A weed to one person may not be a weed to another, as many so-called weeds produce beautiful flowers, despite the relative worthlessness of the plant. In some cases, the attractive blossoms are the only asset for an invasive species such as loosestrife. In other cases, such as thistle, blooms eventually go to seed, providing valuable food for birds.
The list of flowering aquatic weeds includes the water lily, which produces a fragrant and beautiful white to pink flower. Loosestrife, a species that chokes waterways with its dense growth, has erect stalks covered with purple flowers; it closely resembles a living candelabrum. The water hyacinth is a notorious weed, growing in rivers and lakes of the warmer states in the United States. It is a terrible hindrance to recreational activities such as fishing and boating, and it clogs waterways, but it redeems itself slightly with a beautiful lavender flower splashed with colors such as yellow. Pickerelweed is another aquatic plant that can become a nuisance. It has a long spike that emerges over leaves shaped like a heart, complete with bluish-purple blossoms.
Common Flowering Weeds
Queen Anne's lace is a common roadside weed that has an intricate off-white flower that develops by July in most areas. The flat-topped cluster of smaller flowers comprises the flower head and typically contains one small purple blossom in its very center. Milkweed is a common plant that attracts many insects, including butterflies, to its broad red and purple flower clusters. These eventually change into the familiar pods that contain the tiny seeds attached to a tuft of hair that floats about in the breeze during the fall. The white flowers of jimsonweed are a common sight in cow pastures in much of the United States; the plant also goes by the name devil's trumpet and stinkweed, references to the flower's shape and the plant's odor. Some mulleins, thick-stemmed weeds with coarse leaves containing small yellow flowers that grow up and down their stalks, will grow 7 feet tall.
Other Flowering Weeds
Joe-pye weed and boneset are late-summer bloomers that produce a purplish flower head. The goldenrod family has as many as 125 species, according to the book "Weeds," with most plants growing in North America. Goldenrod has yellow flowers that are quite pretty, but the plant grows densely in fields and causes hay fever among allergy sufferers. Thistles such as the Canada thistle spread in patches and are a serious weed, but birds, goldfinches in particular, feast on the seeds that their purple flowers produce. Many weeds double as wildflowers, such as fleabane, chicory, asters, black-eyed Susans, yarrow, hawkweed, sunflowers and Venus' looking-glass.