  Is the solution a combination of my dream & Michael’s suggestion?  Imagine if Council does slow phased removal for those trees that have really been knocked around & will always look bad & replaced them with short stature trees so there was no need for Energy Australia to prune them.  Imagine if Council planted tall stature trees on the opposite side of the road where there are no power lines & in the empty spaces between where the power lines connect to houses or unit blocks.

Depending on how it was done & the species planted, the streets could look much better, far better than they do now.  The many empty spaces would be filled with green.  The trees & wildlife would be better off & so would the community.

This would be a long-term project, particularly as Marrickville Council only plants trees for a short period each year.  It would be even better if the community could be involved in deciding which trees are too far gone & what species should be replanted.  Streets could have themes.

I recognize there are many potential problems – disagreement with Council about which trees should be removed, what constitutes a suitable time frame for phased removal, what species to plant & resistance from those in the community who would rather no street trees were planted.  I have never seen my role in SOT as having the answers.  Council are the experts.  The community can suggest & Council can choose to explore these suggestions.

I have added 2 pages to this site.  ‘Nominate a Space’ where you can suggest sites where one or more medium to tall stature trees can be planted & ‘Nominate a Tree’ where you can add a tree you think should be included in a Significant Tree Register.  Marrickville Council does not have one at present, but they might establish one in the future.  Perhaps if there are enough suggestions, Marrickville Council will become interested & decide to do as we ask.  They are always seeking contribution from the community. This is just another way.



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