ragweeds

Noun

ragweed (countable and uncountable, plural ragweeds)

1. A plant of the genus Ambrosia, native to North America and a common invasive species elsewhere, particularly noted for producing pollen that triggers hay fever.
   • 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...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...

   Synonyms:

   ambrosia

2. (Ireland, Scotland) Synonym of ragwort.
   • 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. A summer cypress, mock cypress (Bassia scoparia).