At least I think this is water primrose or Ludwigia octovalvis. Today the shrubs are about 6 feet tall. They started blooming in April and just refused to stop.
Water primrose is considered an invasive weed in some places. I can see how that might happen. Each seed pod had an unthinkable number of seeds. But the water primrose is a good nectar plant and native to Southern Texas so I feel comfortable in trying to grow one here. I’ve seen it listed as a zone 9 and above plant but I see it recovering each spring at the Mueller pond in Austin (zone 8).
When to sow: I planted the seed in late summer
Special treatment: none
Fresh or dried seed: fresh
Planting depth: Needs light to germinate
Preferred temperature for germination: unknown
Days to germination: 30
Vegetative propagation: Division
Daytime temperatures were hot ranging from 75-90. I used ordinary potting soil. Provide winter protection if the temperature dips below 20F.