Oenothera sp. - Evening Primrose. Not a weed in my book (at least the biennial one, O. biennis) as it attracts all sorts of cool moths and hummingbirds and also serves as a fine "trap crop" for Japanese Beetles, but it does reseed rather prolifically.

Oenothera biennis. Note the proper spelling, makes it easier to google. Just do not let it go to seed unless you want many more. Most of us consider them a weed but they are rather attractive.

Although it isn't a perennial.....

Not a favorite in my garden. I just yank them out when I don't like where they came up. Plenty left.

a marauding seed bearer that has certain world domination proclivities ..

my best guess... you will think.. oh its nice.. i will allow it.. and for a year or two you will beat it into submission..

and than one year.. life will get in the way.. and it will seed like the coming of the lord.. and you will spend to rest of your life cursing its very existence as you flame throw them all out of your yard.. not really daring if you burn good stuff ..

why dont you just cut that loop and get rid of it now... and live a happy good life ...

ken

ps: thats my wisdom for the day.. and for a shiny penny... i will tell you how i really feel about it ...

pps: and with this reseeding nightmare. the usual annual vs biennial vs perennial definition fails somewhat.. because after a year.. the plant will have each of the two years covered... so in effect.. acting.. or looking like a perennial ... there will ALWAYS be plants blooming to create a ton more seed ...