Illustration of ragweed
: any of various chiefly North American weedy composite herbs (genus Ambrosia) that produce highly allergenic pollen
Examples of ragweed in a Sentence
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The time of day is also important; tree and grass pollens usually accumulate in the evening, while ragweed pollen counts are highest in the morning.
—
Mark Gurarie, Verywell Health, 15 May 2026
As climate change delays the first winter frosts across much of North America, summer ragweed also keeps flowering longer, extending the latter part of pollen season into the fall, said David Wees, a faculty lecturer in horticulture at McGill University in Montreal.
—Keerti Gopal, ArsTechnica, 8 May 2026
These plants include ragweed, daisies, marigolds and chrysanthemums.
—Bestreviews, Chicago Tribune, 14 Apr. 2026
Tree pollen is the first culprit to start causing symptoms, followed by grass pollination later in the spring and summer and ragweed in the late summer and fall.
—Joe Mutascio, IndyStar, 1 Apr. 2026
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Mark Gurarie, Verywell Health, 15 May 2026
As climate change delays the first winter frosts across much of North America, summer ragweed also keeps flowering longer, extending the latter part of pollen season into the fall, said David Wees, a faculty lecturer in horticulture at McGill University in Montreal.
—Keerti Gopal, ArsTechnica, 8 May 2026
These plants include ragweed, daisies, marigolds and chrysanthemums.
—Bestreviews, Chicago Tribune, 14 Apr. 2026
Tree pollen is the first culprit to start causing symptoms, followed by grass pollination later in the spring and summer and ragweed in the late summer and fall.
—Joe Mutascio, IndyStar, 1 Apr. 2026
See All Example Sentences for ragweed
Cite this Entry
“Ragweed.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ragweed. Accessed 20 May. 2026.
Copy CitationKids Definition
ragweed
noun
rag·weed
ˈrag-ˌwēd 
: any of various chiefly North American weedy herbs related to the daisies and producing pollen irritating to the eyes and noses of some persons
Medical Definition
ragweed
noun
rag·weed
ˈrag-ˌwēd
: any of various chiefly North American weedy herbaceous plants comprising the genus Ambrosia and producing highly allergenic pollen responsible for much hay fever and asthma: as
a
: an annual weed (A. artemisiifolia) with finely divided foliage that is common on open or cultivated ground in much of North America
b
: a coarse annual (A. trifida) with some or all of the leaves usually deeply and palmately 3-cleft or 5-cleft
called also great ragweed
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