This can be used for many activities. This example is for preterite vs imperfect. Divide students into groups of 4 or 5.
Students use the target language to find what they have in common from their childhood and each member must agree they used to do the same activity when they were younger. THe group needs three sentences of what they have in common and it is writte on the plant holder. (We used to eat too much candy on Halloween. We used to ride our bikes. We used to obey our parents all of the time.)
Then each student write his or her name on a stem of the plant and in the individual leaf at the end of the stem write one thing that this student did one time that no other student has done. One time I went to Germany. One time I had ten stitches.
This activity will engage students in stating what they have done and asking othes if they have done the same.
For upper levels make it subjunctive Our parents want us to . . .
and then each student have something that is a unique demand from a parent.