Here are a few statistics on the benefits of landscaping:

Landscaping can add as much as 14% to the resale value of a building and speed its sale by as much as 6 weeks.
Source: “Economic Benefits of Landscape”, Associated Landscape Contractors of America.

By spending 5% of the value of your home on the installation of a quality low maintenance landscape, you could boost the resale value by 15%, earning back 150% or more of your landscape investment.
Source: Taylor, C. 2003. “Fertile Ground”. Smart Money, March 2003.

Properly selected and placed plants can lower home heating and cooling costs by as much as 20%.
Source: “Economic Benefits of Landscape”, Associated Landscape Contractors of America.

A tree shading an outdoor air conditioner unit can increase its efficiency by as much as ten percent.
Source: U.S. Department of Energy, 1995

You can burn as many calories in 45 minutes of gardening as in 30 minutes of aerobics. One hour of weeding burns 300 calories (the same as walking or bicycling at a moderate pace), and manual push mowing of the lawn burns 500 calories per hour (the same rate as playing tennis).
Source: Taylor, M.K. 1990. “The Healthy Gardener”. Flower & Garden March/April:46-47.

Trees, shrubs, turf, and groundcovers trap and filter dust and other pollutants out of rainwater. Plants benefit from the nutrients in this particulate matter and prevent it from becoming a source of water pollution.
Source: Washington State Nursery and Landscape Association

Plants improve air quality. ‘One tree can remove 26 pounds of carbon dioxide from the atmosphere annually, equaling 11,000 miles of car emissions. Landscape plants, including shrubs and turf, remove smoke, dust, and other pollutants from the air. One study showed that 1 acre of trees has the ability to remove 13 tons of particles and gases annually.’
Source: “Enhancing Our Environment Through Landscaping”, Virginia Cooperative Extension, 1996.