Native to the western United States, and found from Alaska to Mexico and from the Rocky Mountains to the west coast, in many locations below 10,000 altitude.
This plant sometimes is an annual but more commonly a short-lived perennial, and may spread via stolons or creeping rootstocks. Reproduction is from seeds and flowering occurs early in the spring, continuing through the summer in wet locations.
Plants are semi-aquatic, growing best in very wet situations such as drainage ditches or irrigation canals where they grow at waterline. They are showy, beautiful spring flowers, but can grown in such abundance in irrigation canals that they disrupt the flow of the water.
Mature plants may grow as tall as 3 feet, on either erect stems or with stems lying close to the soil and rising at their ends. These prostrate stems and those that grow in the water will form roots at the nodes. Leaves are opposite, oval, and rounded at the tip and with slightly toothed margins. Lower leaves are larger and have short stalks.
Flowers are large and very showy, with bright yellow petals attached at their bases to form a funnel shape, with the throat of the tunnel spotted with bright red spots and lined with hairy ridges. The seed pod that forms is flattened and oval with two cells, each with numerous seeds inside.
Characteristicts Important to Control:
Plants are dependent on very wet soils.