The handsome violet-blue flower spikes of pickerel weed stand out vividly at the edges of ponds. One of our few blue-flowering pond plants, pickerel weed is easy to identify just by its color and habitat.
The leaves are glossy green, heart-shaped or lance-shaped, and grow in a rosette from a thick rootstock buried in the mud. The leaf veins are many, small, uniformly sized, and parallel.
The flowering stem bears a single leaf and a terminal spike crowded with small, two-lipped blue flowers. Although each flower lasts only one day, the spike blooms from the bottom to top as it grows; therefore, it produces flowers for many weeks. The flowers typically open up in the morning and close in the afternoon. Flowers June–October. As the seeds mature, the stem droops and the seed head hangs just above the water, where the seeds will fall.
Pickerel weed spreads both by rhizome growth and by seed. Seeds have prominent toothed ridges.
Similar species:
When not in flower, pickerel weed may be confused with some species of arrowhead plants (Sagittaria spp.), because of the similar foliage. Note, however, pickerel weed’s rounded basal leaf lobes, while those of potentially confusing arrowhead plants are sharper: arrowhead or halberd shaped.
Water hyacinth (P. crassipes), a relative of pickerel weed, is a nonnative invasive floating aquatic plant. It is in the same genus but the plants are much smaller, only about a foot above the water. A native of South America’s Amazon basin, it causes huge problems in North American southern states, where its tremendous mats choke waterways, killing fish and making it impossible for boats to navigate. It is an extremely fast-growing plant that quickly gets out of control; it is not recommended for Missouri water gardens.
Other relatives of pickerel weed include our native mud plantains (Heteranthera spp.), but these small plants are unlikely to be confused with pickerel weed.
Powdery thalia, or water canna (Thalia dealbata) is another pond-edge emergent plant with showy leaves, but it is much bigger (easily to 6 feet tall), and its leaves are oval or lance-shaped. The veins in its leaves run perpendicular to the leaf midrib. Also, its purple flowers are in looser, more open clusters. It is native to Missouri’s Bootheel but may be planted as a pond ornamental statewide.
Height: usually 2–4 feet.
Cultivated statewide as a pond ornamental. As a Missouri native, distribution is scattered statewide. Some Missouri populations may have arisen as escapes from cultivation.
Habitat and Conservation
Grows on muddy shorelines of ponds and lakes, especially along the edges and in the shallow waters of ponds, swamps, and slow streams, where it often forms dense colonies.
Status
Native wildflower valued as an ornamental pond plant.
Human Connections
Pickerel weed has bold, shiny leaves and attractive blue flowers, is hardy, and is not particularly aggressive, so it has great value as a native ornamental pond or wetland plant in Missouri. It may also be grown in large plant containers.
Pickerel weed has been planted in artificial wetlands designed as biological filters for treating sewage effluent.
The ripe fruits are edible raw, they may be dried and eaten as a snack or mixed in with dry cereals, they may be cooked in water like rice, or they may be dried and ground into a flour. In springtime, the young unfurled leaves and shoots may be cooked as a green vegetable. When very young, the leaves may be eaten raw as a salad green.
Otto Fajen had a distinguished career as a fisheries biologist at MDC for 30 years. In his retirement, he deeply enjoyed the magnificent patch of pickerel weed he had cultivated on his farm pond. “It’s a very beautiful plant, and it doesn’t take over a pond like the water lilies do.”
Ecosystem Connections
Like other plants that colonize the edges of ponds, marshes, lakes, and streams, pickerel weed helps stabilize soil and prevent erosion. It and other emergent aquatic plants provide valuable habitat for a wide range of aquatic, amphibious, and water-loving land animals. Fish and frogs hide in the water at the base of these plants. Dragonflies and damselflies deposit their eggs low on the stalks. Bitterns and other small herons skulk around these plants while red-winged blackbirds, swamp sparrows, and common yellowthroats fly just above the flower clusters. In the Bootheel, green treefrogs explore the leaves and stalks, hunting for insects.
The seeds and rootstocks are important foods for waterfowl, muskrats, and beaver. Muskrats and deer browse the foliage.
The two bright yellow spots on the upper lip of the flowers help guide bees to the center of the flower, making pollination more efficient. Bumblebees are frequent visitors. At least two types of bees, the pickerelweed long-horned bee (Melissodes apicatus) and the pickerelweed shortface (Dufourea novaeangliae), are essentially limited to visiting pickerel weed: they must feed pickerel weed pollen to their young.
A variety of butterflies visit the flowers of pickerel weed for nectar.
Insects that eat the plants leaves, stems, or rhizomes include the pickerelweed borer moth (Bellura densa) and the cattail borer (B. obliqua), both noctuid moths whose larvae tunnel into the plant as they eat. An aquatic leaf beetle, Donacia rugosa, also specially relies on pickerel weed as a host plant. Moths and beetles are eaten by larger animals such as birds, bats, and other vertebrates.
