I find this project interesting and can see how the students would want to follow the outcome of the seed growth after launching with the balloons. I understand you used balloons to launch the seeds into the atmosphere. Not being a Science person I wondered how you launched the balloons to reach greater heights and then you were able to retrieve those seeds from the launch? Is there something attached to the balloons so that when they reach a certain height and remain at that level for a period of time, the balloon bursts returning the seeds by gravity? Unfortunately, when I was a student we never did neat experiments such as this.