Oxalis stricta L., Sp. Pl. 435 1753. (Syn: Acetosella chinensis (Haw. ex G.Don) Kuntze; Ceratoxalis stricta (L.) Lunell; Oxalis corniculata var. dillenii (Jacq.) Trel.; Oxalis corniculata var. stricta (L.) C.C. Huang & L.R. Xu; Oxalis cymosa Small; Oxalis dillenii Jacq.; Oxalis navieri Jord.; Oxalis repens var. stricta Hatus.; Oxalis shinanoensis T. Itô; Xanthoxalis cymosa (Small) Small; Xanthoxalis dillenii (Jacq.) Holub; Xanthoxalis stricta (L.) Small; (=) Oxalis europaea Jord.);
Oxalis stricta, called the common yellow woodsorrel (or simply yellow woodsorrel), common yellow oxalis, upright yellow-sorrel, lemon clover, or more ambiguously and informally “sourgrass”  or “pickle plant“, is an herbaceous plant  native to North America, parts of Eurasia, and has a rare introduction in Britain.
It tends to grow in woodlands, meadows, and in disturbed areas as both a perennial and annual. Erect when young, this plant later becomes decumbent as it lies down, and branches regularly. It is not to be confused with similar plants which are also often referred to as “yellow woodsorrel”.
Commonly considered a weed of gardens, fields, and lawns, it grows in full sun or shade. The alternate leaves of this plant are divided into three heart-shaped leaflets (a typical trait of other species of Oxalis) that can grow up to 2 cm wide. These leaves curl up at night (exhibiting nyctinasty), and open in the day to perform photosynthesis. The mature seed capsules open explosively when disturbed (a very similar trait to that of the mature seed capsules or fruits of plants found in the genus Impatiens) and can disperse seeds up to 4 meters (about 13 feet) away. The flowers of the plant are hermaphroditic, blooming from July to October.
All parts of the plant are edible, with a distinct tangy flavor (as is common in all plants in the genus Oxalis).
The leaves and flowers of the plant are sometimes added to salads for decoration and flavoring. These can also be chewed raw (along with other parts of the plant, but not the root) as a thirst quencher. The green pods are pleasant raw, having a juicy crisp texture and a tartness similar to rhubarb in flavor.
The leaves can be used to make a flavored drink that is similar in taste to lemonade, and the whole plant can be brewed as a tisane that has an aroma somewhat like that of cooked green beans.
The juices of the plant have been extracted from its greens as a substitute to common vinegar.
(From Wikipedia on 30.6.13)
The leaves contain oxalic acid, which gives them their sharp flavour. Perfectly all right in small quantities, the leaves should not be eaten in large amounts since oxalic acid can bind up the body’s supply of calcium leading to nutritional deficiency. The quantity of oxalic acid will be reduced if the leaves are cooked. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.
(From PFAF )
Oxalis stricta L. : Attachments (4). 2 posts by 2 authors.
There was a lot of discussion on Oxalis corniculata L. & O. stricta L. in the Balsaminaceae, Geraniaceae and Oxalidaceae Week in March, 2013 (https://groups.google.com/forum/#!topic/indiantreepix/P4fmSszJaYg). … showed the distinct features of these mentioned species and also gave some useful links and a very good paper of Nesom (2009). Recently I have captured few photographs of Oxalis stricta L. which blooms in summer from Lisle, Illinois. This looks very similar to O. corniculata L.. But the erect nature of stems (not stolon like), sparsely pilose margin of the leaves and solitary or arrangements of flowers in regular cymes are the key features for its identification. Fruits are not available in that time. Please find the attached pictures of Oxalis stricta L.
Fruits of Oxalis stricta L. : Attachments (4). 1 post by 1 author.
Here is the flowers and fruits of Oxalis stricta L. (Oxalidaceae)
Place: Lake shore drive, Chicago
Date: 20th June, 2013
Oxalis stricta in FOI : 5 posts by 3 authors.
Thingnam ji’s Images of Oxalis stricta in FOI shall be of Oxalis corniculata and not of Oxalis stricta (USA) as per images and details herein.
You are right. No other feature visible to compare too.
Here is Oxalis stricta that I photographed from Fremont California in September 2016.