After reading up on radicchio I did some reading on broccoli in order to discover when I should harvest, this being my first time to grow it.  This site was the most helpful.  It said: 

When you see a flower head beginning to form in the center of the plant, check its growth every day. Ideally, you harvest broccoli while the tiny buds are tightly closed. If the buds begin to swell or show yellow (the flower petals), cut the head from the stem right away, no matter how small it is, because the opening buds have a mealy texture. After cutting the main head, leave the plant to grow bite-sized side shoots in the axils of the leaves. 

Well, I hadn't checked it yet today, and yesterday it looked great, so I thought I'd go check, and sure enough, it had little yellow flowers forming!  So I cut it.  Yesterday might have been the prime time to harvest it, and I'll know that for the future.  Already one little side shoot is growing.  

I also remembered to take pictures of the little yellow squashes and first tomatoes that have already begun growing.

I also harvested some more kale, but didn't cut the plant off yet.  And I picked three scallions which were good sized.