Public: Forestry
Trees planted on buildings   (+3, -1)  [vote for, against]
Half building, half giant planter

This will minimize air pollution by placing soil on a rooftop of a building (preferably a skyscraper, since skyscraper rooftops are normally flat) and planting trees and bushes atop. Moss could also be added for extreme measures. This could work for large cities with lots of smog and pollution, or on top of factories to minimize the drastic effect of its smoke to the sensitive enviroment.
-- croissantz, Aug 20 2004

Google for "green roof" http://images.googl...afe=off&sa=N&tab=wi
[Worldgineer, Oct 04 2004]

Green Roof
[Worldgineer, Oct 04 2004]

Roof trees http://www.greenbui...uide/images/2.2.jpg
[Worldgineer, Oct 04 2004]

Trees Planted On Buildings http://www.teleobje...mbodia-gallery3.htm
Look how well it worked out at Ta Prohm, one of the settings for Indiana Jones and the Temple of Doom. [jurist, Oct 04 2004]

Hundertvasser haus
You can see a bit of the trees from this shot [energy guy, Oct 22 2004]

Heres another shot http://www.trophome...ndertwasserHaus.jpg
[energy guy, Oct 22 2004]

For [jsp] http://www.francisf...8&cid=10&partner=uk
(Second photograph) [angel, Nov 12 2004]

Manaccan church
"...built in the 12th century, is famous for the ancient fig tree growing out of its walls." [angel, Nov 12 2004]

Wookiee hut http://www.hrt.msu....ghouseGreenRoof.jpg
Looks like Wookiees already do this [AfroAssault, May 02 2005]

Kaiser Center Roof Garden http://www.liftech....s/roofgardendir.jpg
Includes low-growing trees, shrubs, grass, fountain [figmeant, May 27 2007]

Green roofs are not entirely rare these days. They generally use grasses and small plants because they have shorter roots, but trees are not unheard of. They are also useful for reducing rainwater load in cities, for reducing solar loads on roofs, and for insulation.

One interesting technique is to plant very leafy deciduous plants. In the summer they absorb most of the sunlight and keep the roof cool. In the winter the plants are bare, allowing the dark soil to absorb sunlight.
-- Worldgineer, Aug 20 2004

what [Worldgineer] said. also, large trees might make for dangerous projectiles if they came loose.
-- xclamp, Aug 20 2004

um, [x], any tree coming loose anywhere would probably be a dangerous projectile...
-- absterge, Aug 20 2004

um, [abs], yes true, but when they come loose on the ground they don't fall several hundred feet to the earth...
-- xclamp, Aug 20 2004

hmmm ... Angkor Wat and jungle-covered ruins throughout the Yucatan, Belize, and Guatemala spring to mind. Do you suppose this same idea was the starting point to the demise of those civilizations as well?
-- jurist, Aug 20 2004

We already have enough buildings with bricks or other things falling off them here in New York City. Yet the idea of Pine Trees atop many buildings letting loose pine cones that go whizzing down 50 or so stories and hitting people on the heads... the only ones to survive would be the tourists looking constantly up at the oh so tall buildings.
-- MrDaliLlama, Aug 21 2004

This has been done by an austrian guy named Hundertvasser. [see link]. [MFD]Baked.
-- energy guy, Oct 22 2004

There's a church in Cornwall that has a fig tree growing from the wall.
Just thought you'd like to know.
-- angel, Oct 22 2004

I'll get a shot next time I'm there, if I remember. In the meantime, see linky.
-- angel, Nov 12 2004

[angel] I'm sure both of your last two links vehemently prove your point, but the first link shunts me to a tertiary site when I select the second photograph, and the second link shows a fairly ordinary fig tree growing at an indiscernable level outside a 12th century church. You are rarely wrong, but I'm not getting the significance. (And, not to be rude, but is that the best environmentally-challenged roof tree England -- or even Cornwall -- has produced in 9 centuries? Surely not!)
-- jurist, Nov 12 2004

//I'm not getting the significance//
I'm not sure there is any. It's just a bit of vaguely related information.
Re the Francis Frith photo: hit the magnifying glass icon.
//You are rarely wrong//
-- angel, Nov 12 2004

It also looks to me that the first photograph is just a weird show house and someone glued a planter on the wall. The trees on top look like they're behind the house, not growing out of it.
-- croissantz, May 01 2005

The Sanger Institute just up the road from me is very proud of its green roofs (rooves?). They are covered with houseleeks, which are a kind of low- growing succulent. Not sure if it was done for environmental or aesthetic reasons, but houseleek-covered roofs apparently go back a very long way.

I'd worry about trees for structural reasons (how much soil would you need up there, and what damage would the roots do?), and (as noted) because of the hazard if they uproot or shed branches. Low-growing plants seem much simpler and meet the same aim (though not as dramatically).
-- Basepair, May 01 2005

Incidentally, the Teletubbies have this pretty well baked, at least with grass.
-- Basepair, May 01 2005

random, halfbakery