compass plant

(Silphium laciniatum)

               
Conservation Status

IUCN Red List

not yet assessed

compass plant

NatureServe

NNR - Unranked

SNR - Unranked

Minnesota

not listed

Nativity

Native

Occurrence

Common

Habitat

Dry to moderate moisture. Prairies, railroads, disturbed areas. Full sun.

Flowering

June to September

     
Flower Color

Yellow ray florets, yellow disk florets

     
Height

36 to 80

     

Identification

This is an erect, perennial forb that rises on usually a single stem from a deep, woody taproot that can extend 15 into the soil. It can be 3 to 6½ in height, but is usually no more than 8 tall. It is a long-lived plant, sometimes surviving up to 100 years.

The stem is erect, stout, light green or medium green, round in cross section, and unbranched below the inflorescence. It is moderately covered with relatively long, white hairs and also with minute, usually gland-tipped hairs.

Basal leaves are egg-shaped in outline, 12 to 24 long, and 6 to 12 wide. They are rough to the touch, thick, and leathery. They are deeply cut almost to the midrib into 3 to 15 primary lobes (pinnatifid) which are sometimes again lobed (bipinnatifid). The primary and secondary lobes are oblong to oblong triangular. They taper to a sharp point at the tip and are broadly attached at the base. The upper and lower surfaces are sparsely to moderately covered with spreading hairs and are dotted with scattered, stalkless or impressed glands. The margins are untoothed or may have a few teeth. The axis of the leaf is oriented north and south so that the blade faces east or west, thus avoiding the hot midday sun. Basal leaves are present at flowering time.

Stem leaves are alternate, short-stalked or stalkless, and otherwise similar to basal leaves. They become progressively smaller as they ascend the stem. Upper stem leaves 1½ to 6 long, short-stalked, and once pinnatifid.

The inflorescence is an elongated, usually branched cluster (panicle) of 6 to 30 flower heads at the end of the stem. The flower heads are short-stalked or nearly stalkless.

The flower heads are 2½ to 4 in diameter. The whorl of modified leaves (bracts) at the base of the flower head (involucre) is bell-shaped to hemispheric and to 13 16 in diameter. It is composed of 25 to 45 bracts (phyllaries) in 2 or 3 overlapping series. The phyllaries are egg-shaped, sharply pointed at the tip, ¾ to 19 16 long, and often spreading or bent backward at the tip. They are sparsely to densely hairy and are usually also dotted with glands.

There are 27 to 38 ray florets and 100 to 275 disk florets. The ray florets are yellow, ¾ to 2 long, and fertile. The disk florets are yellow and infertile.

The fruit is a dry, one-seeded seed capsule (cypsela). The cypsela is black to brown, egg-shaped, flattened, to 11 16 long, and ¼ to ½ wide. It is broadly winged and has a deep notch at the tip. There is no tuft of hairs attached to the end.

 
Similar
Species

 


Distribution Distribution Map  

Sources: 2, 3, 4, 5, 7, 28.

The sighting in Stevens County is an outlier. It was at Verlyn Marth Memorial Prairie SNA and may have been introduced when seeding the restored prairie.


Comments

 


Taxonomy

Family:

Asteraceae (aster)

 

Subfamily:

Asteroideae

 

Supertribe:

Helianthodae

 

Tribe:

Heliantheae (sunflower)

 
Synonyms

Silphium laciniatum var. laciniatum

Silphium laciniatum var. robinsonii

 
Common
Names

blackroot

Bowman’s-root

compass plant

compassplant

tall speedwell


 

 

 

 

 

 

 

Glossary

Bipinnatifid

Twice pinnatifid. Cut deeply into lobes with each lobe also cut into deep lobes.

 

Bract

Modified leaf at the base of a flower stalk or flower cluster.

 

Cypsela

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed from the wall of the inferior ovary and also from other tissues derived from the receptacle or hypanthium, does not split open at maturity, but relies on decay or predation to release the contents.

 

Involucre

A whorl of bracts beneath or surrounding a flower or flower cluster.

 

Panicle

A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.

 

Phyllary

An individual bract within the involucre of a plant in the Asteraceae family.

 

Pinnatifid

Deeply cut, more than half way to the midrib but not to the midrib, into lobes that are spaced out along the midrib; the lobes do not form separate leaflets.

 

Wing

A thin, flat, membranous, usually transparent appendage on the margin of a structure.

       

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Flower Head

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Leaves

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Leaves in Early Spring

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Infructescence

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Slideshows

   
  Silphium laciniatum COMPASS PLANT
Frank Mayfield
 
  Silphium laciniatum COMPASS PLANT  

 

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  Rare plant find prompts county to help
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About

Published on Jun 19, 2012

Walter Stewart rushed to check it out and discovered a "sunflower-looking" plant referred to as "silphium laciniatum" or compass plant, first time it has ever been seen in Hays County.

 
     
  OEC Tallgrass Prairie Tour - July 19 - compass plant
Ohio Environmental Council
 
   
 
About

Uploaded on Jul 20, 2008

Guy Denny tells about the history and characteristics of the compass plant.

 
     

 

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