It is not easy to forget annual forget-me-not, Myosotis sylvatica. Even if it dies back early in the heat of summer, it will probably throw plenty of seed to regenerate through next winter, and bloom again by next spring. It can easily naturalize in damp or riparian areas, and might be considered to be a weed; but like nasturtium and foxglove, it is a polite weed that is not aggressively invasive.
The tiny blue flowers start to bloom while winter is still cool, and then get a bit more abundant as the weather warms in the beginning of spring. Some modern garden varieties bloom with pink or white flowers. Tender leaves are about 2 or 3 inches long, and less than an inch wide. Soft stems creep laterally, but do not get far. Mature plants are less than a foot tall, and 2 feet wide.
Between autumn and early spring, seed can be sown directly where plants are desired. Because they are so tender, plants are not often available in nurseries. Forget-me-not is a nice understory plant to larger rhododendrons and up-pruned shrubbery, or covering for daffodils, freesias and other spring bulbs. They want regular watering and rich soil and can be happy in cool partial shade.