Mr Johnson said trees were needed in deprived areas
Boris Johnson has said he would scrap the mayor's official newsletter, The Londoner, to fund a major tree planting scheme on streets throughout London.
The Conservative candidate pledged to plant 10,000 trees across 40 areas by the end of his first term, should he become mayor of London.
He said the "small gesture" would improve thousands of Londoners' lives.
Mayor Ken Livingstone and Green Party candidate Sian Berry say Mr Johnson "cannot be trusted" with green issues.
Mr Johnson will launch his environmental manifesto later this week - which will include the pledge to plant the trees by the end of his first term.
The scheme would see an average of 250 trees being planted in each of 40 areas "that need them most" - working with environmental charities.
Mr Johnson said he would pay for the £1m programme by scrapping The Londoner - the free newsletter sent to millions of homes and produced by the mayor.
Alan Craig Christian Peoples Alliance & The Christian Party
Chris Prior Stop The Congestion Charge party
One London party
Gerard Batten UKIP
Ken Livingstone Labour party
Left List party
English Democrats party
Richard Barnbrook BNP
Sian Berry Green party
Winston McKenzie Independent
John Flunder Senior Citizens' Party
Both Conservatives and Liberal Democrats have called for it to be withdrawn in the run-up to the 1 May election - complaining that the 20-page publication is "propaganda".
Mr Johnson, who highlighted his pledge at a tree-planting ceremony in Redbridge, said: "In the last few years a third of boroughs have seen a decline in the number of street trees - the mayor has done nothing to reverse this trend."
He said some of the most deprived areas had no trees on the streets at all and he wanted to distribute them "equally around the capital".
"Our current mayor is out of touch with everyday Londoners. Tree planting may appear to be a small gesture, but will actually improve the lives of thousands of Londoners."
Last week the Green Party candidate Ms Berry urged her backers to put Mr Livingstone as their second choice on their ballot paper.
If none of the candidates gets more than 50% of votes at the first count, all but the top two candidates are knocked out and their second preference votes shared out.
Ms Berry said she "could not bear" the idea of Mr Johnson becoming mayor and accused him of opposing the Kyoto Treaty and the £25-a-day charge on the least fuel efficient cars in London.
The Liberal Democrat candidate, Brian Paddick, said his party was committed to making London Europe's "greenest" capital.