Growth of selected Australian plants in soilless media using coir as a substitute for peat

In 2 experiments coir fibre (coconut mesocarp) was compared with peat as a propagation or potting mix component for selected Australian native plants. The first experiment investigated root and shoot growth on cuttings of Pul tenaea parviflora grown in mixes of peat:perlite:sand 4:7:3, coir:perlite:s and 4:7:3 or coir:perlite:sand 3:7:3. No differences in rooting or shoot re growth were detected even though there were some differences in the chemica l and physical characteristics of the mixes. Over 2 months, pH of the coir mixes rose from 3.3 and 3.9 to 5.8 and 5.6, respectively, whilst electrical conductivity decreased from 0.253 and 0.127 dS/m to 0.095 and 0.103 dS/m. The physical characteristics (air-filled porosity and water-holding capacit y) of the mixes did not change substantially over time. In the second exper iment, Brachyscome multifida var. dilatata, Correa 'Dusky Bells', Eucalyptu s melliodora and Grevillea x gaudichaudii were potted into peat:sand 1:2, c oir:sand 1:2 or coir:sand 1:3; whilst Callicoma serratifolia and Lomandra l ongifolia were potted into peat:sand 1:2, coir:sand 1:2 or coir:sand 1:5. A ll taxa and potting mix combinations were subjected to a 'less frequent' or 'more frequent' watering regime. The physical and chemical characteristics of the mixes were all within the Australian standard recommendations (AS 3 743-1996) with the exception of pH which was initially slightly higher than recommended in all mixes. Analysis of growth characteristics over 14 month s did not reveal any clear overall differences between mixes, indicating th at coir was comparable with peat.