Commonly known as water hyssop (or waterhyssop if spaces aren't your thing), Bacopa plants aren't actually related to hyssops at all though the flowers bear a similarity. They can be annual (last one year) or perennial (coming back for 2 or more years), and most varieties prefer to grow in moist, amphibious conditions such as a pond's edge. If not submerged entirely - be sure to check your chosen variety's growing conditions before purchasing or planting.