When the weather gets nice, everyone loves flowers! Its even better if you can integrate them into an educational lab and reinforce science content.
This flower reproduction lab is one of my personal favorites. Students can dissect a flower and study the parts. I use the lab after teaching sexual reproduction, and students answer the questions "do flowers reproduce sexually or asexually?" through their lab work. In the lab, however, I have also included a more traditional version of the lab that allows students to learn about the parts of a flower. This lab also includes links to some great videos on flower parts, and suggestions on sources for flowers, and type of flower to use.
This was one of my students' favorites on course evaluations. I love the fact that they get to take a closer look at something they have probably seen, but never studied before. It would be a great lab for summer school, because flowers are so readily available.