compass plant

Silphium laciniatum L. 

Alternate Common Names: compass plant, rosinweed, turpentine plant, polar plant, pilot-weed

Scientific Synonym: Silphium laciniatum var. robinsonii L. M. Perry

Family: ‌aster family (Asteraceae)

Functional Group: forbs (wildflowers)

Description 

Life cycle and growth form

Perennial, large 15 ft central taproot.

Height: 3-10 ft  

Leaves and stem

Leaves alternate, 12 - 24 in long, deeply lobed, densely covered in coarse hairs; stems are rounded in cross section and covered in long, coarse, spreading hairs, somewhat woody late in the season.

Flower, fruit and seedhead

Flower: Yellow composite flower heads, 3-4 in diameter, several per flowering stem.

Fruit/seedhead: Seeds (technically achenes) form only from outer fertile flowers of the central disk.

Pollination: Primarily bees

Seed

 

Appendix D

‌Seed characteristics 

Seed weight: 

Seeds per ounce: 660 (IA NRCS)

1000 seed weight: 78.05 g (Seed Information Database)

Description: ‘Seeds’ are flat fruits (achenes), 3/8 – 1/2 in long, with a broad wing around margins, making it difficult to get a good separation between filled and unfilled seed. No plume.

Typical seed test 

PLS: 85% (n = 11)

Purity: 88% (n = 11)

Germination: 14% (n = 9)

Dormant: 73% (n = 10)

(averages obtained from n tests of purchased seed lots)

Habitat and range

‌Habitat: Wet-mesic to dry-mesic soil conditions; full sun; typically on high quality prairie remnants, railroads, roadsides, glades, savannas; preference is for moist, well-drained soils for seed production.

Conservation status: Global- G5, secure; Colorado- SH, possibly extirpated; Ohio, Oklahoma, and Virginia- S1, critically imperiled; Michigan- S1/S2, critically imperiled to imperiled; Kentucky and Tennessee- S2, imperiled; South Dakota- S3, vulnerable (NatureServe) 

General Comments

Compass plant is a long-lived, tap-rooted species. An individual seedling may take 2-4 years to flower in production, and flower every year thereafter for a few years. In a prairie, an individual may take 5-10 years to flower, and subsequently flower every other year or so. Silphium species (congeners) will hybridize with one another in nature, so they should be properly isolated from related species for seed production purposes (i.e. cupplant, Silphium perfoliatum; rosinweed, Silphium integrifolium; prairie dock, Silphium terebinthinaceum; etc.) (Fisher 1966, Clevinger and Panero 2000)

Recommendations for Seed Production 

Establishment for seed production

‌Direct seeding

Not recommended for this species

 

‌‌Greenhouse

Seed pre-treatment: Wet stratify 8-12 weeks at 40° F.

Sowing: Sow seed in greenhouse two months before last frost free date.

Transplanting: Transplant into bare soil in rows or weed barrier at 12 in intervals after all danger of frost is past.

‌Appendix A

Stand management

Weeds: Post emergence grass herbicide, tillage, hand roguing. Plastic mulch is not recommended for this species. In an informal trial at TPC, seedlings grown in plastic mulch grew more slowly and took longer to reach maturity than seedlings grown in a biodegradable paper mulch.

Pests: None noted.

Diseases: None noted.

Hybridization risk: This species is known to hybridize with related species Silphium integrifolium, S. perfoliatum, and S. terebinthinaceum. Plan plot layouts to maximize separation among these species.

Seed production

First harvest: Some flowering and seed set end of second year, most will flower during the third growing season from greenhouse grown transplants.

Yield: 40-130 bulk pounds/acre

Stand life: Peak harvests third year. Plants are very long-lived, but seed production may decline significantly in the fourth to fifth year after planting. Harvests from TPC plots also provide some evidence for fluctuating yields over time.

Flowering date: Early July to mid-August.

Seed maturity/Harvest date: Mid-August to mid-September.

Seed retention: Shattering occurs as seeds mature and dry, end of August into September.

Harvest date range at TPC (2003-2012): Aug 22 - Oct 14

Recommended harvest method: Hand collect as seed ripens for most efficient harvest of small plots, combine for larger stands when seed is mostly mature and before significant shattering. 

Appendix B

Seed cleaning and storage

Cleaning process: Pre-clean air-dried material by scalping through 1/2 in mesh and sifting through 1/4 in mesh (most seed will be retained on top of 1/4 in mesh). Brushing with soft bristles helps to break up inert matter to achieve better separation. Air-screen repeatedly to clean.

Seed storage: cool/dry (33-50° F, 30-50% RH)

Appendix C

Released Germplasm 

Source Identified material: Natural Selections/Iowa Ecotype Project Zone 1 (northern Iowa), Zone 2 (central Iowa), and Zone 3 (southern Iowa)

References

Chayka, K. (n.d.). Silphium laciniatum (compass plant). Minnesota Wildflowers. https://www.minnesotawildflowers.info/flower/compass-plant 

Clevinger, J. A. (2020, November 5). Silphium laciniatum Linnaeus. Flora of North America. http://floranorthamerica.org/Silphium_laciniatum 

Hilty, J. (2019). Compass plant - Silphium laciniatum. Illinois Wildflowers. https://www.illinoiswildflowers.info/prairie/plantx/compassx.htm

Houseal, G. A. (2007). Forbs wildflowers. In G. A. Houseal (Eds.), Tallgrass Prairie Center’s native seed production manual (pp. 50–51). Tallgrass Prairie Center - University of Northern Iowa.

Kartesz, J.T., The Biota of North America Program (BONAP). 2023. North American Plant Atlas. (http://bonap.net/napa). 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)]

NatureServe. 2024. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. (Accessed: February 29, 2024).

Runkel, S. T., & Roosa, D. M. (2009). Compass plant. In Wildflowers of the tallgrass prairie: The upper Midwest (2nd ed., pp. 180–181). University of Iowa Press.

USDA NRCS National Plant Data Team. (n.d.). Silphium laciniatum L. USDA plants database. https://plants.usda.gov/home/plantProfile?symbol=SILA3

Species Guide Updated 12/10/2025