Persicaria sagittata (L.) H.Gross, Beih. Bot. Centralbl. 37(2): 113 1919. (Syn: Helxine sagittatum (L.) Raf.; Persicaria sagittata var. sieboldii (Meisn.) Nakai; Persicaria sieboldii (Meisn.) Ohki; Persicaria sieboldii var. brevifolia Kitag.; Polygonum belophyllum Litv.; Polygonum paludosum (Kom.) Kom.; Polygonum sagittatum L.; Polygonum sagittatum var. boreale Meisn.; Polygonum sagittatum var. gracilentum Fernald; Polygonum sagittatum var. paludosum Kom.; Polygonum sagittatum var. sibiricum Meisn.; Polygonum sagittatum var. sieboldii (Meisn.) Maxim. ex Kom.; Polygonum sagittatum subsp. sieboldii (Meisn.) Vorosch.; Polygonum sieboldii Meisn.; Polygonum sieboldii var. pratense Y.L. Chang & S.X. Li; Tasoba sagittata (L.) Raf.; Tracaulon sagittatum (L.) Small; Tracaulon sibiricum (Meisn.) Greene; Tracaulon sieboldii (Meisn.) Greene; Truellum paludosum Soják; Truellum sagittatum (L.) Soják; Truellum sibiricum (Meisn.) Soják; Truellum sieboldii Soják);
Persicaria sagittata, common names American tearthumb, arrowleaf tearthumb, or arrowvine, is a plant species widespread in the eastern half of North America as well as in eastern Asia. It is known from every state and province from Texas to Manitoba to Newfoundland to Florida, plus Colorado and Oregon. It is also reported from China, the Russian Far East, Siberia, Korea, Japan, northern India and Mongolia.
It grows in moist areas along lake shores, stream banks, etc.Persicaria sagittata is an annual herb up to 200 cm tall, with prickles along the stem. Leaves are up to 10 cm long, heart-shaped or arrowhead-shaped (unusual for the genus). Flowers are white to pink, borne in in spherical to elongated clusters up to 15 mm long. 
(From Wikipedia on 28.5.14)
Polygonaceae Fortnight- Polygonum? for id from Gori valley area:: NS May 30 : 11 posts by 5 authors. Attachments (3).
This delicate herb was shot from Gori valley area.. still lies unidentified with me.. tentatively I have placed this under Polygonum
Wondering how this plant missed my attention!
For me this is Persicaria sagittata (L.) H. Gross.. characterized by the sagittate leaves.
Thanks for sharing the beautiful images Sir!
Thanks … for inputs.. thanks … for identification…
Thanks once again …, but how do you explain – “perianth white ….. or red, ….. not becoming blue” as in FoNA, and also absence of at least 5 mm petiole, besides some other points?
Thanks for your efforts … Perianth color is variable and taxonomically less important (at least in Persicaria)…this blue seems to be an intermediate between white and pink. Further we can see the terminal leaves here with no petiole….’ll get them as you go down.
Putting a link for your kind perusal. Hope the confusion will go.
Waiting to hear from you.
Thanks a lot …, I am really grateful for addressing my concern. I put down my explanation (in favour of P, nepalensis) –
I would request you to check Flora of British India also, because there are several var. under P. alatum Ham. and give your final verdict which I will accept whatever it may.
Thanks a lot … for your concerns.
I am happy that you are not blindly following my words. This inquisitiveness makes you different. But anyway, I am going to stick with my ID as the sagittate leaves are very clear in the photographs. Further, I’ve seen P. nepalense many times in field/herbaria but never found the same leaves (as in pics) anywhere. Identity in the links provided by you is correct and they definitely are P. nepalense.
I accept … Thank you very much for spending some time over it.
SK120OCT02-2016:ID : 10 posts by 3 authors. Attachments (9)
Sharing some pictures for ID shot at Chandragiri Hill Kathmandu on 19 September 2016 at 8200 ft.
Could it be Fagopyrum or Persicaria??
Thanks for sharring …
This is interesting! Looks close to Persicaria sagittata (L.) H.Gross. Please share more images of leaf, if you have.
Inserting some pictures as advised.
Yes! It looks like Persicaria sagittata (L.) H. Gross (Polygonaceae) to me.
SK890 07 DEC-2017:ID : 11 posts by 3 authors. Attachments (7)
Location: Ranikot, Bhaktapur, Nepal
Altitude: 6200 ft.
Date: 7 October 2017
Persicaria. Which one?
Thanks … for sharing these images.
I think this is Persicaria sagittata (L.) H.Gross
Please also check the high resolution image of DSC_0451 for the presence of recurved prickles. There seems to be mixture of P. nepalense as well. DSC_457, 459, 448 and 450 are not matching well with P. sagittata. They are probably P. nepalense.
P. sagittata is a polymorphic species. Pl see the quote from Fl. China:
Polygonum sagittatum s.l. is an extremely variable species and known from both Asia and North America. Some authors have pointed out, on the basis of differences in achene surface and leaf margin, that North American populations are separable from Asian ones, and have treated them as two distinct varieties of P. sagittatum, or as two distinct species: P. sagittatum in North America and P. sieboldii in eastern Asia. In Park’s previous taxonomic monograph of P. sect. Echinocaulon(Syst. Bot. 12: 167–179. 1987; and Mem. New York Bot. Gard. 47: 1–82. 1988), P. sagittatum and P. sieboldii are recognized as conspecific mainly based on flavonoid chemistry and also the observation that North American plants are well within the range of variability of eastern Asian ones. However, the recent molecular analyses of North American and eastern Asian populations of P. sagittatum (Park, in prep.) show that these disjunct populations are genetically somewhat divergent from each other. The degree of genetic divergence, however, strongly suggests that they can be recognized either as a single polymorphic species (P. sagittatum s.l.) or two distinct varieties of P. sagittatum, but they can hardly be treated as two distinct species.
I think it is one plant only.
Enclosing link for earlier post for cross reference.
On closer scrutiny of posted images, I also feel they are from the same plant.
I should I take these as Polygonum sagittatum ?
Please also check the high-resolution image of DSC_0451 for the presence of recurved prickles.