Brown boronia is endemic to the south west of Western Australia, where it is commonly found as an understorey species. However, most of the commercial boronia farms in Australia are based on the north and east coasts of Tasmania.
The most suitable growing regions for brown boronia have been identified as the coastal regions of the South West of Western Australia, the north, north east and east coasts of Tasmania, and southern coastal regions of Victoria.
Boronia has reasonably specific soil requirements, preferring a soil pH(water) between 4.0 and 5.0, however trials have shown the plant will grow in soil with a pH of as low as 3.5 and as high as 6.5. The soil should have high organic and low clay content, with high flower production being obtained on well-drained acid sands. The natural vegetation on this preferred soil type is usually a coastal heath or bracken fern.
Soil should be tested for phytophthora and nematodes and also for residual phosphorus as boronia, like many Australian natives, does not tolerate high levels of phosphorus. Boronia does not like warm moist soils and losses from root rots may occur in these conditions.
The cool temperate regions of Western Australia, Victoria and Tasmania are well suited to boronia production, particularly the coastal regions of these areas. Brown boronia is reasonably hardy and can survive temperature extremes, from the dryness of a Mediterranean-type climate to the frost and snow of Tasmania.
币游注册The rainfall in these suitable growing areas is generally sufficient for production, however irrigation is recommended for young seedlings and for maximum flower yield.
Temperature and photoperiod requirements for boronia are quite specific. The plant will remain vegetative at temperatures higher than 25°C and any flowers that have initiated will most likely abort. A cool period is required for boronia to initiate flowering. In autumn, the ideal weather conditions for maximum flower number are approximate night temperatures of 10°C, day temperatures of 15°C, a 10-hour day length and full to 50% sunlight. These requirements may restrict the climatic range in which boronia can be commercially produced.
Commercial varieties for oil/extract production from Boronia megastigma 币游注册have been selected for improved yield, agronomic performance and disease resistance, however these are only available through a licence agreement with the owners of the lines.
Planting and crop management
币游注册Strong winds can damage boronia plants so windy sites should be avoided or windbreaks considered. Land preparation may be as little as minimum tillage and planting as the site presents itself; alternatively, the site may be cleared and levelled to remove large tree roots, which may be a source of soil-borne diseases.
As boronia seed is difficult to germinate, boronia plantations are established using transplants derived from the vegetative propagation of clones from mother stock. Depending on the planting design, densities up to 19,500 plants per hectare are used in Tasmania and between 7,000 to 10,000 plants per hectare in Western Australia. Rows should be aligned north to south.
币游注册Slow release fertilisers should be applied to boronia; the fertiliser should be low in phosphorus, as boronia will not tolerate high levels of phosphorus. Irrigation is not necessary but recommended to achieve maximum yields and may aid the establishment of a crop.
Caution should be exercised if growers are considering re-planting a plantation with declining production as a re-plant disorder has been identified amongst existing growers. A comprehensive management plan has been devised to address this. Further information on planting and crop management can be found in the New Crop Industries Handbook.
Weeds, pests and diseases
币游注册A competitive plant population of boronia should reduce weeds in plantations and mulching can also provide good weed control. Particular weed problems may need to be managed, however herbicide use should be kept to a minimum to reduce any residual contamination of the boronia oil/extract.
币游注册Pests of boronia include psyllids, black scale and brown scale, Rutherglen bugs, stem borers, cutworms and nematodes. Integrated pest management systems should be practised to manage these pests, such as cultivation, use of insecticides and pruning.
Boronia is quite susceptible to root rot diseases such as phytophthora and armillaria. Phytophthora is a significant issue for boronia production in Western Australia. Good sanitation practices should be adopted to avoid these diseases, such as the introduction of disease-free plant stock and the sterilisation of machinery and other equipment.
币游注册Boronia rust can be a significant problem in plantations but there are registered pesticides to manage the disease. Checking to ascertain that there will not be any problems with residues before spraying is important, particularly if contaminants then reside in the oil/extract.
币游注册Growers should consult with an advisor or the industry association about management programs for weeds, pests and diseases. In some cases it may be necessary to obtain a minor use permit from the (APVMA) to use pesticides not registered for boronia or the growing region.
币游注册Any browsing or grazing animals, such as rabbits, bandicoots, sheep and cattle should be fenced out of a boronia plantation as they will graze on and disturb the plants.
For detailed information on pest and disease management for boronia production see for Western Australia and more generally the New Crop Industries Handbook.