This is a relatively new cut flower export, and the project shows that rice flower could become an increasingly important part of the Australian wildflower industry.

The project was undertaken by horticulturists Mr Peter Beal and Dr Lois Turnbull, and experimentalist, Mr Leif Forsberg, all from the Queensland Horticulture Institute, and Mr T Slater and Dr John Faragher, both scientists at the Victoria’s Institute for Horticultural Development. Their work is part of the RIRDC’s Wildflower and Native Plants Program which aims to improve the profitability, productivity and sustainability of the Australian wildflower and Proteaceae industry.

The work included accessing and evaluating a wide range of genetic material, growing it in varying locations, improving pest and disease control, and applying postharvest practices.

Defining the most suitable varieties of rice flower and promising related species, and appropriate production and marketing practices still needs further work.

The Study

Field Trials

Evaluation was by measuring plant survival, growth and yield, flowering time and flower quality.

In Queensland, over the two-year trial period, there was good survival, growth rate, and rice flower yields of up to 98 stems per plant. The success was associated with use of well drained soils, moderate rainfall, use of fine leaf local cultivars and freedom from phytophthora root rot.

Table 1. Cultivars or selections of rice flower (O. diosmifolius) and other Asteraceae
used in coordinated field trials.
 

Species	Cultivar/selections (acronym)	Colour	Other
O. diosmifolius	O 'Cook's Tall Pink' (CTP)	pink	early flowering
O. diosmifolius	O 'Redlands Sandra' (44.7)	white	early flowering
O. diosmifolius	QDPI line 54.4 (54.4)	white
O. diosmifolius	O 'Cook's Snow White' (CSW)	white	late flowering
O. obcordatus	Knowfield OOK1 (OOK1)	yellow	late flowering
Chrysocephalum semipapposum	Knoxfield CSK1 (CSK1)	yellow

There was poor survival, growth rate and yield in Victoria and New South Wales and this was associated with lower prevailing temperatures, the occurrence of pest and diseases and poor adaption of fine leaf cultivars used. Mid-leaf cultivars may be more suitable in some situations in southern locations.

Onset of flowering of rice flower in Queensland occurred from mid-September to mid-October, with flowering occurring four weeks later in Victoria (early October to mid-November).

New Collections

By using different varieties and growing areas, it is possible to significantly extend the production season from August to February.

This includes a 14-week production season in south east Queensland from August to mid November using the O. diosmifolius/O. diotophyllus hybrids and pink and white flowered fine leaf and mid leaf selections of O. diosmifolius.

An extra 10–14 weeks, from November to February, is possible using species with white, pink, cream, brown and yellow flowers complementary to O. diosmifolius. These included Cassinia compacta, C. aureonitens and Ozothamnus obcordatus (October/November flowering) and Cassinia laevis, Ozothamnus rosmarinifolius and Cassinia uncata (December to February flowering).

Of 13 species (29 selections) collected from Tasmania, Ozothamnus rosmarinifolius (with dense flowering heads and late summer flowering) and O. expansifolius (with short stems and showy display) had commercial potential.
Commercialisation of germplasm

While germplasm has been distributed widely over Australia – for commercial evaluation in tropical and temperate locations for cut flowers and garden and potted plant use – further collecting of useful germplasm from the wild is recommended. There is a major need to identify genotypes with useful adaptation and either tolerance or resistance for direct use in cultivation, for use as protective rootstocks or in breeding. In addition, growers need to accept a major role in systematic evaluation of germplasm involving field and market requirements.

Diseases and disorders

Tolerance to Phytophthora and to root-knot nematodes (Meloidogyne spp.) has been documented in rice flower although useful field resistance has yet to be confirmed.

Postharvest

The response of rice flower to a number of postharvest treatments was investigated to determine the effect on vase life following storage and transport. The postharvest life also was measured against the physical characters of the cut stem and the various cultivars to determine if any of these factors also were involved.

During harvest and handling, the stems should be treated with a degree of care to prevent bruising of the tissues which will cause a localised tissue blackening. The stems should be cooled where possible. The postharvest life of the stems can be extended if they are rehydrated with water containing 50 mg/L chlorine, 0.01% agral and 250 mg/L aluminium sulphate, or 2 g/L citric acid, to assist in the uptake of water.

STS can be used to control leaf blackening in the mid-leaf form. Stems should be dipped in an insecticide or fumigated to remove the problems of insects hatching on the flowers. The vase life of the cut flowers can be improved if they are cooled. Use of a commercial flower preservative after transport may also be beneficial.

Summary

The production season has been extended to at least 14 weeks from mid-July to late October. And a 12-16 week commercial production season for rice flower is possible now that germplasm development has proceeded.
Export production increased from estimates of 300,000 stems in 1993 to 649,000 stems for 1996 (Japanese Plant Quarantine Service figures).

Since 1994, growers and nurseries have been very active in developing new cultivars and production sites. A 1997 grower survey indicated an estimated 33 rice flower cultivars and 22 locations were utilised by commercial growers in the eastern states and South Australia in 1997 to produce a substantial proportion of Australia’s export crop.

The research has indicated that exploiting new cultivars and new locations from the Atherton Tableland in Queensland to Millicent in South Australia, and to Cannington in Western Australia, is possible.