15 Green Projects for Under $500

Plant trees now on the south, east, and west sides of your house, and you can picnic under them in a couple of years. In five years, they may provide enough shade to let you run your air conditioner less frequently. And when the trees mature, they could save you as much as 40 percent on your cooling costs. Beyond shading your property, trees also help combat the "heat island" effect that occurs in urban areas, where concrete and asphalt absorb and hold in heat.

Two popular varieties are red oak for large lots (it grows to 70 feet) and trident maple for small ones. But before you buy any saplings, check with your city's public works department; some trees have invasive roots that plug water or sewer lines.

See How to Plant a Tree to watch This Old House landscaping contractor Roger Cook get a grower in the ground the right way. Check out How to Save Energy With Trees for more information on strategic planting.

Total: $35-$50 per tree