To know a plant, grow a plant!
I had gone to a Wisconsin Society of Science Teacher conference a few years ago and got an interesting activity which I hadn't tried until this year. The main idea was to use two sizes of Brassica seeds and see which one germinates first. To make it more interesting, the seeds are glued to a wedge shaped piece of filter paper and put into a small plastic test tube with a cap that can be made into a "necklace" and hung around a student's neck.
Another thing put into the tube is a wedge of millimeter graph paper so the growth can be measured without opening the tube. A small amount of water is added to the tube in order to facilitate germination. Of course, the filter paper will wick up the water to keep the seeds moist.
I have my students make a hypothesis beforehand about which seed they think will sprout first. This year's students were mixed on which they thought would sprout first and grow fastest. Since it was a voluntary experiment, I didn't have enough results to speculate on which was the fastest of the two.
Many thanks to Hedi for providing the seeds!