Silphium

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Published on: Aug. 2, 2000

Last revision: Nov. 5, 2010

plant grows most often in moist or wet ditches, swales or wetland or stream borders.

Compass plant - Silphium laciniatum

Like a ship's mast in a teeming sea of prairie plants, compass plant stalks-often 10 or more feet tall-are unmistakable prairie landmarks. As John Madson noted in Where the Sky Began, "Pioneers sometimes used compass-plant stalks to mark the edges of wagon routes over the wild prairies-tying scraps of cloth to the tall stems to indicate safe passage around boggy swales and sloughs."

Prairie birds, such as dickcissels, meadowlarks and Henslow's sparrows, like to perch on the tall stalks of compass plants and sing. In late summer and fall, goldfinches and other small birds eat compass plant seeds.

Compass plant leaves are like prairie dock leaves that someone went after with a pair of scissors. Latin for "deeply cut" or "lacerated," the species name, laciniatum, refers to the deeply lobed leaves. The basal leaves are what make this plant memorable: they align themselves in a north-south orientation. This internal compass allows the plant's broad leaves to have maximum exposure to the morning and evening sun and minimal exposure to the hot, drying, direct noon sun.

Rosinweed - Silphium integrifolium

A bit more understated than other Silphium species, rosinweed leaves are about 3 inches long and arranged opposite one another along a purplish green stem. The species name, integrifolium, is Latin for "entire-leaved," referring to the smooth, toothless leaf edges. Rosinweed is a prairie resident that can reach 7 feet tall and often grows in colonies or clusters. Like other Silphium species, rosinweed produces resinous sap and blooms in mid to late summer.

Starry rosinweed - Silphium asteriscus

Greek for "little star," asteriscus most likely refers to this plant's starlike flowers. Known from only 18 southern Missouri counties, starry rosinweed grows on sandy ground, open rocky woods and glades. While it is similar in size and growth habit to rosinweed, starry rosinweed has alternate, rather than opposite, leaves and has fine hairs covering the stems and leaves.

Silphium Specifics

 The Missouri clan of Silphium is small compared to all the members in North America: there are 23 species that range from Florida northwest to the Dakotas and southwest to Texas. Our Silphium species are widespread in Missouri, as well as throughout the Midwest and in southern states.

The genus Silphium is classified by botanists as belonging to the Asteraceae, or sunflower, family.

Including Silphium, the Asteraceae family contains 1,314 genera worldwide and 88 in Missouri. Familiar Asteraceae plants include sunflowers, chrysanthemums, daisies, coneflowers and blazing star. Like these plants, Silphium shares the characteristic of having many flowers in a single head: a sunflower or Silphium blossom is actually composed of numerous individual flowers.

Asteraceae flowers can be bisexual, (containing both male and female reproductive organs) or unisexual (individual flowers with either male or female parts).

What sets Silphium apart from other members of the Asteraceae family is that its ray flowers-the individual flowers around the rim of the flower head with one large yellow petal each-are female, whereas the flowers in the center are male. So seeds of Silphium are produced only around the edge of the flower heads.

In addition, the seeds of Silphium are flattened with wings to help them disperse, unlike many other plants in the Asteraceae family.

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