Great idea, but bring it a step further: Don't buy cut Christmas trees this winter - buy one with roots, and plant it after you take down the decorations. Ours almost did not survive a harsh winter, but is now growing about 3 feet per year. Seeing it growing tall gives us great memories of a past Christmas and lets us know it is grabbing CO2 out of the atmosphere with every inch it grows. And, it's beautiful! We'll definitely do it again and again.

The best practice is to grow the plant really from seeds or a little sprout. You should rather avoid buying already grown ornamental plants, especially those shipped from tropical regions. The exploitation of wild plants in the tropical regions is a severe issue. An example is the endangered cycads (see http://www.cites.org/eng/com/pc/14/E-PC14-09-02-02-A1.pdf Page 14).

great idea! its so simple anyone can do it! it also helps more than most people realise

I have two mint plants and a ficus tree on my windowsill in my dorm room on the 7th floor. It's like my own little greenhouse, and I use the fresh mint in my sun tea ^^* Just proving that you can plant just about anywhere.