"There's never been a more pressing time to plant trees," he stressed. "We can all individually make a difference and now is the time for us to get on with planting."
He added: "The National Trust cares for the great works of garden designers of the past and hopefully the Society of Garden Designers has members who are creating the great works of the future."
On the issue of plant sourcing, he said: "Wherever you can, buy local and think carefully about where you are buying from.
"Every specimen from abroad is a potential hub of diseases and these are villains of the plant. For the National Trust, hygiene is the name of the game."