Pupils at city schools in England will plant mini-forests in their playgrounds under a government-backed scheme.
Schools are being offered free packs of saplings by the Woodland Trust, partly funded by the Department for Environment, Food and Rural Affairs.
Overall, the trust and Defra hope that one million trees will be planted by 2020 with a focus on urban schools.
The aim is to "bring an oasis of green" into school communities, said Woodland Trust chief executive Beccy Speight.
A pilot group of nearly 800 schools to enrol received their packs of one and two-year-old saplings last week, to plant by the end of the month, amounting to 35,000 trees.
By 2020 government money will have paid for 400,000 trees, with the rest funded separately by corporate sponsors and other partners.
Pupils at Griffin Primary School in Wandsworth, south London, will plant their trees on Monday, with help from environment secretary Elizabeth Truss who will be there to mark the start of the full scheme.
Head teacher Chris Beazeley said in this urban area, many pupils would not have had the opportunity to visit parks or woods "or get up close to nature".
"By planting trees at school we can give them that experience and teach lessons in an engaging way," he said.
"Many of our early years children prefer to learn outdoors. It is good for them physically, socially, and developmentally and the trees will make our school a greener and more pleasant place."
Ms Speight said she hoped the experience would kick-start lifelong relationships with the natural world.
"The scheme offers schools that have found it hard in the past a new way to plant trees," said Ms Speight.
Under the scheme, the trust will help city schools with small playgrounds find local open spaces to plant their trees.
Ms Truss said: "Children across the country will be able to grow, learn about and identify native trees including birch, hawthorn and hazel, giving the chance to understand and connect with nature and make their school grounds and neighbourhoods cleaner and greener."