As part of the Alonso-Stepanova lab at NCSU, there is a website that includes experiments for elementary school kids:
For many centuries, people have been fascinated with plants and wanted to learn more about them. People have been growing plants (mainly for food) for many thousands of years. Not only do plants give us food and plain look nice, but they also provide building materials (wood, for example), clothes (cotton T-shirts), furniture (wooden tables), toys (blocks) and a lot more.
To study plants, people not only grew them, but also did a lot of experiments, learning many interesting things about plants along the way. Experiments are a fun way to look for an answer to a question or to test an idea. Are experiments only for adults? Not at all! Kids like you have a lot of questions (don’t we all?) and you may be surprised to find out that you are more than able to answer many of the questions by yourself or together with friends and parents! The experiments described in this website/brochure can help you design and perform real experiments. They will help you learn about how plants grow. And the best thing about these experiments is that they are practically free.