View source for Silphium laciniatum

{{Short description|Species of flowering plant}}
{{redirect|Compass plant||List of plants known as compass plant}}
{{Speciesbox
|image=Silphium laciniatum Arkansas.jpg
|status=G5
|status_system=TNC
|status_ref=<ref name=ns>[http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Silphium+laciniatum ''Silphium laciniatum''.] NatureServe. 2012.</ref>
|genus=Silphium
|species=laciniatum
|authority=[[Carl Linnaeus|L.]]
}}

'''''Silphium laciniatum''''' is a species of [[flowering plant]] in the family [[Asteraceae]] known commonly as '''compassplant'''<ref>{{PLANTS |id=SILA3 |taxon=Silphium laciniatum |accessdate=15 November 2015}}</ref> or '''compass plant'''. It is native to North America, where it occurs in [[Ontario]] in Canada and the eastern and central United States as far west as [[New Mexico]].<ref name=grin>{{GRIN}}</ref> Other common names include '''prairie compass plant''',<ref name=zh>Zhang, H., et al. (1991). [https://www.jstor.org/discover/10.2307/2996973?uid=3739560&uid=2&uid=4&uid=3739256&sid=21102552761623 Development of leaf orientation in the prairie compass plant, ''Silphium laciniatum'' L.] ''Bulletin of the Torrey Botanical Club'' 118(1) 33-42.</ref> '''pilotweed''', '''polarplant''',<ref name=grin /> '''gum weed''', '''cut-leaf silphium''', and '''turpentine plant'''.<ref name=nrcs>Wynia, R. 2009. [https://plants.usda.gov/factsheet/pdf/fs_sila3.pdf Plant Fact Sheet for compassplant (''Silphium laciniatum'' L.).] USDA NRCS, Kansas Plant Materials Center, Manhattan, Kansas. 2009.</ref> It is a rosinweed of genus ''[[Silphium (genus)|Silphium]]''.

==Description==
[[File:Silphium laciniatum.jpg|thumb|right|Flower head]]
[[File:Silphium laciniatum leaves (9292304354).jpg|thumb|upright|Leaves]]
This plant is a [[taproot]]ed perennial [[herbaceous plant|herb]] producing rough-haired stems usually one to three meters tall. The leaves are variable in shape and size, being {{cvt|4|to|60|cm|frac=4}} long and {{cvt|1|to|30|cm|frac=4}} wide. They are hairy, smooth-edged or toothed, and borne on [[petiole (botany)|petioles]] or not. The back of the [[flower head]] has layers of rough, glandular [[phyllaries]]. The head contains 27 to 38 yellow ray florets and many yellow disc florets. The fruit is a cypsela which can be almost {{cvt|2|cm|frac=4}} long and is tipped with a [[pappus (botany)|pappus]] of two short awns.<ref name=fna>{{eFloras|1|242417267|Silphium laciniatum |tribe=Heliantheae |first=Jennifer A. |last=Clevinger}}</ref>

==Biology==
The common name compass plant was inspired by the "compass orientation"<ref name=zh /> of its leaves.<ref name=nrcs /> The large leaves are held vertically with the tips pointing north or south and the upper and lower surfaces of the blades facing east or west. A newly emerging leaf grows in a random direction, but within two or three weeks it twists on its petiole clockwise or counterclockwise into a vertical position. Studies indicate that the sun's position in the early morning hours influences the twisting orientation.<ref name=zh /> This orientation reduces the amount of solar radiation hitting the leaf surface.<ref name=mobot>[http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/plant-finder/plant-details/kc/f580/silphium-laciniatum.aspx ''Silphium laciniatum''.] Missouri Botanical Garden.</ref> Vertical leaves facing east-west have higher water use efficiency than horizontal or north-south-facing blades.<ref name=jurik>Jurik, T. W., et al. (1990). [https://link.springer.com/article/10.1007/BF00323533#page-1 Ecophysiological consequences of non-random leaf orientation in the prairie compass plant, ''Silphium laciniatum''.] ''Oecologia'' 82(2), 180-86.</ref>

Early settlers on the [[Great Plains]] could make their way in the dark by feeling of the leaves.<ref name=zh />

An early, (if not the earliest) descriptive naming of the compass plant is found in the 1843 hunting trip of William Clark Kennerly,  who upon leaving Westport Kansas in May 1843, observed the plant and began its description in his trip:  "Westward we went, and still westward, through a  flat, arid country with no verdure except the compass plant, which we named for the reason that its large, flat leaves always pointed north and south".{{cn|date=April 2025}}

==Ecology==
Surveys of the insect fauna on typical compass plants have noted many different taxa, often present in large numbers. One plant can produce up to 12 stems. Surveys counted an average of nearly 80 insects on each stem or within its tissues. The vast majority of insects on the stems are the [[gall wasp]]s ''[[Antistrophus rufus]]'' and ''[[Antistrophus minor|A. minor]]'', and the many types of [[parasitoid]]s that attack them.<ref name=took04>Tooker, J. F. and L. M. Hanks. (2004). [http://www.life.illinois.edu/hanks/pdfs/Tooker%20and%20Hanks%202004b.pdf Endophytic insect communities of two prairie perennials (Asteraceae: ''Silphium'' spp.).] ''Biodiversity & Conservation'' 13(13), 2551–66.</ref> The gall wasps, especially ''A. rufus'', inject eggs into the stem, an action that induces the formation of a [[gall]] in the plant tissue. The [[larva]] of the wasp lives and feeds inside the gall, overwinters there, and emerges as an adult the following spring.<ref name=took05>Tooker, J. F., et al. (2005). [http://www.life.illinois.edu/hanks/pdfs/Tooker%20et%20al%202005%20Chemoecology.pdf Plant volatiles are behavioral cues for adult females of the gall wasp ''Antistrophus rufus''.] ''Chemoecology'' 15(2), 85-88.</ref> Over 600 galls can be in a single stem.<ref name=took06>Tooker, J. F. and L. M. Hanks. (2006). [http://www.life.illinois.edu/hanks/pdfs/Tooker%20and%20Hanks%202006.pdf Tritrophic interactions and reproductive fitness of the prairie perennial ''Silphium laciniatum'' Gillette (Asteraceae).] ''Environmental Entomology'' 35(2), 537-45.</ref> The galls are internal in this species, and generally not visible.<ref name=took04 /> The adult female ''A. rufus'' locates an appropriate site to oviposit by detecting [[essential oil|plant volatiles]] emitted by the fresh growing stem of its host plant, a mix of [[monoterpene]]s.<ref name=took05 /> The male ''A. rufus'' also uses the volatiles in his search for mates. Females mate immediately upon emergence from the gall, and the male uses volatiles to find a gall containing a female, as evidenced by the movements of his antennae upon the plant's surface. He then waits there for her to emerge.<ref name=took02>Tooker, J. F., et al. (2002). [http://www.pnas.org/content/99/24/15486.full Altered host plant volatiles are proxies for sex pheromones in the gall wasp ''Antistrophus rufus''.] ''Proceedings of the National Academy of Sciences'' 99(24), 15486-91.</ref>

Other insects found in the plant include several species of [[parasitoid wasp]]s that attack ''A. rufus'' larvae in the galls, the two most common being ''[[Eurytoma luta]]'' and ''[[Ormyrus labotus]]''. Others include ''[[Eupelmus vesicularis]]'' and species of the genera ''[[Brasema]]'' and ''[[Homoporus]]''. The [[beetle]] ''[[Mordellistena aethiops]]'' lives on the plant, its larvae boring into the stems, and it is attacked by parasitoid wasps of the genera ''[[Schizopyramnus]]'', ''[[Heterospilus]]'', and ''[[Tetrastichus]]''.<ref name=took04 />

Many birds and mammals feed on the fruits of the plant. The [[eastern kingbird]] perches on the tall plant to watch for insect prey. [[Livestock]] find it palatable.<ref name=nrcs />

==Uses==
The plant had a variety of uses among [[Indigenous peoples of the Americas|Native American groups]]. The bitter, [[resin]]ous [[plant sap|sap]] could be made into a [[chewing gum]].<ref name=nrcs /><ref name=mobot /><ref name=eth>[http://herb.umd.umich.edu/herb/search.pl?searchstring=Silphium%20laciniatum&searchlimit=100 ''Silphium laciniatum''.] Native American Ethnobotany. University of Michigan, Dearborn.</ref> The [[Pawnee people|Pawnee]] made a [[tisane]] ( herbal tea) with it.<ref name=nrcs /> Many groups burned the dried root as a [[Good luck charm|charm]] during [[lightning]].<ref name=eth />

The plant is cultivated in gardens.<ref name=mobot />

==Literature==
In 1882 [[Benjamin Alvord (mathematician)|Benjamin Alvord]] reviewed the literature on the plant and offered his observations{{what|date=April 2025}}.<ref>{{cite journal |last=Alvord |first=Benjamin |authorlink=Benjamin Alvord (mathematician)
|title=On the Compass Plant |date=1882 |journal=[[American Naturalist]] |volume=16 |issue=8 |jstor=2449634 |pages=625–635 |doi=10.1086/273143|doi-access=free |bibcode=1882ANat...16..625A }}</ref>

In the environmental classic, ''A Sand County Almanac'', [[Aldo Leopold]] devotes much of the July entry to ''Silphium''—its hardiness, but its slow disappearance nevertheless, a harbinger of the fate of the prairie. "It is easy now to predict the future. For a few years my Silphium will try in vain to rise above the mowing machine, and then it will die. With it will die the prairie epoch."{{cn|date=April 2025}}

==References==
{{Reflist}}

==External links==
* {{Commons and category-inline}}
* {{NPIN |link=1}}
* {{Illinois Wildflowers|prairie/plantx/compassx|Silphium laciniatum |link=1}}
* [http://wisplants.uwsp.edu/scripts/Detail.asp?spcode=SILLACvLAC Plants of Wisconsin]
* [http://www.friendsofeloisebutler.org/pages/plants/compassplant.html Plants of the Eloise Butler Wildflower Garden]
* {{Minnesota Wildflowers||flower|compass-plant |link=1}}
* {{PFAF|Silphium laciniatum}}

{{Taxonbar|from=Q1780806}}

[[Category:Silphium (genus)|laciniatum]]
[[Category:Flora of the Eastern United States]]
[[Category:Flora of Ontario]]
[[Category:Flora of New Mexico]]
[[Category:Flora of the United States]]
[[Category:Plants used in traditional Native American medicine]]
[[Category:Plants described in 1753]]
[[Category:Taxa named by Carl Linnaeus]]