I see these pretty pink flowers all the time around campus. What caught my eye
in particular as I was walking home from class is how these flowers tend to grow in patches along the grass. My research informed me that these flowers are native to the central United States and Mexico and often form “extensive colonies”.
These flowers go by many names: pink evening primrose, showy evening primrose, Mexican evening primrose, pink ladies, and pink buttercups to name a few. The species name is Oenothera speciosa.
I also found out 
that these flowers tend to open up during the evening (hence the name ‘showy evening primrose’), which is probably why I noticed them on my way home at 5 PM and have never seen them open when I walk to campus earlier in the day.
Reference:
https://www.wildflower.org/plants/result.php?id_plant=oesp2
iNaturalist Observation: