Officials in San Francisco want to help people celebrate a green Christmas.

The city's Department of the Environment and and and a group named Friends of the Urban Forest are offering alternative trees -- for $90 in a pot.

The idea behind the program is that, after the ornaments and lights are put away, the trees will be picked up for planting along city streets.

The trees are not exactly traditional, with varieties that include southern magnolia and New Zealand Christmas. But experts said those trees will do best in the Northern California climate.

Friends of the Urban Forest said more trees within the city help reduce water pollution by capturing street runoff from storms, help clear the air and add beauty and shade. It estimates that San Francisco streets have about 106,000 trees but can accommodate up to 120,000 more.