Ludwigia hexapetala (Hook. & Arn.) Zardini, H. Gu & P.H. Raven, Syst. Bot. 16(2): 243-244 243 1991. (Syn: Jussiaea hexapetala Hook. & Arn.); 




Ludwigia hexapetala (Hook. & Arn.) Zardini et al.
Common name: Water Primrose
Sorry …, I could not show you evening primrose as promise.
But thank you for the query as it helped me to find a plant I had not seen it earlier.
When photographing the plant from a ditch in a garden here I thought it to be a species of Oenothera, but while processing my photographs especially to upload for … I was struck by persistent calyx on the top of fruit, some thing not found in this genus. I finally identified it as Ludwigia hexapetala.
Of the four species of the genus in California, this one is characterised by erect habit, alternate narrowly ellipitic leaves, yellow flowers about 2.5 cm across, with 5-6 petals and sepals.

Serendipity will contrive to bring you to evening primrose and then me to your pictures or vice- versa…
no hurry, it will happen suddenly
when you least expect it