The idea is that individual trees on a street will have a dollar value. If someone damages a particular tree, the culprit could be liable for a fine reflecting that value.

The Barr government is taking advice from the authorities in Melbourne where a similar scheme operates. One tree there is valued at $54,000, according to ACT minister Chris Steel.

The dollar value of the tree would be calculated with a formula which would take into account its thickness and where it is. In Melbourne, a tree's value depends on its "amenity" and its "ecological value" as well as its "trunk diameter at breast height" and other factors.

The ACT scheme will need legislation but the minister envisages that "before the end of the year".

The government plans a bigger "urban tree canopy" to give shade to 30 per cent of the streets in the city over the next 25 years. That will mean planting 450,000 trees.

Some Canberrans love trees outside their homes but the minister conceded some did not. "We do see some tree-damaging activity in the community," he said.

Neglect is the other problem. The ACT government waters the trees it plants on streets for five years. After that, it is the responsibility of the local residents, particularly the house-holder next to the tree.

Mr Steel said a tree shading a house could cut temperatures in summer by as much as 10 per cent, so cutting electricity bills as well. He wants Canberrans to tell the government where they want trees to be planted.

He was joined at the tree planting in Watson by two government employees who tour the city identifying good places to plant.

Dijitha Mani was a software engineer in India before coming to Canberra a year ago. Her colleague, MD Saddam Hossain was an accountant in Bangladesh.

Neither has a full visa giving them the right to work in what are highly-skilled and well-paid jobs in Australia. In the meantime, they audit Canberra's tree population, seeing which trees are healthy and which need tender love and care. They also look for new sites for planting, noting power cables and sewage pipes.

"This is a really good job," Mr Hossain said.

"We are working for the community. It makes me feel very proud."

"It's small, small steps and we reach high," Ms Mani said, referring to her ambitions.

As tree auditors, they work as a two-person team going through two suburbs a week. They start before dawn to avoid the rush-hour.

"It is fun. It is enjoyable," they said together.

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