(Amaranthus retroflexus) I use this in my multi grain cereal almost every day. It is a very small grain (.04″)and is very high in lysine  which helps the other grains which are mostly low in lysine to make a complete protein.  It seems to sweeten the cereal up.  I use about 1 1/2 teaspoons to my half cup of whole grains. Again, Amaranth is high in protein and fiber. It is a prime source of lysine, calcium, magnesium, iron, vitamin E and polyunsaturated fatty acids. Amaranth is gluten-free.

It may be one of the “weeds” growing in your garden.