{{Short description|Species of flowering plant}} {{Speciesbox |name = ''Tripleurospermum inodorum'' |image = Tripleurospermum perforatum 20041012 2572.jpg |image2 = Tripleurospermum_Perforatum.jpg |taxon = Tripleurospermum inodorum |authority = ([[Carl Linnaeus|L.]]) [[Sch.Bip.]] |synonyms = *''Matricaria inodora'' {{au|L.}} *''Matricaria perforata'' {{au|Mérat}} *''Tripleurospermum perforatum'' {{au|(Mérat) M.Laínz}} * ''Tripleurospermum inodorum'' * ''Matricaria maritima'' subsp. ''inodorum'' * ''Tripleurospermum maritimum'' subsp. ''inodorum'' (L.) Hyl. ex Vaar. |}}
'''''Tripleurospermum inodorum''''', common names '''scentless false mayweed''',<ref>{{PLANTS|id=TRPE21|taxon=Tripleurospermum perforatum|accessdate=15 December 2015}}</ref> '''scentless mayweed''', '''scentless chamomile''', and '''Baldr's brow''', is the [[type species]] of ''[[Tripleurospermum]]''. This plant is native to Eurasia,<ref>{{cite web |title=Tripleurospermum inodorum (L.) Sch.Bip. {{!}} Plants of the World Online {{!}} Kew Science |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:256500-1 |website=Plants of the World Online |access-date=24 September 2024 |language=en}}</ref> and introduced to North America, where it is commonly found in fields, fallow land and gardens.<ref>{{cite web | url = http://www.luontoportti.com/suomi/en/kukkakasvit/scentless-mayweed | title = Scentless Mayweed | work = NatureGate }}</ref>
==Description== [[File:Tripleurospermum inodorum kz04.jpg|thumb|Cotyledons]]
The species may grow to be {{convert|20|–|80|cm|in|abbr=on}} in height. It is usually 1-stemmed, with the stem erect–ascending, branching, glabrous, green. Stems are single, erect, branched in the upper plant, weakly ridged or lined, hairless though sparsely hairy when young.
Leaves are alternate, short-stalked–stalkless. The blade is 2–3 times pinnately lobed (–with leaflets), glabrous, lobes (or leaflets) long, thread-like narrow, sharp-pointed. Leaves are ¾ to 3 inches long, feathery with a few to numerous thread-like branching lobes.<ref name="minnesotawildflowers.info">{{Cite web|url=https://www.minnesotawildflowers.info/flower/scentless-false-mayweed|title=Tripleurospermum inodorum (Scentless False Mayweed): Minnesota Wildflowers|website=www.minnesotawildflowers.info|language=en|access-date=2020-02-03}}</ref> The [[cotyledon]]s are oribicular to oblong, very small, 3 to 5 mm long, and stalkless.<ref>{{Cite web|url=http://biology.burke.washington.edu/herbarium/imagecollection/taxon.php?Taxon=Tripleurospermum%20inodorum|title=Burke Herbarium Image Collection|website=biology.burke.washington.edu|access-date=2020-03-30}}</ref>
Flowers are single flower-like, usually with a {{convert|3|–|5|cm|in|abbr=on}} [[Pseudanthium|capitula]], surrounded by involucral bracts. The capitula's ray-florets are white, tongue-like, tip shallowly 3-toothed; disc florets are yellow, tubular, small. Stamens 5. Pistil of 2 fused carpels. Involucral bracts are of different lengths, {{convert|1|–|1.5|mm|in|abbr=on}} broad, light brown–white margins. Disc is stacked, full. Capitula is 1–20 borne in a corymbose cluster. It flowers from June–October.<ref>{{Cite web|url=http://www.luontoportti.com/suomi/en/kukkakasvit/scentless-mayweed|title=Scentless Mayweed, Tripleurospermum inodorum - Flowers - NatureGate|website=www.luontoportti.com|access-date=2020-02-03}}</ref> Pollen is collected by solitary bees.<ref>{{cite journal|last1=Wood|first1=Thomas J.|last2=Holland|first2=John M.|last3=Goulson|first3=Dave|title=Providing foraging resources for solitary bees on farmland: current schemes for pollinators benefit a limited suite of species|journal=Journal of Applied Ecology|volume=54|pages=323–333|date=2016|doi=10.1111/1365-2664.12718|url=http://sro.sussex.ac.uk/id/eprint/60867/3/Pollen%20insights%20FINAL%20DRAFT%2006.04.2016.pdf}}</ref>
The fruit is a flattish, ridged [[achene]], with 2 round–angular oil spots, tip sometimes with small, membranous ring.
===Similar species=== ''[[Tripleurospermum maritimum]]'' (false mayweed) is morphologically similar to ''T. inodorum''. False mayweed achenes are a similar size, brown colour, and rectangular shape as scentless chamomile. The rib arrangement and the resin glands are also similar to scentless chamomile. False mayweed achenes usually have less space between the ribs, the resin glands cannot be seen from the top of the achene, and the resin glands are often brown and oval rather than round and reddish compared to scentless chamomile.<ref name="Government of Canada">{{Cite web|url=https://inspection.gc.ca/plant-health/seeds/seed-testing-and-grading/seeds-identification/tripleurospermum-inodorum/eng/1405513897968/1405513898734|title=Weed Seed: Tripleurospermum inodorum (Scentless chamomile)|last=Government of Canada|first=Canadian Food Inspection Agency|date=2014-11-06|website=inspection.gc.ca|access-date=2020-02-03}}</ref>
==Taxonomy== Historically included the genus ''[[Matricaria]]'', ''Tripleurospermum inodorum'' has been the subject of some controversy, with many revisions in recent years. The ''[[Flora Europaea]]'' uses ''Matricaria perforata'' for this species. Synonyms/other scientific names include ''Tripleurospermum perforatum'' and ''Tripleurospermum maritimum'' subsp. ''inodorum''.
W. L. Applequist (2002) has shown that the name ''Matricaria inodora'' is not a superfluous new name for ''M. chamomilla'' as earlier stated by S. Rauschert (1974). Therefore, the appropriate name under ''Tripleurospermum'' is ''T. inodorum''. She also considered its type to belong in ''T. maritimum'' and formally recognized it there as subsp. ''inodorum'', on the basis of hybridization with other ''T. maritimum'' subspecies (A. Vaarama 1953); on the same basis, however, Hämet-Ahti maintained the species distinction between ''T. inodorum'' and ''T. maritimum'', while making ''T. phaeocephalum'' a subspecies of the latter.<ref>{{Cite web|url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200024603|title=Tripleurospermum inodorum in Flora of North America @ efloras.org|website=www.efloras.org|access-date=2020-02-03}}</ref>
''Tripleurospermum inodorum'' hybridizes with ''[[Cota tinctoria]]'' to form the hybrid [[× Tripleurocota|× ''Tripleurocota sulfurea'']].<ref name=POWO_77081589-1>{{Cite POWO|title=''× Tripleurocota sulfurea'' (P.Fourn.) Starm..|id=77081589-1|access-date=2023-12-05|mode=cs1}}</ref>
==Ecology== ''T. inodorum'' grows in fields, fallow land, lawns, wasteland, roadsides, yards, gardens. It is an annual or short-lived perennial.<ref name="minnesotawildflowers.info"/> It is native to [[Eurasia]].<ref name="nwcb"/>
''Tripleurospermum inodorum'' has been classified as a noxious weed (class C) in the state of Washington<ref name="nwcb">{{cite web |title=Scentless Mayweed |url=https://www.nwcb.wa.gov/weeds/scentless-mayweed |website=nwcb.wa.gov |publisher=Washington State Noxious Weed Control Board |access-date=27 August 2023}}</ref> and is considered invasive in other states (it is resistant to some herbicides); it is a weed of cereals in western Canada. According to Canadian regulations, it is classified as Secondary Noxious, Class 3 and Noxious, Class 5 in the Canadian ''Weed Seeds Order'', 2016 under the ''Seeds Act''.<ref name="Government of Canada"/>
==Mythology== In [[Sweden]] and [[Norway]], it is called ''[[Baldr]]'s brow'', but in [[Iceland]], it is the close relative [[sea mayweed]] (''Matricaria maritima'') that carries this name.<ref>[http://linnaeus.nrm.se/flora/di/astera/tripl/tripper.html Den virtuella floran (in Swedish)]</ref> In ''[[Gylfaginning]]'', [[Snorri Sturluson]] explains that the name Balder's brow comes from the plants' whiteness: {| | :''Annarr sonr Óðins er Baldr, ok er frá honum gott at segja. Hann er beztr, ok hann lofa allir. Hann er svá fagr álitum ok bjartr, svá at lýsir af honum, ok eitt gras er svá hvítt, at jafnat er til Baldrs brár. Þat er allra grasa hvítast, ok þar eftir máttu marka fegurð hans bæði á hár ok á líki. Hann er vitrastr ásanna ok fegrst talaðr ok líknsamastr, en sú náttúra fylgir honum, at engi má haldast dómr hans. Hann býr þar, sem heitir Breiðablik. Þat er á himni. Í þeim stað má ekki vera óhreint[.]''<ref>[http://www.heimskringla.no/wiki/Gylfaginning An online edition of the Old Norse text.]</ref> | :The second son of [[Odin]] is Baldr, and good things are to be said of him. He is best, and all praise him; he is so fair of feature, and so bright, that light shines from him. A certain herb is so white that it is likened to Baldr's brow; of all grasses it is whitest, and by it thou mayest judge his fairness, both in hair and in body. He is the wisest of the [[Æsir]], and the fairest-spoken and most gracious; and that quality attends him, that none may gainsay his judgments. He dwells in the place called [[Breidablik]], which is in heaven; in that place may nothing unclean be[.]<ref>[http://www.northvegr.org/lore/prose/033036.php ''Brodeur's translation'' in English.]</ref> | |}
==References and footnotes== {{Reflist}}
==External links== {{commons category-inline|Tripleurospermum inodorum}}
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[[Category:Anthemideae]]