Yellow Wood Sorrel
Also Known as lemon clover, yellow wood sorrel is often found in many back yards. Easily identified by its' shamrock, 3 heart shaped, folded, leaves and the 5 petaled tiny flowers. Some refer to it as "sour grass" or "pickle plant" but most just call it a weed, as it grows in full sun or shade and in meadows and woodlands. Its' runners will spread nearly indefinitely. Oxalis Stricta is its' Latin name. Oxalis literally means "sour".
All but the roots are edible raw but the oxalic acid can prohibit the body from utilizing calcium so ingesting large quantities are not recommended.
Medicinally it is used for dry mouth, swelling and as a diuretic. Extracting (boiling) the leaves are good for quenching thirst and breaking a fever. Additionally decoctions are used for treating urinary disorders, as a blood cleanser, strengthening a weak stomach, increasing appetite and reducing vomiting.
This "weed" is very high in vitamin C. 20 pounds of foraged plant will yield 6 pounds of juice which can then be crystallized into 3 ounces of salts of lemon. This usage is said to be better than epsom salt.
We have a large patch of this growing nearby the house. Even after mowing the yard, it returns within a day or two. I often catch the little ones rolling and dancing around in it. Of course foraging as they go.
Note, we have a wild edibles class in which we identify and journal about our back yard discoveries. So our children are taught first and foremost the golden rule of "if you can't 100% identify it, then you don't eat it!". This learning and self made book is then used as a field guide when hiking and camping. It also serves as a survival course, as well as meeting many other academic categories such as handwriting, science, and even art.