ragweed

plural ragweeds

1. countableuncountableA plant of the genus Ambrosia, native to North America and a common invasive species elsewhere, particularly noted for producing pollen that triggers hay fever.First known use 1790

   RAGWEED (Jeffogia Fingerolia) : The hayfever king, ragweed, brings tears to the eyes of grown men.

   2009 January 29, “The Leafs' Garden of Weedin'”, in Toronto Star

   1 more example

   Fig. 1.—Spiculated pollens of ragweeds (ambrosias) low in protein. […] In the cocklebur (Xanthium americanum) and the rough wild elder (Iva ciliata), the spicules are shorter, being 0.7 and 0.5 microns, and the reaction is proportionately less active than with the ragweeds (ambrosias). […] While the grass pollens have so light a coat that they are frequently crushed in the ordinary process of mounting, the ragweed (ambrosias) pollen grains resist pressure between two glass slides carried to the point of crushing the glass.

   1916 September 16, W[illiam] Scheppegrell, “Direct and Indirect Hay-Fever: Preliminary Report of the Research Department of the American Hay-Fever-Prevention Association on the Etiology of Hay-Fever”, in George H[enry] Simmons, editor, The Journal of the American Medical Association, volume LXVII, number 12, Chicago, Ill.: American Medical Association, pages 862–863

   Synonyms: ambrosia

2. IrelandScotlandcountableuncountableSynonym of ragwort.First known use 1610

   The fields, being rough and stony, and wholly unfit for the plough, were mostly devoted to the pasturing of sheep and cattle; […] and in many of the inclosures, ragweeds and rushes usurped supremacy over the scanty herbage : but these were not my property.

   1848, Anne Brontë, The Tenant of Wildfell Hall, page 16

   Synonyms: ragwort

3. countableuncountableA summer cypress, mock cypress (Bassia scoparia).