Importing new trees

1. Carefully select the species. Is the tree going to grow to an appropriate size to accommodate the available space? Do you have sufficient root volume for the chosen tree to grow and mature in? Does the species have any bad habits (i.e. excessive leaf litter, fruit, allergenic flower production, surface orientated roots, etc)? Will the species tolerate local environmental and soil conditions? What level of winter sun or filtered light is required under or around the tree, in particular on the south side?

2. Choose your stock wisely. There is often a need for expediency in the establishment of the urban landscapes. This often results in using larger tree stock planted at denser spacing. This has impacts on the tree species available, i.e. a limited palette of tree species, and can also result in poor tree establishment, performance and increased management requirements. The larger a tree is at the time of planting, the longer it will take to recover from transplant shock and establish in the landscape. Generally speaking, the time it takes to recover from transplanting is between 6 - 12 months per 25 mm of trunk diameter. It is estimated to take a transplanted tree approximately 9 months per 25 mm trunk diameter to recover in Melbourne. The larger the tree the more watering and after-care maintenance is required. The bigger the tree the more resources required to move it and install it. A tree with a trunk diameter between 75 mm to 100 mm is the optimum size to plant in the urban landscape. A transplanted tree of this size will establish quickly and more easily, is large enough to have an impact in the landscape and survive urban abuse. Money that could be used to purchase larger tress may be better used to create more optimum planting systems, for example improved soil conditions, drainage, irrigation, and surface treatments. In regard to transplanted trees; “…the first year they sleep, the second year they creep, and the third year they leap.” (Urban, 2008).

3. Other things to keep in mind include;

• Buy only trees that have an appropriate crown to root volume ratio. Big trees in small containers are most likely to fail.
• Look for trees that have good overall form, structure, foliar cover, have not been excessively pruned or are not too “leggy”.

4. Plant it well. Keep these points in mind;

• Plant during the cooler months (April - September). Planting during the warmer months will put additional stress upon the tree.
• Dig your hole 3 times the diameter of the root ball.
• Dig you hole no deeper that the depth of the root ball. Plant the tree proud (up to ? the depth of the root ball) if planting on poorly drained soils.
• Ensure that the soil dug to create the hole is tilled and broken up well before returning it to the hole. Generally, most landscape soils require no further amelioration other than water and air.
• Lightly tamp the soil in around the root ball ensuring no air pockets or gaps are left between the root ball and the surrounding landscape soil.
• Raise a berm or soil wall approximately 50 - 100 mm high around the edge of the root ball to direct water to the root ball.
• Mulch around the tree to the edge of the planting pit and to a depth of 75 - 100 mm ensuring that mulch over the root ball does not exceed 30 mm in depth.
• Water the tree in once it has been planted. This will help settle the soil and eliminate gaps or air pockets.

5. Look after it. After all this effort to select and plant a tree, to neglect it following this will result in disappointing growth and possible failure of the tree.

• Initially in the first month or two, water the tree with similar amounts and at similar frequencies as was done in the nursery gradually weaning the tree off the intensive irrigation program that is generally applied in the nursery. Always ask your nursery person how much water and how often it was applied before leaving with your tree.
• Once the tree is weaned, apply water weekly (twice weekly during hot and/or windy weather) at rates of 2 - 4 litres per centimetre of trunk calliper. The lower amount on poorly drained sites and the higher amount on free draining soils. Reduce water frequencies during cool wet weather.
• Maintain the mulch levels around the tree.
• Keep weeds out of the planting area.

Transplanting existing trees

1. Only select a tree or a palm that is healthy, vigorous and has good form and structure. Trees that do not fit this description are more likely to fail and will require more intensive management following transplant.
2. Only tackle something that you feel confident in moving otherwise hire a professional. Remember, landscape soils weigh between 1.7 and 2.2 tonne per cubic meter.
3. General rule of thumb is that the root ball diameter should be 8 - 10 centimetres for every centimetre of trunk calliper. Less for palms.
4. Carefully bind the root ball with hessian or similar material to ensure it does not fall apart during the moving process.
5. Plant and maintain as discussed earlier.

Download a pritable pdf here

City of Melbourne Experience

The City of Melbourne is internationally recognised for its tree-lined boulevards, parks and gardens. Trees beautify, define and soften landscapes and give scale to buildings in addition to providing shade and wildlife habitat. Trees are the most life enriching of all the types of vegetation used in the urban environment. They also contribute significantly to the maintenance of a healthy urban environment by trapping airborne pollutants and absorbing carbon dioxide.

The City of Melbourne manages approximately 60,000 trees including approximately 18,000 street trees.  Using the City’s ‘tree amenity valuation formula’ the total value of Melbourne’s trees is estimated to be over $600 million.  This asset is irreplaceable in the short term and the tree population requires close monitoring and management to ensure its continued good health.  Street trees also increase values of adjoining properties.

Melbourne has some of the most significant stands of mature elm trees remaining in the world following the destruction of many of the elm populations in the Northern Hemisphere by Dutch Elm Disease.  The elms lining the major boulevards of Victoria Parade and Royal Parade, along with the avenues of trees in the Fitzroy Gardens are registered as significant by the National Trust.

Of the City’s tree stock approximately 15,000 trees have grown in turf areas with regular irrigation. These include park trees and those grown in turf medians such as Royal Parade. Irrigation systems in the past have generally been designed to water the park surface, median or nature strip grass using manual or automatic surface sprinklers.  Although this method of watering keeps the grass green it is not efficient in watering trees as it encourages them to develop surface root systems.  Regardless of the species of trees and because of historical horticultural practices and the perception that water is a limitless commodity, trees have become dependent on regular surface watering and are less drought tolerant.  Many of the trees in the City of Melbourne have been stressed over recent years as a result of low soil moisture.

The severity of the problem has increased over the last couple of years. There are a number of factors that have contributed to this situation. Reduced rainfall in recent years with Melbourne experiencing 10 years of drought. Reduced application of supplementary water through changes to irrigation management initiated by water restrictions.  Reduced uptake of rainfall through increased hydrophobicity of soils.

In response to the drought and a move away from using turf sprays to irrigate trees the City of Melbourne has used a range of alternative ways to deliver water effectively to tree root systems and maintain soil moisture at levels to maintain trees in a healthy condition.

Soil moisture readings are taken in the City’s main gardens and boulevards in order to inform water application by monitoring the available water for the trees.  The City’s irrigation systems are being changed in order to ensure that the trees are provided with adequate water.

In a major move away from turf sprays over 160km of sub-surface drip line has been installed.  These systems are hooked up to existing infrastructure.  A fleet of water tankers and water-filled barriers have been brought in to supply water to drought stressed trees that cannot be adequately watered using the irrigation systems.  The water tankers are taking reclaimed water from the Royal Park Wetlands.

Recycled mulch has been placed under a large number of trees in parks that may be more susceptible to the dry conditions.

The sub-surface drip lines are considered to be a temporary measure and a more permanent and robust system has been developed to deliver water efficiently in a sustainable way. Street trees present particular challenges in terms of irrigation. These challenges include:

• Tree roots contained within median and street structures – limited water storage volume and limited catchment opportunity
• Tree root distribution highly variable and non symmetrical
• Access to root systems often limited by hard surfaces
• Tree roots in competition with turf roots for irrigation water
• Significant roots located deep within the soil profile – water needs to be delivered at depth
• Canopy interception of rainfall can be significant
• Compacted soils (low infiltration rates) - particularly on nature strips
• High peak daily water requirement
• Street trees are often high traffic and high maintenance areas
• Root disturbance and damage e.g. excavation reduce the effectiveness of parts of tree root systems
• The street trees may already be stressed due to disease or damage

A key consideration for the future watering of the trees will be the development of tree watering systems that will be permanently installed and supplied from a sustainable water source.

The following criteria were developed to establish the context within which a suitable tree watering technique could be identified.

Irrigation water effectively delivered to the tree root soil volume so that healthy growth can be maintained. Watering throughout the depth of the soil profile and lateral distribution are required.

• No overflow or surface flooding
• Minimum damage to existing roots through installation
• Installation technique not to impede root development
• Technique to work effectively in a range of soil types
• Plumbing of water delivery to allow regulated, low flow rate, delivery with minimum risk of blockage
• Installation technique to be flexible should large roots, services and/or rocks be encountered
• Installed technique to allow ground footprint area to be safely trafficked and not subject to subsidence. It should withstand loading that is expected from maintenance machinery and vehicles including trucks
• Robust construction of water delivery system
• Water delivery hardware to be accessible and protected using appropriate valve box and secure cover
• Technique to remain functional, without need for major restoration works, for a period of ten years
• Installation to be environmentally sensitive and responsible e.g. not waste water, any soil waste used responsibly
• Technique can be readily and safely installed and cost effective
• Water delivery program to be able to be accommodated within existing irrigation scheduling capability
• Technique to be repairable should tree root and soil conditions interfere with the functioning of the system.

The City of Melbourne decided, in early 2007, to investigate watering techniques that could be used to maintain trees, located in high profile streets and boulevards, in a healthy condition. The trial investigated a range of drip watering and tree watering well products. Restricted root systems, highly variable soils, high traffic and high exposure characterize these trees.

The trial was carried out in Royal Parade, Parkville, where elm trees are positioned in both medians and nature strip areas. The medians are typically raised concrete structures, approximately 500 mm high and 4 metres wide.

A range of water well products and a watering trench were trialled with the watering trench found to perform best.

The key evaluation criteria included the (a) distribution of water (vertical and lateral), (b) presence of overflow and (c) installation requirements.

The trench was considered to potentially have the advantage of providing a wider distribution of water, allow a relatively large volume of water to be delivered rapidly and, if necessary, allow grass to be grown over the surface.

The basic dimensions of the trench was approximately 1.2 metres long, 300 mm wide and 300 mm deep. The total volume of the trench cavity is approximately 110 litres. Both sand and graded gravel (7 mm), referred to as quarter minus, was used as the trench medium.

The trench version which performed best consisted of quarter minus gravel. The quarter minus provided ample void water space for water storage (approximately 30%) was stable when saturated. The washed sand material was found to become soggy or slushy and provided virtually no top loading support. This is an important consideration for a watering system in these areas is that that present no undue risk to the public.

Water distribution from the trench was found to be variable however typically in the range of 500 mm laterally, beyond the edge of the trench, at a depth of 500 mm.

The water jet technique was considered to be the most effective in terms of constructing this type of trench. However the watering jet technique is potentially expensive and requires considerable support in terms of roadway traffic management restrictions to accommodate the truck.  The trench watering system has been installed in the majority of Royal Parade, sections of St Kilda Road and in sections of Birrarung Marr

The change to sub-surface delivery of water has improved the health of trees. Generally trees have taken one summer season to adapt to the new source of water and by the following summer are displaying greater health with fuller canopies and minimal indications of drought stress.

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Norfolk Island Pine showing tall, tiered effect.

Origin

Norfolk Island

Description:

Specific epithet refers to the distinction between the juvenile and adult leaves.  Juvenile leaves narrow, incurved, generally softer, while adult leaves are rigid, overlapping and lanceolate.  Grey-black bark, flaking, deep pink beneath.  Branches are held in horizontal whorls of 4-7.  Ovoid to globose female cones found in small numbers held upright in the uppermost branches.   Growth rate is reported as being fast, however will be dependent on nursery production method, landscape site conditions and after-care maintenance.

Tolerances:

A large tree that can adapt to a range of soil conditions (as long as well drained) and is drought tolerant once established.  Moderate tolerance to waterlogged soils.  High tolerance of winds also salt laden winds in coastal situations. Not seriously affected by pest or disease.

Root space:

Based on mature size, tree would require approximately 176m2 area or 106m3 root volume. (Crown projection method based on 15m diameter canopy due to narrow form of species).

Availability:

Common.

Uses & management:

The most widely cultivated of the araucarias. Norfolk Island Pine is well suited to coastal situations where, in Australia, it has become an iconic species.  Possibly used in coastal towns as landmarks for shipping.  Species is suited to urban landscapes, both coastal and inland.  Also used as street tree where space allows (Zone of upheaval 4.0m to 5.0m diameter) .  Good tree for open space. Norfolk Island Pine can also be used as an indoor plant and is often seen as a Christmas tree.
Prune to central trunk otherwise little pruning is required.  Supplemental irrigation to establish trees is essential.
Roots are surface orientated and can lift hard surfaces.  Consideration will need to be given to allowing room for both upper crown development and root buttress expansion.

Featured Tree© Tree Logic Pty Ltd 2008
Ref:
Rowell, R. J. (1996) Ornamental conifers for Australian gardens. UNSW Press.
Spencer, R. (1995) Horticultural flora of South-Eastern Australia. Ferns, conifers & their allies. UNSW Press.

Click to download printable pdf

The tree is listed on the Victorian Heritage Register as being of state botanical significance as the only known example of this specie or hybrid in Victoria. With the help of Rob Bodenstaff (Arbor Centre, WA), BS Callow, Gyra Engineering and various local sub-contractors including P & D Cranes, Maffra Trenching and RTL Transport; Tree Logic set about process for transplanting the 40 tonne tree.

How we did it

A root ball of over 5 meters in diameter was carefully excavated, roots were trimmed and the ball framed. A steel raft frame was constructed under the tree so that it may be lifted with a crane and placed on a transport vehicle. The base lift method of transplant was chosen over the more common practice of pin lifting, to reduce damage to the tree and to take a much larger root ball. Once lifted on to transport the tree was driven across the Princess Highway into Victory Park. The tree was planted proud of existing site grade to avoid any potential water logging of the root ball, was mulched and the site cleaned up.

The job was completed within 5 days. LaTrobe City Council will look after the tree for the next 2 - 5 years until it becomes re-established in the landscape. Parks and Gardens staff lead by Mick Cantwell were trained by Tree Logic in the nuances of managing and maintaining the tree over this critical period and we will be dropping in from time to time to see how the tree fares. Early indications are that it’s a happy team at Hawthorn.

Lee Carr Tree Logic’s Office Manager and Wayne Bloxidge Team Leader Outdoor Services from Tree Logic recently attended the 9th National Street Tree Symposium in September joining others passionate about sustainability practices in their industry.
A big thank you to everyone who supported the Tree Logic Stand at the Symposium.

With increased crowding within urban sprawl, the need for greater emphasis on wise use of water and reduced water use.
Street verges becoming the future water catchment areas by directing water runoff into nature strips rather than into the stormwater systems. Use this water for street tree production/improvements before it becomes wasted/lost to our bays and oceans.
Greater emphasis on species selection. Field demonstrations showed an interesting look at root development of elms and native gums that may improve the tree selection process. Fine matted roots to the canopy edge on elms and large far reaching roots on gum trees.
Much broader and improved look at risk assessment of mature trees and trees in general in urban settings. Greater management of targets and tree crown management rather than a narrow focus on tree removals. Especially when considering cavity and hollow defects.

The long-awaited release of the newly registered Bayer SilvaShield® Injectable Tree Insecticide has arrived.

Current practice has many applicators using non-registered products such as Confidor® to undertake trunk injections.  Confidor was formulated as a soil drench and while some control may be achieved, there are chemicals in Confidor that actually inhibit uptake through the tree’s vascular system and reduce the effectiveness of any control.

Better Results
Bayer’s SilvaShield is a specifically formulated trunk injectable that has been in testing for some time. If you are an owner of trees that are likely to receive trunk injection as a control option this season, you should specify that SilvaShield is to be used to maximize your tree management spending.

Tree Logic offer a range of trunk injection equipment to allow applicators to make the best use of SilvaShield with the Arborjet (US) product range now available in our online store.

Refillable Injectors Coming Soon
Tree Logic has also been working on developing a small low-cost refillable trunk injector that will be perfect for the application of SilvaShield.  These small refillable injectors are in the testing stage now and are likely to be available in the next few weeks, Stay Tuned!!

VicUrban appointed a team of consultants lead by a joint venture between Black Kosloff Knott and Taylor Cullity Lethlean (BKK/TCL) to develop concept designs for Harbour Esplanade.
Tree Logic is working as a sub-consultant to BKK/TCL providing arboricultural information to the areas of tree selection, tree planting systems complimentary to Water Sensitive Urban Design (WSUD), tree stock assessment and procurement, and tree maintenance scheduling.
The project area comprises 700 metres of public space between Docklands Drive to the north and Bourke Street (adjacent to Docklands Park) to the south.

The Millennium Seed Bank Project (MSBP) is the largest ex situ conservation project ever conceived. The Royal Botanic Gardens, Kew and its partners will have banked seed from 10% of the world’s wild plant
species by the end of the decade. These will not be just any plants, but will include the rarest, most threatened and most useful species known to man.

The Millennium Seed Bank Project seeks to develop a global seed conservation network, capable of safeguarding wild plant species. This will make direct contributions to national and global conservation/development programs, and will make a big contribution to meeting the objectives of the
Convention on Biological Diversity (CBD). The current project will run until 2010.

Acacia pubescens

This new product will be the only bulk liquid trunk injectable insecticide available for use in Australia and will mean that applicators will be able to access a registered product to offer their clients for a range of tree injection uses.

In the past the trunk injection industry has seen many applicators using non-registered products such as Confidor® to undertake trunk injections. Confidor was formulated as a soil drench and while some control may be achieved, there are chemicals in Confidor that actually inhibit uptake through the tree’s vascular system and reduce the effectiveness of any control.

This will change with Bayer’s SilvaShield as it is a specifically formulated trunk injectable that has been in testing for some time.

If you are a owner of trees that are likely to receive trunk injection as a control option this season, you should specify that SilvaShield is to be used to maximise your tree management spending.

Tree Logic offer a range of trunk injection equipment to allow applicators to make the best use of SilvaShield with the Arborjet (US) product range now available in our online store.

Tree Logic has also been working on developing a small refillable trunk injector that will be perfect for the application of SilvaShield. These small refillable injectors are in the testing stage now and are likely to be available in the next few months, Stay Tuned!!

Name: Centurion
Height: 100 –101 metres.  Because the sight to the very top of the tree was partially obscured by the tree’s healthy crown, it may be taller. According to Forestry Tasmania staff the head of Centurion had previously broken off and it was likely the tree was once higher.
Trunk Diameter: 405 cm

Name: Triarius
Height: 86.5 metres, Clear sight to the very top of the tree.
Trunk Diameter: 390 cm

Centurion becomes the tallest known tree existing in Australia, the tallest Eucalyptus tree in the world, the tallest hardwood tree in the world, and the tallest flowering plant in the world.  The previous tallest known existing hardwood tree was “Icarus Dream”, a Mountain Ash (Eucalyptus regnans), measured at 97 metres in the Styx Valley (west of New Norfolk) in 2005.

Centurion and Triarius have survived the major bushfire events of 1934 and 1966/67, which burnt to the west and immediately east of the trees respectively.  The trees are now afforded protection through Forestry Tasmania’s Giant Trees Policy.  This policy provides for the protection and management of all Giant Trees on Tasmania’s State forests. To qualify as a Giant Tree, trees must be at least 85 metres tall or 280 cubic metres in volume.

Despite the Giant Tree policy, “El Grande” a Giant Mountain Ash discovered in 2002 was killed by Forestry Tasmania during burning in 2003 that was part of a woodland clearance exercise.  El Grande - which stood at 79 metres (260 feet) - was thought to be the largest tree in Australia in terms of volume and grew in the Florentine Valley about 100km northwest of Hobart.  El Grande collapsed last year.  Lets hope Centurion fairs better than El Grande and other Giant Trees threatened by forestry activity.

Information on Tasmania’s Giant Trees can be found at the Giant Tree Consultative committee website www.gianttrees.com.au. The committee was established by Forestry Tasmania to provide independent advice on the protection, management and promotion of Giant Trees.

Information about Victoria’s tallest trees can be found at The Department of Primary industries website www.nre.vic.gov.au/virtualexhibition/trees.