Conservation of the threatened shrub Hebe cupressoides (Scrophulariaceae), eastern South Island, New Zealand

Hebe cupressoides is an endemic shrub of the rain-shadow eastern mountains of New Zealand's South Island where it is a component of shrubland communities on recent surfaces such as alluvial terraces and colluvial slumps. While Hebe cupressoides is grown in cultivation, the range of this species in the wild has declined dramatically this century and is now known to be extant at only 15 of the 33 sites from which it has been recorded. Remaining populations are in general small and comprise predominantly large individuals; seedlings were only seen at three sites. Only one of the 15 remaining populations has > 100 individuals present. Germination of fresh seed is high (89–95%), but is significantly lower for 2-month-old seed. Germination is also substantially higher for seed germinated under full light than under even light shade, and is very low for seed germinated under heavy shade. We hypothesise that although browsing may be a factor in the decline of Hebe cupressoides, the almost complete absence of regeneration today is primarily due to an inability of seeds to germinate and seedlings to establish under the heavy shade associated with the introduced grass sward that now dominates at all sites. Restoration of Hebe cupressoides populations in the wild will require control of this introduced grass sward.