{{Short description|Species of flowering plant}} {{speciesbox |image = Commelina diffusa pollinator Layton 171 XTBG.JPG |image_caption = Flower being visited by a pollinator in Xishuangbanna, Yunnan, China |status = LC |status_system = IUCN3.1 |status_ref = <ref name="iucn status 11 November 2021">{{cite iucn |author=Lansdown, R.V. |date=2018 |title=''Commelina diffusa'' |volume=2018 |article-number=e.T177028A67776407 |doi=10.2305/IUCN.UK.2018-2.RLTS.T177028A67776407.en |access-date=11 November 2021}}</ref> |genus = Commelina |species = diffusa |authority = Burm.f. |subdivision_ranks = Subspecies and varieties |subdivision = *''Commelina diffusa'' subsp. ''diffusa'' *''Commelina diffusa'' var. ''gigas'' {{small|(Small) Faden}} *''Commelina diffusa'' subsp. ''montana'' {{small|J.K.Morton}} *''Commelina diffusa'' var. ''parva'' {{small|Kayama}} *''Commelina diffusa'' subsp. ''violacea'' {{small|Faden}} |subdivision_ref = <ref name = powo>{{cite web |title=''Commelina diffusa'' Burm.f. |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:172020-1 |website=Plants of the World Online |publisher=Royal Botanic Gardens, Kew |access-date=23 March 2026}}</ref> |synonyms={{collapsible list|bullets=true |title=Synonyms of subsp. ''diffusa'' |''Commelina agraria'' {{small|Kunth}} |''Commelina agraria var. prostrata'' {{small|(Kunth) Seub.}} |''Commelina agraria var. repens'' {{small|Seub.}} |''Commelina bangii'' {{small|Rusby}} |''Commelina caespitosa'' {{small|Roxb.}} |''Commelina cajennensis'' {{small|Kunth}} |''Commelina canariensis'' {{small|C.Sm.}} |''Commelina cayennensis'' {{small|Rich.}} |''Commelina communis'' {{small|Walter}} |''Commelina communis'' {{small|Engelm. ex Kunth}} |''Commelina diffusa var. major'' {{small|Kayama}} |''Commelina formosa'' {{small|Graham}} |''Commelina gracilis'' {{small|Ruiz & Pav.}} |''Commelina gracilis var. glabrata'' {{small|C.Presl}} |''Commelina nudiflora f. agraria'' {{small|(Kunth) C.B.Clarke}} |''Commelina nudiflora var. werneana'' {{small|(Hassk.) C.B.Clarke}} |''Commelina obtusifolia'' {{small|Vahl}} |''Commelina ochreata'' {{small|Schauer}} |''Commelina pacifica'' {{small|Vahl}} |''Commelina pilosa'' {{small|Pers.}} |''Commelina pilosula'' {{small|Rich.}} |''Commelina prostrata'' {{small|Poepp.}} |''Commelina prostrata'' {{small|Kunth}} |''Commelina sabatieri'' {{small|C.B.Clarke}} |''Commelina sellowii'' {{small|Schltdl.}} |''Commelina werneana'' {{small|Hassk.}} |''Nephralles parviflora'' {{small|Raf.}} }} |synonyms_ref = <ref name = diffusa>{{cite web |title=''Commelina diffusa'' subsp. ''diffusa'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77169466-1 |website=Plants of the World Online |publisher=Royal Botanic Gardens, Kew |access-date=23 March 2026}}</ref> }}
'''''Commelina diffusa''''', sometimes known as the '''climbing dayflower''' or '''spreading dayflower''', is an herbaceous plant in the dayflower family. Its native distribution is Paleotropical, including tropical and southern Africa, Yemen, the Indian Subcontinent, Indochina, Peninsular Malaysia, southern China, Japan, Korea, the Philippines, New Guinea, and the Pacific Islands. It has been introduced throughout the tropical and subtropical Americas, where it is now found from the eastern and midwestern United States to northern Argentina.<ref name = powo/> It has been introduced to the southeastern United States where it is most common in wet disturbed soils. There are two recognised varieties, one being the type and the other being ''C. diffusa'' var. ''gigas'', which is native to Asia and has been introduced to Florida. It flowers from spring to fall and is most common in disturbed situations, moist places and forests. In China the plant is used medicinally as a febrifuge and a diuretic. A blue dye is also extracted from the flower for paints. In the Hawaiian Islands, it is known as "honohono grass", although it is technically not a grass. "Honohono" refers to the alternating structure of the leaves. At least one publication lists it as an edible plant in New Guinea.
==Description== ''Commelina diffusa'' is typically an annual herb, though it may be perennial in the tropics.<ref name=flora>{{Citation| last =Faden| first =Robert | contribution =Commelina diffusa| year =2006| title =Flora of North America online | volume =22| contribution-url =http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=222000040| place=New York & Oxford| publisher =Oxford University Press}}</ref> It spreads diffusely, creeping along the ground, branching heavily and rooting at the nodes, obtaining stem lengths up to 1 metre. Pubescence on the stem is variable and ranges from glabrous to hispidulous, which can occur either in a line or throughout.<ref name=chinaflora>{{Citation| last =Hong| first =Deyuan |author2=DeFillipps, Robert A.| contribution =Commelina diffusa | year =2000| title =Flora of China| editor-last =Wu| editor-first =Z. Y. |editor2=Raven, P.H. |editor3=Hong, D.Y.| volume =24| page =36| place=Beijing| publisher =Science Press | contribution-url =http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=222000040}}</ref> The leaf blades are relatively variable, ranging from lanceolate to ovate,<ref name=flora/> with proximal leaves tending to be more oblong. They measure 3 to 12 cm in length by 0.8 to 3 cm in width.<ref name=chinaflora/> North American populations tend to have smaller leaf size, typically measuring 1.5 to 5 cm, by 0.5 by 1.8 cm. The leaf apex is acute to acuminate.<ref name=flora/> The leaf surface can be either glabrous (i.e. hairless) or hispid (i.e. bristly). The leaves are subsessile (i.e. having a very small petiole) with a leaf sheath striped with red and covered with hispid pubescence.
The flowers are arranged into cincinni (singular: cincinnus), or scorpioid cymes. This is a form of a monochasium where the lateral branches arise alternately on opposite sides of the false axis. There are typically two cincinni present, with the lower cincinnus bearing 2 to 4 flowers, while the upper cincinnus has one to several flowers. The upper cincinnus is generally exerted on specimens with larger spathes, but it may be included in specimens with smaller spathes.<ref name=flora/> The upper cincinnus bears only male flowers and has a longer peduncle, while the lower cincinnus bears bisexual flowers on a shorter peduncle. The pedicels supporting single flowers, and later the fruits, are thick and curved and measure about 3 to 5 mm. The membranous sepals are inconspicuous at only 3 to 4 mm in length.<ref name=chinaflora/> The petals are blue, though may be lavender in rare cases.<ref name=flora/> The upper two petals measure 4.2 to 6 mm.<ref name=chinaflora/> The anther connective (i.e. the tissue connecting the two halves of the anther) of the centre-most stamen has a broad transverse band of violet. The spathes are solitary, borne on a peduncle and typically falcate (i.e. sickle-shaped) with a cordate (i.e. heart-shaped) to rounded base, acuminate apices and can be either glabrous or hispidulous (i.e. minutely hispid) beneath. They usually measure 0.8 to 2.5 cm long, but may be as short as 0.5 cm and as long as 4 cm. They are typically 0.4 by 1.2 cm wide, but may be up to 1.4 cm long. Their peduncles are usually 0.5 to 2 cm long and rarely up to 2.9 cm.<ref name=flora/><ref name=chinaflora/> Flowering occurs from May to November.<ref name=chinaflora/> Pollens are elongated with bilateral symmetry, approximate size is 73 microns. thumb|Pollens
The fruit is a capsule which has three locules and 2 valves. It measures 4 to 6.3 mm long by 3 to 4 mm wide, though it may be as narrow as 2.1 mm. They contain five brown seeds that are 2 to 2.8, rarely up to 3.2 mm long, by 1.4 to 1.8 mm wide. They are deeply reticulate (i.e. net-like). The chromosome number is 2n = 30.<ref name=flora/>
==Distribution and habitat== ''C. diffusa'' is present in tropical and subtropical locations worldwide. It can be found throughout much of southern temperate and subtropical China, specifically in the provinces of Guangdong, southwestern Guangxi, southwestern Guizhou, Hainan, southeastern Tibet and southeastern Yunnan.<ref name=chinaflora/> Within China, it can be found at sea level up to 2,100 metres (6,889 feet), typically being associated with forests, thickets, stream banks and open, humid habitats.<ref name=chinaflora/>
In Japan, the plant has been reported from Yakushima, off Kyūshū, and is also present in the Ryukyu Islands (from Amami Ōshima southwards).<ref>{{citation| title=Flora of Japan |language=en | last=Ohwi| first=Jisaburo| year=1965| publisher=Smithsonian Institution| location=Washington, D.C.| page=271}}</ref>
In the West Indies, it is a common weed that is especially associated with roadsides, moist ditches and wasteland, where it can be found from sea level to 1,050 metres.<ref name=puerto/> ''C. diffusa'' is originally native to the Caribbean Islands, including much of Puerto Rico and several of the U.S. Virgin Islands (including Saint Croix, Saint Thomas and Tortola).<ref name=puerto>{{citation| last=Acevedo-Rodriguez| first=Pedro |author2=Strong, Mark T.| journal=Contributions of the United States National Herbarium| title=Monocotyledons and Gymnosperms of Puerto Rico and Virgin Islands| volume=52| page=158| year=2005}}</ref>
In the United States, it is also typical of disturbed locations, such as gardens, cultivated areas and lawns, but can also be found in woods, near creeks and other moist, partially-shaded areas.<ref name=flora/> It has been introduced to the eastern and southeastern United States, where it is present from Maryland in the north, west to Missouri and south to Texas and Florida. It has also been introduced to Hawaii, where it is a common and quickly-spreading weed. The variety ''C. diffusa'' var. ''gigas'' has been introduced to Florida. The plant is commonly observed in California, mainly as a seasonal perennial, where it reseeds each fall and reappears in the spring, generally after periods of rain. It is most commonly seen in the Southern Californian counties of Los Angeles, Orange, San Diego, Santa Barbara, and Ventura.<ref name=flora/> Given this distribution, it is likely also present south of the US-Mexico Border, as well.
==Subdivisions== Five subdivisions are accepted:<ref name = powo/> *''Commelina diffusa'' subsp. ''diffusa'' – tropical and Southern Africa, Yemen, Indian Subcontinent, Indochina, southern China, Korea, Japan, Taiwan, Philippines, New Guinea, and the Pacific Islands. Introduced to the Americas.<ref name = diffusa/> *''Commelina diffusa'' var. ''gigas'' {{small|(Small) Faden}} (synonym ''C. gigas'' {{small|Small}}) – native range unknown, likely Asia. Introduced to Florida. *''Commelina diffusa'' subsp. ''montana'' {{small|J.K.Morton}} – Nigeria to Gabon, Rwanda, Uganda, and Kenya *''Commelina diffusa'' var. ''parva'' {{small|Kayama}} – Ryukyu Islands *''Commelina diffusa'' subsp. ''violacea'' {{small|Faden}} – Madagascar
==Uses== Within China, ''Commelina diffusa'' is used as a medicinal herb with febrifugal and diuretic effects. A dye is also obtained from the juice of the petals for use in painting.<ref name=chinaflora/>
Within Hawaii, "honohono grass" was used as medicine to aid with deep cuts. While other Hawaiian herbs just get superficial cuts, honohono grass is an herb to aid with deeper troubling issues.
According to [https://web.archive.org/web/20110927071039/http://www.papuaweb.org/dlib/bk/french/03.pdf a work by Bruce French published on papuaweb.org], the young leaf tips are cooked and eaten in New Guinea. (See page 80.)
==References== {{Reflist}}
==External links== *{{Commons-inline}} * [http://www.missouriplants.com/Bluealt/Commelina_diffusa_page.html Profile at Flora of Missouri Webpage] * [https://web.archive.org/web/20100611042535/http://windward.hawaii.edu/people/Ingelia_White/Honohono_Grass.html Ethnopharmacognosy Series II: Pharmaceutical and Nutraceutical Values of Honohono Grass] {{WestAfricanPlants|Commelina diffusa}}
{{Taxonbar|from=Q5152275}}
diffusa Category:Flora of East Tropical Africa Category:Flora of Northeast Tropical Africa Category:Flora of South Tropical Africa Category:Flora of Southern Africa Category:Flora of West-Central Tropical Africa Category:Flora of West Tropical Africa Category:Flora of Eastern Asia Category:Flora of South-Central China Category:Flora of Southeast China Category:Flora of the Indian subcontinent Category:Flora of Indo-China Category:Flora of Madagascar Category:Flora of Mauritius Category:Flora of the Pacific Category:Flora of Peninsular Malaysia Category:Flora of the Philippines Category:Flora of Tibet Category:Flora of Yemen Category:Least concern flora of Africa Category:Least concern flora of Asia Category:Least concern flora of the Pacific Category:Plants described in 1768 Category:Taxa named by Nicolaas Laurens Burman