Understanding the variability of vegetable fibres: a case study of harakeke (Phormium tenax)

Fibre properties may be an important source of information to identify, conserve and protect intraspecific diversity within culturally significant fibre plants such as harakeke (Phormium tenax, New Zealand flax). Māori weavers recognise differences in whītau ^* (fibre aggregate prepared using traditional practices) extracted from leaves of different harakeke cultivars. However, tensile properties of fibre aggregates are reportedly highly variable. The aim of this study was to investigate variation in fibre aggregate physical and mechanical properties among leaves harvested from different fans within two bushes representing different cultivars of harakeke. Tenacity, extension to maximum load, specific modulus and specific energy to maximum load of fibre aggregates differed between the bushes, and also among leaves within each bush. Leaf width and thickness were weakly correlated with fibre aggregate properties suggesting that wider, thicker leaves yield tougher and more pliable fibre aggregates. Variability among leaves differed according to the property measured, and was highest for fibre aggregate length and lowest for specific energy to maximum load. Although fibre aggregate tenacity (or strength) is commonly used to compare intra and interspecific fibre properties, specific modulus, extension at maximum load and specific energy to maximum load were all more appropriate for identifying intraspecific differences in harakeke fibre properties.