Excerpt:  Gardens are more than just pretty flowers and tasty vegetables and fruits.  More than 82 million households or 71 percent of the U.S. population gardened in 2007.  These people know that spending a little time in the yard tending a vegetable or flower garden, planting a tree or shrub, or mowing a lawn not only makes for a more beautiful and healthier world, but creates a more relaxing, peaceful, and connected life in our families, neighborhoods, and country.

Excerpt
From Creating Theme Gardens with Children.

A garden - the perfect classroom. In a medium that is hands-on and does not have to be censored, a garden can nurture the innate curiosity and creativity in your child or the adult child in you. It can keep you and your child learning and curious and possibly sow the seeds of a lifelong hobby, interest, or even career.

Of course, science is the obvious "course" in the garden, with botany, biology, horticulture, and ecology lessons already prepared. Math, art literature, and even social studies activities can also be integrated into your gardening "curriculum."