Citrus glauca

Common Name: Desert or Wild Lime.

Family: Rutaceae

(glauca; bluish, referring to the foliage colour)

Distribution

Semi arid and arid areas of New South Wales, Queensland and South Australia

Conservation Status

Not considered to be at risk in the wild.

General Description

The Desert Lime is a medium shrub or small tree generally 3-7 metres in height. It is confined to inland areas, usually on heavy, clay soils. The foliage is greenish-grey, with oblong leaves up to 50mm long by 5 mm wide. The stems are spiny with irregularly spaced thorns. Flowers are 10 mm across, white or greenish in colour and appear in late winter and spring. The flowers are followed by greenish/yellow fruits which are globular in shape and about 15 mm diameter.

Fruits

The fruits are edible and have a strong citrus flavour which is widely sought by "bush tucker" enthusiasts.

Other Notes

Because of its habitat, Citrus glauca is of interest as a grafting rootstock to possibly extend the range of commercial citrus crops. There is also potential for breeding to develop new citrus varieties.

C. glauca is not widely cultivated as it is generally unsuited to the wetter climates of the major population centres. It can be cultivated successfully in inland areas. The plant has a suckering habit which may need to be controlled in cultivation. Propagation is possible from seed but cuttings may be slow to strike. Grafting or budding onto other citrus stocks has apparently been successful.

Acacias

Rural Industries Research & Development Corporation

(Cut flowers and foliage)

by Margaret Sedgley and Francha Horlock*

Introduction

Acacias are recognised overseas as the cut flower crop mimosa, following cultivation over many years in southern France, Italy, Portugal and Japan. Species suitable for the cut flower and foliage industries are those with attractive characteristics including gray or green simple or divided leaves and prolific flowering.
With over 800 species, the genus has wide adaptation to cool temperate, tropical and arid inland climates. Acacias are tolerant of most soil types and have a range of uses. In addition to cut flowers and foliage, they are used for pot plants, tanning, timber, pulpwood, fuelwood, shelter belts, soil amelioration, perfume, fodder and bush tucker.
The main constraint to industry development is lack of cohesion in the cut-flower industry, and reluctance to communicate and co-operate. A further constraint is the lack of superior cultivars in Australia, which results in lack of uniformity in yield and quality of product. Export of fresh cut flowers and foliage is the area with most potential for expansion.
The most important personal skill requirement for the acacia flower and foliage industry, is recognition of the intensive nature of production. Plant care is essential for quality production and hence for success.

Key messages

o Natives exported to Asia, Europe and USA
o Japanese market is undersupplied
o Wide climate and soil tolerance
o Peak industry bodies are AF&PGA and FECA
o Supply northern hemisphere off season

Key statistics

o Natives exported to Asia, Europe and USA
o Japanese market is undersupplied E Wide climate and soil tolerance
o Supply northern hemisphere off season

Markets and marketing issues

Asia is the focus of export interest for the developing Australian acacia cut stem trade. The product is familiar to Japanese buyers through import from France, and from local production. Prices for flowering stems are high from September until Christmas, whereas buds and foliage attract lower prices. Pale lemon coloured inflorescences sell best from July to November, with a preference for darker golden flowers from November until Christmas. Europe currently supplies the Japanese market from December to May, providing a window of opportunity for Australian producers between September and December. The heavy odour common in many acacia species is not popular in Japan, where the demand is for more subtle fragrances. High quality and a vase life of a week are essential. Reduction in European exports to the Japanese market from 55,000 stems in 1991 to 23,500 in 1992 are due to poor quality product, and provide an opportunity for Australian producers. The price for Dutch product is ¥100 to ¥150 per stem (during August 1997, $A1 = ca ¥85).
Mimosa stems produced in France and Italy are marketed throughout Europe, Britain and the USA. The maximum demand period is during the northern hemisphere winter, from the beginning of November to the end of March. Individual growers or regional co-operatives sell either locally, or via central flower markets, from where the product is transported to Holland, Germany, Belgium, USA, UK, Sweden and Switzerland. Export accounts for 70% of the French crop, which had an annual turnover of 40-50 million francs (A$1 million) in 1993. Each market has its own specific requirements, and the industry provides product accordingly. The English and American markets require long stems of up to 70 cm with many small branches, the German market demands short branches between 25 and 40 cm for funeral wreaths, whereas the Swiss and Belgian markets accept a mixture.

Production requirements

Most current production is in coastal Australia and is based on relatively few species. Amongst the 800 plus Australian species, there is adaptation to all climatic zones, and production is potentially possible throughout the country (see map).
Many acacias are frost resistant, and within the genus there is tolerance of a wide range of soil types, including pH variation and high salinity. In general, acacias are easy to cultivate, but the cut flower species grown in France and Italy are both frost sensitive and intolerant of heavy soils. Overseas experience indicates that if a species is not adapted to a particular soil type then it can be grafted onto a suitable rootstock. For example, tolerance of the calcareous soils of southern France and Italy is achieved by using Acacia retinodes as a rootstock.
Young plants should be watered regularly, and for cut flower production mature plants must be watered to stimulate flush growth following pruning. During summer weekly irrigation is advisable for both young and mature plants.

Varieties

In Australia the species most commonly grown for cut flower and foliage are

Acacia baileyana, A. baileyana purpurea and A. dealbata, although many others have potential for cultivation.
These include

There are no superior cultivars of acacia available in Australia.
In the French industry, the A. dealbata cultivar Mirandole is the most popular, comprising 53% of the market, with the A. dealbata cultivar Gaulois at 26% and A. retinodes cultivars at 10%. The French cultivars are grafted onto seedling rootstocks.

Agronomy

Most acacia tubestock currently available in Australia is seed propagated, although methodology exists for vegetative propagation via rooted cuttings. Overseas, acacias for cut stem production are superior cultivars grafted onto seedling rootstocks. Acacias will tolerate most soil types, but very heavy soils should be mixed with sand and organic matter to avoid waterlogging. Before planting the ground is cleared, and the soil ripped to a depth of 40-60 cm. Young trees are planted in rows or along the contour lines of sloping sites, at a spacing of 1-6 m between and within rows. Planting is done in late autumn, or early spring in frost-prone areas, and cover crops are often grown.
Some work has been done to investigate glasshouse production of flowering Acacia stems, to avoid problems such as frost and bushfire. Sand, peat and gravel is used as the soil medium, with liquid fertiliser. A further advantage is that the plants flower three weeks earlier than outside, but there are also disadvantages, mainly in the increased incidence of disease problems.
In France, fertiliser is incorporated into the ripped soil before planting, at a rate of 500-1000 kg superphosphate, 150-200 kg potassium sulphate, 150-200 kg ammonium sulphate, 1000-2000 kg vegetable waste and 40-60 t manure/ha. After planting, ammonium sulphate is applied throughout the year after each pruning, and the fertiliser regime for mature plants is 0.6 kg superphosphate, 0.2 kg potassium sulphate and 0.4 kg ammonium sulphate per tree. Iron chelate is used to combat chlorosis in alkaline soils.
Regular pruning has long been used in southern France and Italy, both to control plant size and to induce flowering for specific cut-flower markets. Pruning of old wood is particularly important, as the flowering stems produced on old wood are inferior to those on new wood. Advancement or delay of flowering is achieved in the French mimosa industry by pruning, which serves to promote maximum flowering through the production of many lateral shoots. Pruning of the winter-flowering species A. dealbata involves thinning out and heading back at or shortly after harvest. For the summer flowering A. retinodes, more frequent and severe pruning is required to delay flowering until winter. This involves repeated heading back of two-year-old shoots to four or five buds to stimulate many fine shoots which will bear the flower buds. The first commercial cut-flower harvest is taken from three-year-old trees, with peak production at six years. Yield per tree varies from 10 kg for A. retinodes to 20 kg for A. dealbata.

Pest and disease control

Wood borers are the most serious pests of acacias in Australia. Larvae of beetles belonging either to the family Cerambycidae, the longicorn group, or to the family Curculionidae, the weevils, are most commonly responsible. Their presence is detected by frass at the base of the affected branch, or in serious cases by death. Borers are probably largely responsible for the short life of acacias in cultivation, and should be detected and treated early with injection of alcohol or dimethoate into the hole.
Another potentially serious pest of acacias in Australia is the leaf-eating beetle Paropsis, which can defoliate plants within a short space of time. The beetles are controlled with maldison and lead arsenate, but the problem is to know when an attack will occur. Larvae of leaf miners can also cause problems, including those belonging to the family Gracillariidae, such as Acrocerops plebeia which is a particular pest of A. podalyriifolia in Sydney. These make unsightly tunnels in the leaves which detract from the appearance of the stem and may cause defoliation. Leaf miners can be controlled using systemics such as dimethoate. Other pests of acacias in Australia include scale insects belonging to the superfamily Coccoidea, sap-sucking leaf hoppers, gall-making insects, and the Acacia bug, Eucerocoris tumidiceps, which causes unsightly black spots on the leaves where it has sucked sap.
In southern France, the most common pests of acacia plantings are psyllids. These sap-sucking insects lay their eggs on the foliage, and the larvae attack the young shoots and leaves. The pest is controlled with parathion and endosulphan. The scale insects, Aspidiotus hederae and Icerya purchasi, are controlled using white oil or methidathion in cool weather, but in warm conditions the predatory beetle Novius cardinalis is effective in controlling Icerya. Caterpillars and nematodes have also been reported as minor pests of acacias in France.
In Australia the main disease problem is Phytophthora cinnamomi which causes root or collar rot and leads to death of the plant. In southern France the main problem is Septoria rust, which causes a red colouration followed by leaf shed. Copper is used to control the problem. Rotary or manual hoeing is the most common method used to control weeds in the French industry.

Harvest, handling and post-harvest treatments

In France and Italy harvesting of cut flower stems, which are put into clean water or preservative solution, is done by hand using saws or secateurs. Some stems are marketed at the green bud stage, but in order to maximise returns most are harvested at the yellow bud stage. Stems are harvested just before flower opening, and the cut stems are forced into full bloom before marketing. They are placed in forcing rooms set at a temperature of 22-30°C and 85-95% relative humidity for 48-72 hours with no light. After forcing, the stems with open flowers are transferred to a drying room at a temperature below 12°C, after which they are graded according to stem length and packed. Bunches of varying sizes are wrapped, and are packed into cartons with details of the producer, the cultivar and the number and weight of bunches.
Flower opening during forcing and post-forcing vase life are improved by a post-harvest storage solution containing up to 10% sucrose, 200 ppm citric acid, 200 ppm hydroxyquinoline sulphate (HQS), 50 ppm silver nitrate and 50 ppm aluminium sulphate. Using this solution a vase life of 7 days can be achieved. Alternatively, commercial bud opening preservatives can be used.
In Australia recent research has shown that stems with yellow buds can be forced in a pulse of 1% sucrose, 0.01% detergent such as Agral, and 200 ppm aluminium sulphate for 16 hours at 10-20°C. Open flowers are treated in the same way, but can be pulsed at temperatures of 4-20°C. For transport, flowers should be pre-cooled and disinfested, then packed tightly in a carton. Packing stems in perforated sleeves and inserting stems in floral foam, soaked in flower preservative or chlorine solution, may improve quality. A vase solution of 1% sucrose and 50 ppm chlorine or a commercial preservative increases vase life.

Economics of production and processing

Economic analyses for new crops should be treated with caution, especially as so many acacia growers produce other crops as well. The following production figures relate to foliage for the domestic market.
For a farm in South Australia, producing more than 500,000 stems per year and receiving a price per stem of $0.25, the gross farm income in 1995 was $137, 213 for average yields and $151,073 for above average yields.
This represents a farm profit of $31, 261 for average yields and $45,121 for above average yields, with a return on capital of 6.6% and 9.5%, respectively. Annual per hectare expenses are estimated at $300 for plants, $150 weedicides, $750 pesticides, $100 power, $100 water, $160 fertiliser, $3000 labour, $1650 machinery hire, $250 fuel, $7500 harvesting costs and $3000 pruning. First grade blooms will return $0.25 per stem, second grade $0.10 and third grade $0.05. Overall annual expenses are of the order of $16,960 per ha, against income of $19,800, with a gross margin of $2840 per ha.
Potential returns from cut flower export to Japan are more lucrative. It is estimated that at a planting distance of 2 m ??3 m, production of 75,000 stems at year 4 would return
$45,000/ha. More intensive production at 1 m ? 1 m spacing is estimated to return 140,000 stems with an income of $86,400 per hectare at year 4. This is based on a price per stem of between ¥60 and ¥120 in the Japan Auction system or ¥100 to ¥120 for fixed pricing. The grower receives about half of this price after export costs are paid.

Key contacts

Margaret Sedgley
Department of Horticulture, Viticulture and Oenology
Waite Agricultural Research Institute
The University of Adelaide
Glen Osmond, SA 5064
Phone: (08) 8303 7242 or
(08) 8303 7248
Fax: (08) 8303 7116

Rod Jones
Melbourne Markets
Footscray, Vic.

Francha Horlock
Institute for Horticultural Development
Agriculture Victoria
Private Bag 15
South Eastern Mail Centre,
Vic. 3176
Phone: (03) 9210 9222
Fax: (03) 9800 3521

John Faragher
Institute for Horticultural Development
Agriculture Victoria
Private Bag 15
South Eastern Mail Centre,
Vic. 3176
Phone: (03) 9210 9222
Fax: (03) 9800 3521

Beverly Karpinski
AF&PGA (Australian Flora and Protea Growers Association)
Spring Valley
Frogmore, NSW 2586
Phone: (02) 6385 6222

FECA (Flower Export Council of Australia)
P.O. Box 137
Nedlands, WA 6009
Phone: (08) 9327 5563
Fax: (08) 9327 5683
Key references

Jones, R. and Horlock, F. 1994-95. Acacia Newsletters 1, 2, 3 and 4. Agriculture Victoria/RIRDC.
Karingal Consultants 1994. The Australian wildflower and native plants cutflowers and foliage industry: a review. RIRDC.
Primary Industries South Australia/South Australian Research and Development Institute 1995. South Australian Ornamentals Industry Development Plan 1995-2000.
Sedgley, M. 1996. Acacia. In: Horticulture of Australian Native Plants and Their Uses. Eds. K. Johnson and M. Burchett, New South Wales University Press. Chapter 8, 92-101.
Timmermans, U. 1989. Mimosa production recovers quicker than expected. Vakblad voor de Bloemisterij 18, 39-41.

*About the authors

Margaret Sedgley is Professor of Horticultural Science at the University of Adelaide, Department of Horticulture, Viticulture and Oenology. She has worked on improvement of native plants for ornamental horticulture for over 15 years. For address see Key contacts.
Francha Horlock is with the Institute for Horticultural Development of Agriculture Victoria, and works on production and postharvest handling of Acacia for cut flower and foliage.

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