Exploring the growth dynamics of 𝘔𝘰𝘳𝘪𝘯𝘨𝘢 𝘰𝘭𝘦𝘪𝘧𝘦𝘳𝘢 Lam. and its invasive potential in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agriculture and Horticulture at Massey University, Palmerston North, New Zealand

Abstract

As global agricultural systems pursue climate resilience and multifunctional crops, 𝘔𝘰𝘳𝘪𝘯𝘨𝘢 𝘰𝘭𝘦𝘪𝘧𝘦𝘳𝘢 Lam. (moringa) has gained attention as a resource-efficient crop with potential for agricultural diversification, sustainable weed management, and high-value bioproduct development. This thesis assessed the feasibility and environmental implications of introducing moringa into New Zealand (NZ) farming systems through integrated climatic and ecological suitability, invasive risk assessments, and adaptation mechanisms through physiological and metabolomic analyses. Climate suitability and invasive risk assessments indicated that moringa establishment in NZ is limited to warm, frost-free regions, particularly Northland and selected North Island microclimates. Most of the country’s locations were classified as unsuitable due to low winter temperatures and frost frequency. Combined with poor cold tolerance and the lack of a persistent soil seed bank, moringa was classified as a low invasive-risk species under current and projected climates. Allelopathic studies showed that moringa root extracts exert species-specific and concentration-dependent effects. White clover (𝘛𝘳𝘪𝘧𝘰𝘭𝘪𝘶𝘮 𝘳𝘦𝘱𝘦𝘯𝘴 L.), a key pasture species in NZ was strongly inhibited, whereas perennial ryegrass (𝘓𝘰𝘭𝘪𝘶𝘮 𝘮𝘶𝘭𝘵𝘪𝘧𝘭𝘰𝘳𝘶𝘮 Lam.) and mānuka (𝘓𝘦𝘱𝘵𝘰𝘴𝘱𝘦𝘳𝘮𝘶𝘮 𝘴𝘤𝘰𝘱𝘢𝘳𝘪𝘶𝘮) were minimally unaffected. At higher concentrations, it significantly suppressed major weed species i.e., fathen (𝘊𝘩𝘦𝘯𝘰𝘱𝘰𝘥𝘪𝘶𝘮 𝘢𝘭𝘣𝘶𝘮 L.) and crabgrass (𝘋𝘪𝘨𝘪𝘵𝘢𝘳𝘪𝘢 𝘴𝘢𝘯𝘨𝘶𝘪𝘯𝘢𝘭𝘪𝘴 L. Scop.), supported by metabolomic evidence of bioactive phenylpropanoids, flavonoids, and benzenoids. Physiological and biochemical analyses confirmed that although moringa activates stress-defence mechanisms under cold conditions, these responses are insufficient to prevent severe declines in photosynthesis and membrane integrity at low temperatures. Overall, moringa cultivation in NZ is feasible only in frost-free zones or under protected systems, supporting a controlled, site-specific introduction framework. Through science-based regulation, regional targeting, and adaptive management, moringa could contribute to NZ’s transition towards more sustainable and diversified agricultural systems.