I decided to try growing some of these. For the most part they are all easy to grow in cool weather. But they all go to seed and die when it gets hot. It turned out that my favorite of these is arugula. Arugula is quite spicy and many people don't care for it. I think it tastes sort of peppery-mustardy and I like it a lot. But, because it is pretty potent, it is usually mixed with other greens to give a nice balanced salad. It can also be sauteed in olive oil.
Every year I plant a patch of it. This year I planted it on one end of the raised bed where my basil resides. As usual, I harvested it week after week. As long as you don't pull up the whole plant, you can cut most of the leaves off of it and it will regrow leaves again and again until the weather gets hot and it goes to seed and dies.
One year I was too busy to pull up the old plants and just left them. Then a few weeks later I noticed tiny arugula plants coming up under the old growth that had died. I guess the dead plants shielded the ground from the sun enough that the seed could germinate and produce new arugula. So, I've been letting it go to seed like this ever since and then I have a new patch of arugula to harvest in the fall. Here is my fall patch this year.
Notice there are even a lot of plants that have regrown in the cement blocks that make up the edges of my raised beds. Today, I harvested enough to fill about 15 sandwich bags which we will sell at our farmers' market booth tomorrow.
Here is a close-up picture of what it looks like.