First, here's a portion of one of our beet beds, sown August 25th. That's not quite three weeks ago, and these greens are already in need of thinning (and weeding). Baby greens can be a bit labor-intensive to harvest, but they are the way to go if you want a crop that could be ready to eat in under a month.
Here's today's harvest from that August 17th sowing, from only about as much space as is shown in the first photo. They're piled high in a colander 11" across and 5" deep!
This crop isn't just good for salad, though they're tender enough to be eaten raw. We like to cook them in a frittata, or to make them the star of a greens gratin or vegetable tart. The flavor is like a cross between beets and spinach, and at this stage, is pretty mild. Good stuff!