Juniper planting guidance December 2021
This outline guidance is drawn from the most current understanding of juniper propagation and the pathogen Phytophthora austrocedri. Compiled by Sarah Green, Forest Research.
1. Is the destined planting site an existing juniper population with the potential for natural regeneration? If so, don’t plant and instead improve management for natural regeneration. This is by far the best way of ensuring long term resilience in the population. If planting is deemed to be the only option i.e. where small, moribund populations occur or in new woodland creation schemes:
2. Any planted juniper should be raised from genetically diverse local material in a nursery operating stringent biosecurity standards (LINK) and which does not import plants. Inspect the nursery to ensure these standards are being met. Plant out 100% visibly healthy juniper plants that are in bare-root form to avoid transfer of Phytophthora pathogens that can exist, unseen, in pot soil/compost.
3. Avoid planting any nursery-raised juniper within 500m of an existing juniper population due to risk of spread of P. austrocedri which is greatest up to 500m from an infected plant. Increase this distance to more than 1km if there is the potential for vector transmission of plant debris/soil between the sites (i.e.via deer, sheep or human recreational activity).
4. When on-site ensure that high standards of biosecurity are met – using water plus a recommended disinfectant (i.e. Propellor) to clean boots, tools and other equipment of all soil and plant debris before and after entering the site.
5. If juniper are showing symptoms of foliage browning, this could be due to P. austrocedri infection in the root system and lower stem. Therefore it is important to test the root/stem/branch phloem for Phytophthora rather than the foliage, which is desiccated and not itself harbouring the pathogen.