Supplementation of juniper on the Lizard Peninsula, Cornwall, UK

Summary

Juniperus communis subsp. hemisphaerica survives in Britain at only two known coastal sites, and in Cornwall it is reduced to just 13 individual plants on the Lizard Peninsula's Gew Graze Valley, first recorded there in 1871 but since eroded by fire and grazing. With the surviving plants skewed toward males and showing no evidence of natural seed regeneration, Eden Project horticulturists set out to secure the population rather than expand it outright. Each of the 13 wild plants was mapped by GPS, tagged, and logged in the project's plant database, then propagated by cuttings to build a genetically representative ex situ collection and to raise 195 young plants for a new, fenced planting nearby, since young junipers are vulnerable to grazing until established. Twice-yearly health checks track the wild plants, while fruit production and seed counts are recorded annually from both wild and cultivated stock and tested for germination, which is known to take up to two years and to suffer from poor seed viability in this population. The project reports propagation by cuttings has worked well and a seed sample is being banked with the UK National Tree Seed Project, but cuttings alone cannot restore lost genetic diversity, and no successful seed-grown regeneration has yet been achieved. The project rates itself a failure on that basis, despite maintaining and supplementing the existing population.