Plant of the Week
Yellow Marsh Marigold (Caltha palustris L.)
By Sue Trull
Marsh marigold is a perennial herb in the buttercup family (Ranunculaceae). Also known as cowslip, cowflock, or kingcup, it is a lovely harbinger of spring. As its name suggests, marsh marigold is a plant of wet places such as marshes, fens, ditches, wet woods, swamps. Indeed, the Latin species epithet, "palustris" refers to "swampy, marshy, or of wet places". Marsh marigold prefers full sun to light shade. Marsh marigold can grow from about 8 inches to about 24 inches tall.
Marsh marigold has glossy green basal leaves that are round, oval, heart or kidney-shaped. The leaves have a deep and narrow sinus or notch. The leaves may have smooth margins or small scallops or teeth along the edges. The basal leaves have long petioles while upper, stem leaves are alternate and on shorter petioles. The plant stems are hollow.
Flowers typically occur in mid-April through June, depending on location, with flowering starting later in the northern parts of the plant's range. Flowers are showy, shiny yellow, about ½ to 1½ inch across, occurring in clusters. They have 5 to 9 petal-like sepals. While these "petals" appear all yellow to humans, to insects, the upper part appears as a mixture of yellow and an ultraviolet color, "bee's purple", while the lower part is all yellow. The flowers have 50 to over 100 stamens. The flowers offer pollen and nectar to insect visitors, and are most commonly pollinated by hoverflies (Syrphidae).
While parts of the plant are used medicinally, handling the plant can cause skin irritation, and uncooked parts are toxic to human consumption. This is due to irritant yellow oil called protoanemonin. Cattle and horses are also poisoned by consuming marsh marigold, although dried plants in hay are no longer toxic to them.
This showy plant is used in landscaping and plants can be obtained commercially. Plants also can be propagated from fresh seed or by dividing mature plants.
Marsh marigold is often common, forming extensive swaths of yellow and deep green. However, it is listed as endangered in Tennessee, at the southern end of its range.