Last year, I let an enormous lambsquarter plant grow in the back raised bed so it would go to seed. I picked quite a bit of seed from it, then it fell over of old age (I guess - or maybe it wasn't well rooted in the soft soil). This year, of course, the entire bed would be filled with baby lambsquarter plants.
I like lambsquarter, but that was a lot of it! We (my daughter and I) planted turnips and beets in the bed, then I "weeded" out the lambsquarter as it came up. Most of it was frozen for later use. I usually freeze greens, but this year I want to can them. I'm still picking... er, weeding them from the garden and letting some of them outside the bed grow. Those big leaves make excellent sandwich "lettuce."
Lambsquarter, called wild spinach by some, is more nutritious than spinach and can be used the same way, raw or cooked. It is "good source of Niacin, Folate, Iron, Magnesium and Phosphorus, and a very good source of Dietary Fiber, Protein, Vitamin A, Vitamin C, Thiamin, Riboflavin, Vitamin B6, Calcium, Potassium, Copper and Manganese" according to Nutrition Data.
It's kinda cool to harvest a crop that I didn't have to plant, don't have to water or baby along.