Heat stress and tree death won’t daunt Northbourne’s tree planting

Genevieve Jacobs 25 January 2019 131

An artists’ impression of how the eucalyptus mannifera will look surrounding the light rail route. File photo.

Despite death, decline and heat stress, Transport Canberra senior management say they remain confident that the eucalyptus mannifera specimens planted along Northbourne Avenue are the right choice for the light rail zone and will eventually thrive.

That claim has been disputed by an expert regional silviculturist who remains adamant that the trees are “doomed” and that planting advanced trees to satisfy public expectations demonstrates “a very basic lack of knowledge”.

Marcus Sainsbury, who is the senior manager design planning and environment for Transport Canberra wouldn’t put an exact number on the trees that are dying or likely to die along the Northbourne alignment although he conceded the long run of extremely high temperatures had been very stressful for the newly planted four-metre trees.

“There are two categories – the ones that are in permanent decline and ones that are under stress,” he said. “It’s fair to say that in general terms the industry would expect a 5 per cent loss of mature trees planted, and we’re confident that we are under that at the moment.

“Clearly some of the trees have died and by the same token, some of the trees under stress have made a recovery. We are monitoring the ones under stress and seeing how they go, maintaining a watering regime for the stressed trees over the past few weeks.”

Paradoxically, heavy surface watering can create shallow root systems and unsustainable growth because the trees aren’t anchored deeply. Mr Sainsbury says this is a fair observation but believes that the “bespoke” planting environment installed for each tree will solve any problems.

“We’ve used 30 cubic metres of growing medium for each tree, and that level of soil preparation was never undertaken in the past. Previous trees were sitting on a clay pan which meant that the roots spread out in shallow systems. But the manniferas have provision for deep-root watering, where the water is channelled down to the base of the tree pit to promote root growth.”

Mr Sainsbury says the growing environment should also prevent compression from construction traffic, parrying the suggestion that it’s a compromise to plant them out at this size rather than planting smaller trees.

It’s there that he differs considerably from independent silviculturist Peter Marshall, who runs TerraPreta truffles at Braidwood and has over 40 years of forestry experience. He believes more trees are doomed because of “this concept of growing a tree to be long and thin and whippy and putting it in to create an instant forest.

“It’s a construction zone with soil compaction and concrete in the soil so the PH will be very high from the leftover lime. The position is very exposed and there’s a massive swing in temperatures at ground level from day to night.

“Had they planted little dollar seedlings of the same species they would have grown a metre in every year, at an astonishingly lower cost. This nursery-grown stock is four metres tall now, but they’ll possibly die under the stress of exposure, while the tubestock would get there quickly, with a much better root architecture and stability.

“Where is the survey that says the public want tall saplings that then die? Have they made this up in their own heads?”

Marshall is also critical of the species choice, saying the eucalypts risk shedding limbs as a matter of course. “High-temperature limb breakage is an ecological adaptation. A water column in the trunk literally explodes and detaches itself, which creates a hollow nesting place for birds and animals, whose manure then fertilises the tree. That’s a great ecosystem adaptation, but a massive disadvantage in an urban environment.”

In stark contrast, the tree planting process is characterised as “careful and deliberate” by Marcus Sainsbury. “Back in May 2017, we established a landscape trial plot that replicated in exact detail the planting arrangements for Northbourne. We are not watering the trial plots trees at all now and the regime has shown that those trees are doing really well”

Peter Marshall argues that deciduous trees, perhaps Mexican oaks from a very similar climate but with a much stronger root and branch structure would have been a better choice amidst Canberra’s magnificent tapestry of trees. But Marcus Sainsbury is adamant that the manniferas are the right choice and will thrive.

Do you think mature eucalypts were the right choice for the Northbourne corridor?

 


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131 Responses to Heat stress and tree death won’t daunt Northbourne’s tree planting
Steve Quasi Hoppitt Steve Quasi Hoppitt 1:35 pm 29 Jan 19

Wrong choice. We want....a shrubbery! :)

Ricky Toms Ricky Toms 1:28 pm 29 Jan 19

No!! I reckon Prunus serrulata !! Can you imagine driving in to Canberra in spring for Floriade and the corridor is full of cherry blossoms 🌸

    Janet Ilchef Janet Ilchef 3:03 pm 29 Jan 19

    Ricky Toms I think pin oaks. No dropping limbs and heaps of shade

    David Brown David Brown 3:06 pm 29 Jan 19

    Ricky Toms But a little bare in winter.

    Ricky Toms Ricky Toms 3:59 pm 29 Jan 19

    Well pruned they look ok bare... and it’s only for 12 weeks

Amanda Evans Amanda Evans 1:26 pm 29 Jan 19

These trees were too advanced to settle in properly and thrive especially after being spoilt at Yarralumla Nursery then put out into such an exposed environment. I think it's fair to say they were planted out at the wrong time of the year. They should have waited until Autumn, after they had addressed the soil needs and then planted seedlings just as Peter Marshall has said.

Eucs don't grow well from advanced stock anyway and will undoubtedly fail. My question is why didn't we have a graduated mix of tree species which changed as they got closer to the city? thereby responding to the tree colour schemes which exist there already.

Also deciduous trees are far more suitable where people need to wait for the train. It's going to be very cold under those eucs in winter.

    Tony Williamson Tony Williamson 5:27 pm 29 Jan 19

    Eucalypts are not deciduous like most of the trees in town

    Kir Rin Kir Rin 8:58 pm 29 Jan 19

    Tony Williamson that’s her point.

    Tora Dance Tora Dance 9:09 pm 29 Jan 19

    Amanda I think you need to apply for a job with act gov stat! You have nailed this! 👏👏 I’m so impressed!

    Emilia Roberts Emilia Roberts 2:50 am 30 Jan 19

    Amanda Evans yep just went out to Yarralumla Nursery to get my free plants (I've moved into a newly built house) and was strongly advised by staff to wait until Autumn as the summer conditions are too harsh to plant. I'm sure they told the ACT government this too.

Ben Roberts Ben Roberts 1:23 pm 29 Jan 19

No, especially since the fully mature ones that were removed were piss weak and kept uprooting during storms and dropping branches in the heat anyway. Why plant more?

Colin Wilson Colin Wilson 1:22 pm 29 Jan 19

Light rail. An obscene waste of taxpayers money. (Just my 2 cents)

Stephen Esdaile Stephen Esdaile 1:19 pm 29 Jan 19

and they'll stubbornly keep replacing them with more mature gums at great expense to the Canberra rate payer...

Annie Andcooper Pike Annie Andcooper Pike 1:16 pm 29 Jan 19

Low level native shrubs far better choice than limb dropping trees onto power lines.

    David Brown David Brown 3:10 pm 29 Jan 19

    Annie Andcooper Pike Then there would have been a bare concrete corridor between rows of termite mounds. What a great entry to Canberra.

Imogen Ebsworth Imogen Ebsworth 1:14 pm 29 Jan 19

Robyn has there ever been a more canberra dispute

Tarz Lam Tarz Lam 1:10 pm 29 Jan 19

Would it be so hard to send a tanker out to water them once a week? The government doesn't seem to understand that all new plants need water whilst their root systems establish.

    Kate Carey Kate Carey 1:36 pm 29 Jan 19

    Tarz Lam there is an extensive underground watering system in place.

    Marc Edwards Marc Edwards 1:42 pm 29 Jan 19

    Peter Kelly I wouldn’t say they have been watering the trees, they slowly drive up the road with a spray bar, great for grass, trees need deep watering, I have been watching this since planting started. And the tree people I work with all stated that they would be surprised if 50% or more died.

    Tarz Lam Tarz Lam 2:00 pm 29 Jan 19

    The advanced trees they planted at Whitlam on Coppins Crossing road are not doing well either. It must be the exposure stress if the trees are being watered. I live in the suburb of Coombs and saw the suburb develop. Trees were rarely watered (I was a stay at home parent at the time) and there were many losses.

    David Brown David Brown 3:08 pm 29 Jan 19

    Tarz Lam Barr’s government doesn’t understand a lot of things, especially the community.

    Tarz Lam Tarz Lam 6:17 pm 29 Jan 19

    The few tankers I have seen in my area have involved a worker getting out and putting a hose on the tree. I think this is an acceptable method of watering.

    Ashley Wright Ashley Wright 8:50 pm 29 Jan 19

    Tarz Lam they have had the tree water people out too. They hose water directly into the pipes you can see next to each of the trees.

Les Eite Les Eite 1:10 pm 29 Jan 19

Wrong trees

Dying dropping limbs so what happens when they fall on cars or even worse on the tracks

    Sandi Ell Sandi Ell 3:24 pm 29 Jan 19

    Les Eite thought exactly the same thing. And what about tree roots lifting up the rails? Makes no sense.

    Ashley Wright Ashley Wright 9:12 pm 29 Jan 19

    Les Eite what happens when the trees that already line many roads road drop limbs?

    And no chance the roots lifting the rails. The tracks are in a deep reinforced concrete slab. And again plenty of trees near roads and the roads are not popping up all over the place. No doubt someone will provide few isolated examples to prove me wrong.

    Jorge Garcia Jorge Garcia 9:52 pm 29 Jan 19

    Ashley Wright no one can prove you wrong because you are right. All trees have advantages and disadvantages Mannifera have an undeserved reputation for dropping branches and killing people etc... The reality is that they grow up to be magnificent tall trees with a white trunk bright green foliage and an interesting branch structure. They support native birds and other creatures too.

    Les Eite Les Eite 10:12 am 30 Jan 19

    Ashley Wright where did I say roots will damage tracks. Those trees are fantastic but just not where major infrastructure is and very high power they are a fire hazard messy nothing grows under them just look at Anthony Rolfe drive dead bark limbs on the ground just waiting for a spark. I say wrong choice of tree

    Ashley Wright Ashley Wright 11:40 am 30 Jan 19

    Sandi said it.

    And there is no problem with very high power as you so put it. The power is actually considered by electrical standards to be low voltage. The overhead is energised at 750v DC, low voltage is anything under 1500v DV or 1000v AC. It is high current, but of course anything modern like that has safety mechanisms to cut power if there is an issue. Only need to look at the high voltage (25Kv + AC) lines that came down in Sydney at the weekend.

    Basically it is all manageable and no need for chicken little to say the sky is falling.

Sue Skinner Sue Skinner 1:01 pm 29 Jan 19

They're called Brittle Gums.

Donna Venables Donna Venables 12:56 pm 29 Jan 19

Nope. Dropping limbs. Clogging storm water drains with roots. Wrong choice completely

    Nate Jennings Nate Jennings 1:00 pm 29 Jan 19

    Donna Venables you might want to read up on the trees they used and what treatment the root systems have. Research before posting.

Jenny Gordon Avery Jenny Gordon Avery 12:50 pm 29 Jan 19

These type of trees belong out in the bush, not as single line of trees in a high traffic area in suburbia. Limbs dropping is just one concern.

Janet Mulgrue Janet Mulgrue 12:47 pm 29 Jan 19

should have stuck with the old entrance to Canberra instead of creating a white elephant

Toni Isaacson Toni Isaacson 12:44 pm 29 Jan 19

Still grieving the loss of the old ones.

    Jorge Garcia Jorge Garcia 10:38 pm 29 Jan 19

    I have to say that I don't understand why they couldn't work around the old trees. But then I look at any construction site and the destruction of trees and the disruption and contamination of nearby properties, nature strips and nature reserves beggars belief.

    Peter Kelley Peter Kelley 11:47 am 01 Feb 19

    A lot of the old trees had already died and more were on the way out - they were the wrong species for the job. Given the chance to start afresh you would think that they would get it right.

David Melville Rowlands David Melville Rowlands 12:42 pm 29 Jan 19

Younger eucalypts might have more chance, but eucalypts are definitely my preference for the main road into the national capital city.

    Jorge Garcia Jorge Garcia 8:55 pm 29 Jan 19

    David Melville Rowlands you are a breath of fresh air in an atmosphere full of bitter stale air... Eucalyptus Mannifera grow up to be magnificed tall white trunked trees with bright green foliage and they support native birds and other creatures. The right time to plant a tree is ten years ago so established trees are a great idea.... And my understanding is that these trees were raised to have a deep root ball to give them a great start. Dropping branches are not a problem when the trees are well looked after as these trees no doubt will. Definitely a great idea.

Michele Gorman Michele Gorman 12:35 pm 29 Jan 19

If they were grown locally they may have had a chance but it has been extreme heat. There aren't too many dead ones considering.

    Cass Proudfoot Cass Proudfoot 1:25 pm 29 Jan 19

    Terrible weather for anything to be planted out.

    Amanda Evans Amanda Evans 1:27 pm 29 Jan 19

    Michele Gorman they were grown at Yarralumla Nursery.

    Michele Gorman Michele Gorman 1:39 pm 29 Jan 19

    Amanda Evans I had a feeling they might have been. As Cass says above the weather hasnt been great for new plantings.

    Margaret Freemantle Margaret Freemantle 6:40 pm 29 Jan 19

    the media advised that the trees came from interstate. they were initially planted poorly when it was cool -why wasnt the planting of the trees left until the light rail was up and running give the poor trees a chance??!!

Arjay Arjay 8:43 am 29 Jan 19

The new eucalypts on Flemington Road seem to be doing pretty well. Mind you, they probably benefitted from not being planted in 40+ degree heat.

Grail Grail 8:28 am 29 Jan 19

You missed some details, such as how planting seedlings will help deal with soil compaction and pH.

The concerns about compaction were addressed in the answers provided in the article. I wonder what was left out in the editing process?

I will leave it to the experts: the project team have prepared a plot to trial the saplings and those are doing well, so let’s make an assumption that the plots are actually representative of the rail-side plantings and the team have it under control.

Capital Retro Capital Retro 8:22 am 29 Jan 19

That “artist’s impression” conveys a somewhat prophetic message given that there are no wires on the poles which then leaves them as crucifixes.

A graveyard for a failed tram project perhaps?

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