Forestry Fact Sheet Number 8

 

The Green Triangle Region, which includes the South West of Victoria and the South East of South Australia, is a region with good soils, high rainfall, cool summers and mild winters. These conditions make the area particularly suitable for growing Tasmanian blue gums in plantations.

 

Eucalyptus globulus, the Tasmanian Blue Gum, is the best hardwood species for growing in pulp­wood plantations in this region. It is fast-growing, high-yielding and ideal for pulpwood production in short rotations of 10-12 years. Well managed trees growing on good sites may reach a height of two metres in the first twelve months.

 

Growing eucalypts in plantations involves several steps:

1. establishment

2. management

3. harvesting and marketing of the timber

 

Establishment

Site Selection

This first step in the establishment process is very important because the future growth of the trees and the ultimate return depend on the choice of site. Productivity will vary with factors such as soil type, pH, rainfall, presence of underground water and site drainage. Naturally the best sites will grow the best trees, but a range of other less-than-ideal sites are, with careful management, quite capable of growing productive plantations.

Cultivation

Once the site has been selected, the next step is to prepare the ground for planting. Ideally this preparation should begin about 6-8 months before planting. Recommendations for cultivation will vary according to the specific site. The two types of cultivation most frequently used are ripping and mounding. Mounding is particularly important on wet sites.

Weed control

This is extremely important as it ensures that all soil moisture is available for the trees.

 

Poor weed control means poor tree growth!

 

Weeds which need particular attention include sorrel, bracken, phalaris and flatweeds. Controlling these may require spraying several times before planting.

 

A typical regime for cultivation and weed control is:

1.         Sorrel control in spring. Some additional control may be necessary closer to planting.

2.         Bracken control in summer.

3.         Ripping to shatter hardpans, loosen stony and clay soils or to prepare bracken areas.

4.         Weed control after the break of season, the first autumn rains, which is particularly important if weeds such as sorrel are present.

5.         Mounding is necessary on wet sites and is usually done six weeks after sorrel control (April-May).

6.         Residual weed control to stop further weed germination in strips approximately 1-2 metres wide along the planting lines. Alternatively, to eliminate any weeds still present a knockdown and residual herbicide mix can be applied in strips approximately 1-2 metres wide along the planting lines.

Planting

This takes place in June-July, approximately six weeks after residual weed control. Seedlings are planted in rip lines or on top of mounds using a Pottiputki planting tool. 3000 trees per day can be planted using this tool.

 

The recommended stocking rate is 1000-1250 trees per hectare, depending on the site; with the lower stocking rate used on poorer sites. Specific stocking rates should be discussed with PIRSA Forestry at the time of ordering seedlings. Seedlings can be ordered through PIRSA Forestry. Orders ideally should be placed by the end of January in the year of planting.

Management

Once the trees are planted they require little maintenance but should nevertheless be regularly monitored for the presence of pests, nutritional deficiencies and weeds for at least the first two years. Vertebrate pests such as rabbits, hares and birds can cause considerable damage. Cockatoos, ducks and magpies are often responsible for uprooting seedlings.

 

Management includes:

·      Second-year weed control, if necessary, in the autumn-winter following planting;

·      An application of fertiliser if the trees show signs of deficiencies;

·      Regular and frequent monitoring of insect and vertebrate pests;

·      Annual maintenance of firebreaks.

 

Once the trees are about three metres high, careful grazing by sheep for short periods of time can be used in the plantation to keep the grass down.

Costs

Typical costs for establishing and managing Tasmanian blue gum plantations are given below in Table 1. All costs are approximate. More detailed costs should be investigated for specific sites. For further indicative costs assistance is available from PIRSA Forestry.

 

Table 1: Typical costs for Blue Gum Plantations.

Item	Type	Cost ($/ha)
Weed Control	Bracken	69 (+ 15 application)
Sorrel	45 (+ 15 application)
Residual spraying	80-110
Ripping		150
Mounding/Cultivation	100
Seedlings (1136/ha @35c)	400
Planting	110-120
Insect control	55
2nd year weed control	110 (may not be necessary)