Water knotweed (Persicaria amphibia) profile

Written by Maggie

Mar 04 2021

Water knotweed (Persicaria amphibia) profile

Water knotweed (Latin name: Polygonum amphibium L.) is a perennial herb of the genus Polygonum in the Polygonaceae family, having transverse rhizomes. Racemes are spicate, terminal or axillary. Achene is suborbicular, biconvex, black, lustrous, enclosed in persistent perianth. Water knotweed is widely distributed in Asia, Europe and North America.

Water knotweed is born in shallow Water at the edge of lakes, ditches and wetlands near fields, with an altitude of 50-3700 meters. water knotweed can be used for dysentery and whitlow boils.In addition, Water knotweed has large leaves, large flower spikes and attractive pink inflorescence, which makes it a good ornamental plant in the Water landscape.

Water knotweed picture

Water knotweed

Morphological characteristics of water knotweed


Herbs of perennial Water knotweed, rhizomes transverse. In water: Stems are floating, glabrous, nodal adventitious roots.


Leaves of Water knotweed are oblong or elliptic, floating on Water, 5 -- 12 cm long, 2.5 -- 4 cm wide, tip obtuse or slightly acute, base subcordatate, both surfaces glabrous, entire, glabrous; Petiole is 0.5-3 cm long, emanating from near middle of opiculus sheath; Stipules of Water knotweed are cylindric, membranous, 1-1.5 cm long, apex truncate, glabrous; Terland born: Stems are erect, unbranched or branched from base, 40-60 cm tall, leaves lanceolate or oblong-lanceolate, 6-14 cm long and 1.5-2 cm wide, apical acute, base subrounded, both surfaces short hirsute, entire, ciliate; Petiole is 3-5 mm, emanating from middle opiculus sheath; Stipules of Water knotweed are cylindric, membranous, 1.5-2 cm long. Sparsely growing hirsute, apex truncate, with short ciliate.


Water knotweed racemes spicate, terminal or axillary, 2 -- 4 cm long, bracts broadly funnel-shaped; Perianth is 5-lobed, reddish or white, oblong, 3-4 mm long;Stamens usually 5, shorter than perianth; Style 2, longer than perianth, stigma capitate.


Achenes of Water knotweed are suborbicular, biconvex, 2.5 -- 3 mm in diam., black, glossy, enclosed in persistent perianth.

The flowering period of Water knotweed is in summer, and the fruiting period is in autumn.

Ecological habits of water knotweed

Water knotweed grows in shallow Water, ditches and field wetlands at the edge of lakes, 50-3700 meters above sea level.

Water knotweed

How to control water knotweed

Combination of agronomic measures and chemical weeding should be adopted for control.

(1) The main agronomic measures are as follows: firstly, the rice production environment should be established with smooth land, smooth ditch, good water retention and free irrigation; Two is the combination of seed treatment to remove weed seeds, and combined with ploughing, land preparation, eliminate weed seeds on the soil surface; The third is to implement regular crop rotation, reduce the occurrence of weeds;Four is to improve the quality of sowing, sowing seedlings, seedlings to press grass.

(2) Chemical weeding, most places use one-time closure, is in 1-3 days after sowing (accelerating germination), with 40% "direct green" wettable powder 60 grams, mixed with water 40-50 kilograms, uniform spray, pesticide application field plate to keep wet.Irrigation and field management were resumed after 3 days.After removal, if there is still a certain amount of weeds in the later stage, targeted method can be adopted for supplementary removal.

The distribution area of water knotweed

Water knotweed is produced in Northeast, North, Northwest, East, Central and Southwest China.

Water knotweed is distributed in Asia, Europe and North America.

Water Knotweed garden use

Water knotweed is an ornamental plant with large leaves, large flower spikes and lovely pink inflorescence.

Water knotweed flower language

Water knotweed: usually refers to dependence, aspiration and yearning.

Water knotweed