These mostly
unwanted plants are sometimes exotic invasives, and most multiply with
abandon, "like weeds". I control them by pulling them before
the plants set seed and by mulching in areas where I do not want them
to grow. Mulching does not always work, because some plants
are so persistant that they sprout in pinestraw.
Some, such as False Foxglove, Golden Aster, and Gibasis, are left where
they grow because they are ornamental. Many look like classic "weeds"
until they bloom, as do certain expensive plants found in
nurseries. Some are real nightmares, such as Mulberry Weed.
A special thanks to tyrlych of Gardenweb.com for identifying six of the
plants above.