Skip to content

A Comprehensive Guide to Rough-Stem Rosinweed (Silphium radula)

Rough-Stem Rosinweed (Silphium radula) is a herbaceous perennial that is native to the midwestern United States and the province of Ontario in Canada. This plant is a host to two species of moth and a butterfly and is an important nectar source for other insects. Growing from 1 to 10 feet tall, this species grows in open areas such prairies and roadsides. The yellow flowers bloom from July to September and the plant is hardy in zones 3-9.

Taxonomy and Naming of Rough-stem Rosinweed (Silphium radula)

Herbarium specimen of rough-stem rosinweed (Silphium radula).
Herbarium Specimen — Silphium radula var. radula collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)

Taxonomy

Rough-stem Rosinweed (Silphium radula) was named and described by Thomas Nuttall, an American botanist, in 1840. It still has the same name and is a member of the Aster Family (Asteraceae).

Varieties

This species has two varieties:

  • var. gracile: has 12-18 ray florets
  • var. radula: has > 20 ray florets

Meaning of the Scientific and Common Names

Scientific Name

The genus name, Silphium, is derived from a Greek word that originated from a resin-bearing plant (Missouri Botanical Garden). The species name, radula, is Latin for teeth.

Common Name and Alternative Names

The common name derives from the rough-stem of the plant. Another name in use is rough-leaved rosinweed (Ladd and Thomas 2015).

Physical Description

Yellow flowers of rough-stem rosinweed (Silphium radula).
Flowers of Rough-stem Rosinweed — Public Domain Image
  • Plant Type: This plant is a herbaceous perennial.
  • Height: 1 to 10 feet tall
  • Stem: The stems are erect, terete, and hirsute to scabrous (Flora of North America).
  • Leaves: The leaves are opposite to alternate, petiolate, lanceolate to ovate, and have dentate (lower) to entire margins (Flora of North America). The leaves are 1 to 9 inches long and 0.2 to 3 inches wide.
  • Flower color: yellow
  • Blooming period: This plant blooms from July to September.
  • Fruiting type and period: This plant has achenes that mature in the late fall and winter.

Range of Rough-stem Rosinweed in the United States and Canada

Range map of rough-stem rosinweed (Silphium radula) in the United States and Canada.
Range Map Credit: Kartesz, J.T., The Biota of North America Program (BONAP). 2023.(website https://bonap.org/). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2023. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]

This species is native in the mid-western and south-central United States. There are two varieties, var. gracile, which is native to Texas and adventive in Louisiana, and var. radula, which is native to all of the states shown. Variety radula is considered to be rare in the states of Kansas and Missouri.

Habitat

Prairie habitat in United States.
Prairie Habitat — USFWS Mountain-Prairie, Public domain, via Wikimedia Commons

This species grows in open areas such as prairies and roadsides (Neill and Wilson 2001), and riparian corridors (Hansen 2010).

Hosted Insects

Silphium borer moth (Papaimea silphii) on beige background.
Silphium Borer Moth — Papaipema silphii Bird, 1915 observed in United States of America by Matt Kenne (licensed under CC0 1.0)

The members of the Silphium genus are hosts to the bordered patch (Chlosyne lacinia) butterfly in the western United States and the silphius borer moth (Papaipema silphii) throughout.

Other Supported Wildlife

Honeybee on purple flower.
Purple Aster with Honeybee — John Severns (Severnjc), Public domain, via Wikimedia Commons

This species is an important nectar source to other butterflies, skippers, bees, and wasps.

Frequently Asked Questions

Does this plant have any ethnobotanical uses?

The Native American Ethobotanical Database does not specifically list this species but other species in the genus have been used as pharmaceuticals and foods.

How is this plant distinguished from other Rosinweeds (Silphium spp.)?

The presence of alternate leaves and the spreading phyllaries serve to separate this species from others in the genus (Weakley, et al 2022), especially the entire-leaf rosinweed (Silphium intergrifolium). It can also be separated from S. integrifolium by the longer stem pubescence (Wikipedia).

Is this plant invasive?

This plant has not been noted as being invasvise.

Does this species appear like any other species?

The basal rosette of this species looks similar to Rumex crispa but S. radula has rough leaves, while Rumex has smooth leaves (Plants of Louisiana-USGS)

Gardening with Rough-Stem Rosinweed

Add Rough-Stem Rosinweed to Your Garden

The link below takes you to our product page where we get a small commission from your purchase as no additional cost to you.

Plants of rough-stem rosinweed (Silphium radula) in a prairie.
Rough-stem Rosinweed (Silphium radula) in a field — Eric Hunt, CC BY-SA 4.0, via Wikimedia Commons

Hardiness

This species is hardy in zones 3-9. If your garden is within these zones and you have the right growing conditions (soil, moisture and exposure), you may well be able to grow this plant. However, if planted outside of its range, the hosted species may not recognize the plant or be harmed by ingesting a different species with an unfamiliar chemical composition. For instance, only part of the range of the species overlaps with the bordered patch butterfly. This butterfly would not be benefited by those plants in the east.

Optimal Conditions

This species grows in full sun and prefers dry to medium well-drained soil, but can handle moist soil.

References

  • Hansen, Laura L. 2010. Annotated Checklist of the Vascular Plants of Fort Hood, Texas. Journal of the Botanical Research Institute of Texas 4: 523-558.
  • Ladd, Douglas and Justin R. Thomas. 2015. Ecological checklist of the Missouri flora for Floristic Quality Assessment. Phytoneuron 2015-12: 1-274.
  • Neill, Amanda K. and Hugh D. Wilson. 2001. The Vascular Flora of Madison County, Texas. Sida 19: 1083-1121.
  • Weakley, A.S., and the Southeastern Flora Team. 2022. Flora of the Southeastern United States. University of North Carolina Herbarium, North Carolina Botanical Garden.
Share this post on social!

Leave a Reply

Your email address will not be published. Required fields are marked *

5 × four =

Robert Coxe

Robert Coxe

Robert Coxe is a professional ecologist and botanist who has worked as the State Ecologist of Delaware and as an ecologist for the Western Pennsylvania Conservancy. He is also a former Past-President of the Pennsylvania Academy of Science. He currently is an innkeeper at McMullen House Bed & Breakfast LLC and a web designer and owner for Silphium Design LLC.

The owner of this website has made a commitment to accessibility and inclusion, please report any problems that you encounter using the contact form on this website. This site uses the WP ADA Compliance Check plugin to enhance accessibility.