KidsGardening.com: Ideas for using gardening as a tool for learning
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This website is focused primarily on school gardens, but there's little here that couldn't be done as easily by homeschoolers. The "Classroom projects" section includes a wide variety of gardening related projects-- from poetry and photography to meteorology to cooking and food preservation and more. "Thematic explorations" has information to help you plan your learning garden, including ideas for families without much space to devote to the project. If you want even more, check out the "pollinator curriculum", a free complete curriculum for upper elementary, which seems ideal for homeschooling, IMO. "Exploring Hydroponics" is another intriguing curriculum described on the site-- it includes how to begin hydroponics with available materials, like 2 liter soda bottles.
