Participants in "Give It Some Welly for Woodland" will hold sponsored welly-boot-themed events of their own devising.
The Trust aims to planting 20 million trees a year as part of its goal of doubling Britain’s native woodland cover.
Supporter of the initiative Dame Judi Dench said:
"I am fortunate to live somewhere that is rich in trees, but so many places are not and the need for more native trees has never been greater, both for people and wildlife.
"This fund-raising campaign needs us all to put our best foot forward, and I urge everyone to get their thinking caps on and work together to give it some real Welly."