HEBERLING LAB

  • Welcome
  • People
  • Publications
  • Photos
  • Collected on this day!
  • Welcome
  • People
  • Publications
  • Photos
  • Collected on this day!

Collected on this day...

a weekly blog featuring specimens in the Carnegie Museum herbarium.
Each specimen has an important scientific and cultural story to tell.
This material is based upon work supported by the National Science Foundation grant no. DBI 1612079 (2017-2019) and DBI 1801022 (2019-2022). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

July 14, 1990: 28 years ago

7/14/2018

Comments

 
Picture
​​“This is, perhaps, the most execrable weed that has yet invaded the farms of our country.” 
William Darlington (1859) American Weeds and Useful plants, 2nd ed. 
 
This “execrable weed” described in the quote above by Darlington over 150 years ago was Canada thistle, Cirsium arvense (sunflower family; Asteraceae).
 
This particular specimen of Canada thistle was collected by Walter Zanol on July 14, 1990 near Tarentum, Pennsylvania (Allegheny county). 
 
Canada thistle is a common weed in agricultural fields, disturbed areas, and roadsides in Pennsylvania and across the world.  Although the common name suggests it is from Canada, this is misleading, as the species is from southeastern Europe and eastern Mediterranean.
 
It was among the earliest introduced plant species in North America by European colonists, with records suggesting as early as the 1600s.  It was probably introduced accidentally as a contaminant in crop seed.  It has since spread and become invasive in many US states and Canadian provinces. It remains a major agricultural pest today.
 
By 1851, it was already regarded a “most troublesome [sic] weed, which is extremely difficult to eradicate” in Pennsylvania (Knoll, 1851).
 
It is a weed of many major crops, causing economic harm through reduction of crop yields.  It spreads both sexually (through seeds) and asexually (through underground rhizomes).  It is not uncommon to see many individuals of this species forming dense patches in fields or along the road.  These patches are likely connected belowground (or once were connected).  Because of this attribute of spreading via creeping lateral roots, it is also known as “creeping thistle.”
 
Its purple flowers and spiny stems/leaves are similar at first glance to many thistles, but its horizontal, creeping lateral roots make this species easily distinguishable from the many other non-native and native thistles in Pennsylvania.
 
Keep an eye out for this species.  It can be spotted throughout Pennsylvania this time of year, often forming dense stands that are going to seed.  Their seeds go airborne, looking almost like snow or cotton flying through the air.

 
Comments

    RSS Feed

      Suggest a specimen!

      Your birthday, favorite species, collected by your house, a particular collector, etc...?
      [object Object]
    Submit

    Archives

    October 2022
    April 2022
    January 2022
    December 2021
    November 2021
    October 2021
    August 2021
    July 2021
    June 2021
    May 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017

    Categories

    All
    Amaryllidaceae
    Anacardiaceae
    Apiaceae
    Apocynaceae
    Aquifoliaceae
    Araceae
    Araliaceae
    Asparagaceae
    Asteraceae
    Balsaminaceae
    Betulaceae
    Boraginaceae
    Brassicaceae
    Cactaceae
    Caprifoliaceae
    Caricaceae
    Caryophyllaceae
    Celastraceae
    Climate Change
    Convolvulaceae
    Cornaceae
    Cucurbitaceae
    Cultivated
    Cupressaceae
    Dioscoreaceae
    Dryopteridaceae
    Ericaceae
    Euphorbiaceae
    Fabaceae
    Fagaceae
    Geraniaceae
    Hamamelidaceae
    Holiday Posts
    Introduced Species
    Lamiaceae
    Lauraceae
    Life History Series
    Liliaceae
    Limnanthaceae
    Lycopodiaceae
    Magnoliaceae
    Malvaceae
    Melanthiaceae
    Melastomataceae
    Montiaceae
    Myristicaceae
    Oleaceae
    Onagraceae
    Orobanchaceae
    Oxalidaceae
    Papaveraceae
    Paulowniaceae
    Pinaceae
    Plantaginaceae
    Plants Of The Anthropocene
    Poaceae
    Poisonous
    Polemoniaceae
    Polygonaceae
    Primulaceae
    Pteridaceae
    Ranunculaceae
    Recollected
    Recollection
    Rhamnaceae
    Rosaceae
    Rubiaceae
    Salicaceae
    Santalaceae
    Sapindaceae
    Scrophulariaceae
    Simaroubaceae
    Solanaceae
    Staphyleaceae
    Type Specimens
    Ulmaceae
    Undetermined
    Urban Plants
    Violaceae
    Vitaceae