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

Abstract

Summary. 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 Pultenaea parviflora grown in mixes of peat : perlite : sand 4:7:3, coir : perlite : sand 4:7:3 or coir:perlite:sand 3:7:3. No differences in rooting or shoot regrowth were detected even though there were some differences in the chemical 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 capacity) of the mixes did not change substantially over time. In the second experiment, Brachyscome multifida var. dilatata, Correa ‘Dusky Bells’, Eucalyptus melliodora and Grevillea × gaudichaudii were potted into peat : sand 1:2, coir:sand 1:2 or coir:sand 1:3; whilst Callicoma serratifolia and Lomandra longifolia were potted into peat:sand 1:2, coir:sand 1:2 or coir:sand 1:5. All 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 3743-1996) with the exception of pH which was initially slightly higher than recommended in all mixes. Analysis of growth characteristics over 14 months did not reveal any clear overall differences between mixes, indicating that coir was comparable with peat.