Answering a question:

for Tim, who did not leave a link-

Arugula blossoms look like this:


They begin to produce long, green seed pods from the bottom of the stem up. These VERY gradually turn yellow or purple as they mature. Eventually, they dry and turn papery and brown:


They burst open when they dry. If you let them mature (which takes a surprisingly long time), you will have arugula coming up everywhere for years to come!