They will now act as training contacts within their own organisations, and could form part of a wider network being developed in response to the current outbreak of Chalara dieback of ash trees.
The representatives from the botanic and heritage gardens and public parks sectors completed training on plant and tree diseases and best practice in plant health and biosecurity.
FERA plant health head public engagement Dr David Slawson said:
"Our trees in particular are facing an unprecedented threat from pests and diseases, and it is vital that everybody, Government agencies and key non-Government organisations, work together to combat the threat. Government cannot do this alone, and it is vital that we develop expertise in other organisations to help.
He added: "A priority now is to investigate whether these new trainees can form part of this wider network and act as the nation's early warning system for new threats."
Workshops were held at the National Trust's Erddig garden near Wrexham, RHS gardens at Wisley and Harlow Carr and The Royal Botanic Garden, Edinburgh.
National Trust lead on Plant Health Ian Wright said: "Our gardens and woodlands have suffered attacks from a number of pests and diseases, and we have responded by making plant health a priority across the Trust. These workshops have created a new core group of knowledgeable staff who will embed best practice principles across the Trust's estate."
RHS chief scientist Dr John David added: "Sadly, new pests and diseases can enter our gardens on imported plants, and escape into the countryside. For this reason, the country's gardeners have a major role to play in combating the spread of plant pests and diseases."