Persicaria strigosa

Pink Knotweed; 

Creeping or suberect herbs; stems angular, the angles beset with small reflexed or recurved barbs or prickles, more so below the nodes. Leaves 3.5-12 x 2-3.5 cm, oblong or linear-oblong, base truncate to hastate, apex acuminate; petiole to 1.4 cm long; ocrea 2-2.5 cm long, long-tubular, truncate, with many excurrent nerves, terminating in erect setae. Flowers 3-4.5 mm across, white, in 6-12 mm long, oblong or subglobose peduncled heads; peduncles 5-15 cm long, panicled, slender, glandular-hispid below the head. Bracts ovate or oblong, strigose and ciliate. Perianth 3-5 mm long, campanulate; tube c. 2 mm long; lobes 5, 2-3 mm long, obovate, obtuse. Stamens 5, alternating with 5, yellow, subulate staminoids; filaments c. 2 mm long; anthers white. Ovary c. 1 mm long, ovoid; style c. 2 mm long, 2-fid; stigma capitate. Nut 1.5-2 mm across, biconvex, reddish-brown to black.
Flowering and fruiting: November-May
Marshy areas
South Asia and China

Persicaria strigosa is found in Bangladesh, Bhutan, China, Indonesia, Malaysia, Myanmar, Nepal, New Guinea, Thailand, Viet Nam and Australia. In India it is found in the Himalaya (Cook 1996) and in Tamil Nadu (Nilgiris and Palnis) (Henry et al. 1987). 

It is found in aquatic or wetland habitats (Cook 1996).

(From  IUCN Red List (LC) on 8.1.14)

A plant from Arunachal Pradesh-4 : Attachments (1). 5 posts by 3 authors. 
I am not quite sure whether these are flowers or buds but they were seen at a number of places in Upper Dibang Valley, Arunachal Pradesh. Some were growing at amidst the profusion of vegetation at shoulder height, and some I found growing just off the ground at Mayodia Pass, altitude 2655m.
I request identification please?
May it be a Polygonum, P. capitatum (the knotweed) ?

It is identified as Persicaria strigosa. Incidentally, I found the Pink Knotweed to be very common in Upper Dibang Valley in Arunachal Pradesh. All along the road and even on stone culverts this weed was growing profusely.