Look at all those pretty flowers in the garden... but wait, shouldn't I be clipping them off to prolong the harvest time?? Not necessary. To the left white flower is coming out from my parsley. So why would I let my parsley go into bloom? Because I want it to bloom and give me seeds later on. That way I can plant more through the summer and next year as well and I won't have to buy them in the store.
One plant will give me enough seeds for all my needs. I have other plants that I use for cooking so it's not a big loss. The same goes for my arugula and salad plants. For now I can still pick them but probably come weekend I will take them all out and plant seeds for fresh set of crops. But for now they'll be blooming and I'll leave at least few of them to go ripe so I can gather seeds. It's not a good idea to use the same crops in one place so where I used to have salads I'll probably put something else. I already spread some salad seeds where I had spinach and radishes. That way I can rotate them better.
And I'm going to do the same with peas, beans, onions and squashes if they'll grow too many at one time.
That's one of the reason I wanted to use organic and heirloom varieties so I can gather up seeds and dry them for later use.