Lesser Celandine (Ficaria verna -- formerly ranunculus ficaria)

 (AKA fig buttercup ...and pilewort by some)

 

  "There is a Flower, the lesser Celandine,
    That shrinks, like many more, from cold and rain;
    And, the first moment that the sun may shine,
    Bright as the sun himself, 'tis out again!"
 

 ~The Small Celandine." William Wordsworth

This invasive perennial in the buttercup (ranunculus) family is native to Europe and Western Asia. 

It is considered noxious in some US states because it can be fatal to some livestock. It is toxic to humans if eaten raw, and can cause contact dermatitis in sensitive skin, but has medicinal and nutritional properties nonetheless. 

The young leaves have been used to treat hemorrhoids. 

The protoanemonin found in fresh leaves is an irritant and mildly toxic but is suggested to have antibacterial properties if used externally. 

Heating or drying neutralizes the toxin and it is then used for its antispasmodic and analgesic properties.

The roots were traditionally boiled, fried or roasted as a source of carbohydrates. 

https://pmc.ncbi.nlm.nih.gov/articles/PMC9227133/

https://pmc.ncbi.nlm.nih.gov/articles/PMC3365867/