Mechanical High Pruning

Note Number: AG1014
Updated: July 2007
Rhodey Bowman, Tatura

This Information Note provides technical information about pruning eucalypt plantation trees at elevated heights

Why Prune?

Figure 1. Local orchard pruners have easily adapted to pruning timber plantations.

Pruning is a simple way to add value to a plantation. It plays a major role in the production of quality timber since it allows growth of wood that is free of knots. Knots are the round shaped areas seen in sawn timber that are created when branches remain on the tree stem. They cause structural and visual defects, that can lower the value of the timber. A correctly pruned tree can potentially be worth 15%-50% more than the value of an un-pruned tree.

Most pruning up to the 2.5 m level, depending on one's height and equipment, can be conducted from the ground. Further lift pruning, up to 6.5 metres in height, requires some form of elevation. This has in the past meant ladders, pole pruners, long-handled pruners and pruning saws. These can have extra dangers, are very tiresome and labor intensive.

Within the Shepparton Irrigation Region in North Central Victoria, farm forestry growers have taken advantage of the local expertise of orchard pruners (Figure 1). Farm forestry has provided new employment opportunities for pruners during the off-peak season, which is around October/November. Unlike orchard pruning, timber trees can be pruned in Winter, Spring and Summer. Plantation pruning is similar to that of orchard pruning, with the key differences being which branches are cut and some of the equipment used.

Before you Prune

In most plantations the number of trees planted is much greater than the number of trees that are actually harvested. ‘Thinning' is used to reduce the number of trees competing against each other. Following thinning, trees have access to more nutrients, which enables better growth. Pruning is usually carried out prior to thinning. This means that those trees to be grown on to maturity need to be selected and marked for pruning. It has been recommended to prune at least 10% more than required for your final crop. This should be done to cover possible losses from storms, pests and diseases.

Equipment

Figure 2. Elevated platform or cherry picker, utilised for high pruning.

A common piece of equipment used by orchard/plantation pruners is a mobile elevated work platform (sometimes known as a ‘cherry picker', ‘travel tower' or even a ‘squirrel'). This type of machinery can be compressor or engine driven. The platforms are typically controlled with foot pedals, leaving the hands free to prune (Figure 2). Pruning equipment includes pneumatic or hydraulic pruners (Figure 3), secateurs, pole loppers and chainsaws. An air compressor powers the pneumatic secateurs and the hydraulic secateurs are powered by an engine and fluid hydraulics. These are usually mounted on the elevated platform or on a trailer. These implements allow the easy removal of branches up to 50 mm in diameter, depending on the equipment carried. There are also hydraulic or pneumatic chainsaw attachments available for any larger branches

Issues with Use

Equipment Considerations:

Figure 3. Hydraulic secateurs can make pruning quicker and therefore much cheaper.

• Ensure all equipment is in good working order; hydraulic hoses with no cuts/abrasions or dragging lines, wheel hubs secure, all guards in place, general equipment OH & S safety checks. 
• Victorian Workcover limitations exist on slopes greater than 5 degrees (1 in 11 gradient), on most units. Larger units can be manufacturer-modified for working on slopes up to 20 degrees. 
• Safe working distance between pruners should be 20 m. 
• In irrigation areas be wary of ground level hazards; channels, drains and irrigation checkbanks. 
• Foot Pedal controls need to have rubber covers to prevent slipping and accidental activation at height 
• Plantation branches are harder on blades than orchard trees. As with all pruning equipment, its important to keep it sharp and clean, with about ½ an hour a day required for maintenance. 
• The row width between trees needs to be about 3 m for the adequate manoeuvring of most common platforms. 
• Some air compressor models may need time to re-pressurise after cutting numerous large branches. 
• Consider the maximum prune height required and that which your equipment will allow. For example using an average Goulburn Valley platform and long handled pole pruners 12 m would be the maximum height; common platforms used in the Goulburn Valley (3-4 m), operator's shoulder height (1.5 m), extended long handled pole pruners (6-6.5 m).

Method:

• Ensure all branch stubs are removed and branch collars are not damaged, for the health of the tree and to allow growth over the knot.
• Smaller branches are difficult to see, especially on E. globulus with its ribbon like bark. (Note: E. globulus took the longest to prune in time trials).
• Prunings must be kept clear of controls to avoid accidental activation of platform.
• Pruning of larger & heavier branches may be risky at heights, even after double cutting. (Double cutting – is a cut underneath first, then from the top, to produce a cleaner cut). To eliminate risk of damage to the tree and the operator, reduce the weight of the limb by pruning further out on the limb prior to cutting closer and cleaner to the branch sleeve.
• It may be convenient to place the prunings into every second row to allow continued on-foot accessibility and the flow of irrigation. The platforms have no problems travelling over the prunings, but walking access may be limited or at the least made difficult for a short period of time until the prunings break down (1-2 seasons).
• If possible, stand pruning should be completed in one go as this will ensure the uniformity of the size of the knotty core within the logs. Uniformity will result in better marketing ease and a higher value end product.

Operator safety, health and well-being:

• All pruning equipment can be dangerous, Watch those fingers!
• Ensure all equipment and site checks have been conducted.
• Safety first – hard hat, high visibility vest, steel capped boots and in particularly eye protection is necessary to guard from branches. All protective gear to be kept in top condition. Gloves can be a hindrance and an added danger with secateurs.
• Do not wear excessively loose clothing.
• It is highly recommended to not work alone.
• Avoid work in rainy or windy conditions.
• Operator may get wet in mornings with heavy dews.
• Recently irrigated ground should be avoided, as it can be boggy and dangerous.
• Be aware of channels, drains and other ground level dangers as well as overhead power lines.

Advantages and Comparisons

Pruning using an elevated platform is usually quicker and therefore cheaper – between 0.5 and 1.0 hectare can be pruned per day. The work rate will depend on species, growth habit, stocking rate, future retention rate and the pruner's experience. Only prune the required final crop of trees, plus another 10% or so. There is no use in pruning trees that will be removed in later thinnings.

Ladder pruning at heights over 2 m requires certain safety standards, including secure footing and a climbing harness. Ladders suit steep sites and small jobs (Figure 4), with platforms being better on the flatter and larger sites. Ladders are also beneficial to owners that prefer the independence of doing the job themselves at their own pace.

Production Rates and Costs

A trial was undertaken in the Goulburn Valley in 2000, utilising two contract pruners, with their own elevated platforms. The aim of these trials was to determine the average time to mechanically high prune selected Eucalyptus species in a plantation environment from 2.5 to 6.5 m above ground. Single row at a time pruning was compared to double row at a time pruning, with no difference found between the methods. The travelling time between trees was found to be insignificant, compared to the time taken to prune (Note: one of the pruners had extensive orchard pruning experience but no plantation experience, the other pruner also had extensive orchard experience, but with reasonable plantation experience).

Figure 4. Pruning utilising a pruning ladder and safety harnes (Courtesy of the Australian Master Tree Grower program)

The results (Table 1) show that a contract pruner should be able to prune around 15 trees per hour for E. globulus, and 20 trees per hour for E. grandis, E.saligna and E. camaldulensis. Table 1. Average times taken to high prune Eucalyptus species with mechanical platform

At this trial, the local pruners, with no travel and accommodation expenses, were paid $25.00 per hour, therefore 8 hours was at a cost of $200.00, with the contractors supplying all their own equipment.

Experienced Farm Forestry plantation managers are also available. They can assist in formulating the job specifications and have pruning sub-contractors working under their specialist guidance to ensure adherence to the growers interests. The 2002 costs for these types of services, which include the pruner payment, equipment, travel and accommodation, were around $36 - $ 40 per hour.

An experienced Farm Forestry contractor of the north east of Victoria, indicated that the cost of bringing mechanical pruners and operators across from the Goulburn Valley, was well justified due to the increased productivity (Figure 5).

Contractual Issues

When employing a contractor, a formal written contract should to be entered into. It should include a detailed description of the job specifications and responsibilities of parties involved, including all legislative components. The contract detail will alter with the size and complexity of the job however at a minimum the contract should include all responsibilities, expectations, schedules and payment details.

Formal checks are also necessary to ensure that the contractor has adequate and up to date insurance cover for all plant and/or equipment, worker/s compensation and public liability. Ask to see certificates! There also needs to be inclusion and adherence to OH & S regulations and the ‘Code of Practice for Timber Production 2007'.

Training 

Figure 5. Pruning in an elevated position has many advantages, for both the pruner and grower.

Training and accreditation with elevated work platforms, is only required if the platform's arm extends more than 11 metres. Training for elevated platforms is available from some TAFE (Technical and Further Education) providers.

The Australian Master Tree Grower Program (MTG) offers training in Farm Forestry, including pruning. The MTGis a partner with The University of Melbourne Department of Forestry, local coordinating groups, agencies & landholders. Farm Forestry extension officers in Victoria may also offer pruning training.

Organisations and Contacts

DPI Private Forestry website

• Australian Master Tree Grower Program (external link)

References & Further reading

• Allen, R. (1999) Clearwood (Stem) Pruning, DPI, Unpublished.
• Bowman, R. (1999) Farm Forestry Flyer: Shepparton Irrigation Region Farm Forestry Network, Orchard Pruners in Plantation. Unpublished.
• Walker, G. (2000) Safe Operating Procedure Plant and Equipment, Orange Jolosapede, DPI Tatura, Unpublished.
• Washusen, R. & Reid, R. (1996) Agroforestry and Farm Forestry: Productive Trees for Shelter and Land Protection in the North- East Victoria, The Benalla Landcare Private Forestry Group.

Personal Communications

Arnold. D., 2002, David Arnold Planning and Contracting, Personal Communications.

Acknowledgements

Suzanne Johnstone was the original author of this document and the previous version was published in July 2002.