Chaenostoma cordatum.

Brief description by NCSU Extension includes "does only fair in the ground; not as vigorous with heat; water generously."

Most of us know this as bacopa, a tender perennial typically grown as an annual. Often used in containers or baskets due to its trailing stems and cascading habit.

Great! Thanks all - and now I understand why it didn't last. There's something else growing there now. The planter bed it was in gets full sun for half the day.

Also, FWIW, there's a native bacopa here that looks very different, with tiny smooth leaves and flowers. It's a butterfly larval plant. Now that I know, I can see the similarities in the flowers.

there's a native bacopa here that looks very different

That's because the calling of Chaenostoma by the name bacopa is a similar occurrence to the referring to Pelargonium plants as geraniums. Except that in this case Bacopa is not in the same family as Chaenostoma.

Chaenostoma cordatum - Wikipedia

Bacopa - Wikipedia

Thanks for clarifying that, Embothrium 😃