To bend the willow: the basket willows (Salix spp.) in New Zealand

Abstract

The young shoots (rods) of willow (Salix, Salicaceae) have been used for basketmaking for at least two thousand years. The species, hybrids and varieties used for basketmaking are known to vary in rod dimensions and flexibility. However, knowledge of such variation amongst basket willows to date remains largely experiential. As the numbers of practising basket-makers diminish worldwide, we are in danger of losing an understanding of the characteristics of a good basket willow, and the necessary cultivar diversity with it. The basket willows in New Zealand, intentional introductions from the mid-19th century onwards, provided an opportunity to investigate what constitutes a ‘good’ basket willow in a novel environmental and evolving social context; as a restricted assemblage of species and cultivars, and as a basket-making material. This thesis explores the role of basket-makers, entrepreneurs, nurserymen and government science in New Zealand over the past 150 years, in determining the palette of willow cultivars available to New Zealand basket-makers, and their experiences of cultivars grown under New Zealand conditions. This thesis also presents the first detailed analysis of the morphological and biophysical properties of a range of wild and cultivated first and second year Salix rods to determine if basket willow cultivars show a unique set of traits. Variation in the morphology, physical properties and flexural traits of 46 basket and shrub willow clones currently held in the New Zealand National Willow Archive and 72 wild genotypes grown under common conditions was measured. Basket and shrub willows varied considerably in mean numbers of shoots produced in their first season of growth, their length, angle of lean, degree of taper, width to length quotients, in branching patterns and shoot curvature. Variation tended to be continuous rather than discrete. Furthermore, cultivars in New Zealand did not always perform according to existing Northern Hemisphere information. However, species level differences could be detected when multiple characters were considered together. Salix viminalis and related hybrids were morphologically distinct from most other basket willows, a pattern that was also evident in their physical properties and flexural traits. The flexural traits of known basket-making cultivars, non basket-making cultivars, and wild genotypes, determined in three-point bend tests, were not consistent across species overall. The combinations of physical properties and flexural traits associated with use for basketry were species, and often cultivar specific, although toughness may be a key trait irrespective of variation in other physical and flexural traits. A good basket-willow is the outcome of a complex of morphological, mechanical, cultural, social, historical and environmental interactions. Preservation of Salix cultivar diversity is important to ensure cultivars are matched to local growing conditions and because basketmakers depend upon variation amongst cultivars in order to continue producing a large and varied range of basket-ware. We have a responsibility to ensure that domesticated willow continues to be a source of basketmaking material in the future.