Lysimachia is a genus of flowering plants that is classified as a member of the family Primulaceae. This genus is, however, part of the Myrsinaceae family according to a molecular phylogenetic study. As of 2010, the genus is composed of 17 species, most of which are called loosestrife. Most species grow yellow flowers, while others grow white ones. The plants reach a height of 3 feet (0.9 m) and have greenish-yellow leaves that develop during mid-summer.
Most plants in this genus are hardy and tender, such as the dwarf varieties like Lysimachia japonica. To help the plants thrive, fertile soil with adequate drainage is important, along with partially shaded sun. The plants grow in damp conditions and are thus found commonly in the subtropical regions of the northern hemisphere or in swampy terrains. These plants are perennials and annuals that have a tendency to become invasive.
Some species of Lysimachia are grown as back borders or margins by some gardeners. One such species is Lysimachia ciliata, commonly named fringed loosestrife, which has also been given the Award of Garden Merit (AGM) by the British Royal Horticultural Society. Lysimachia nummularia, or the creeping jenny, is another species commonly cultivated, along with Lysimachia clethroides, or gooseneck loosestrife, which is a Japanese variety. All varieties are invasive weeds and require care and vigilance to prevent them from spreading. It is possible to prevent their spread by simply pulling up new sprouts.
These flowering plants are mainly used in vases, hanging baskets, or to cover banks. Due to the rapid spread of the plants, they have become a preferred carpeting plant for some gardeners, who grow them under the shade of trees. These plants prefer to grow near bodies of water, but they are also suitable for rock gardens. Another use of these plants is as a food source for the larvae of the dot moth, grey pug, and a few other butterflies and moths.
Plants in the Lysimachia genus are edible and toxin-free. It is believed by some that these sweet and salty flavored herbs work their way into the liver, kidney, and urinary bladder to treat jaundice, urinary calculus, and stranguria. Another medicinal use it has is that it can be externally applied to treat sores, infections, and poisonous snakebites. The herb is usually sold in a pouch as a quick-dissolving granule, with instructions on how to make it into a tea, though it can be applied externally as well.