Polygonum is from the Greek polys meaning many and gony meaning knee and refers to the many nodes on the stems.
Pink Knotweed because it has pink flowers.
A rather erect, many branched annual plant with oval leaves that are dotted with oil glands.
Stipules - (Ochrea) Membranous, flat topped, hairless, ribbed sheath where petiole joins the stem. Hairless.
Petiole - Short.
Blade - Lance shaped to broadly oval with a pointed tip, 70-200 mm long by 15-60 mm wide, dotted with oil glands, conspicuous veins underneath, usually has central brown blotch, rough due to low lying hairs on the edges and midrib. Base tapered.
Erect or bending upwards, branching, stout, up to 1200 mm tall.
Dense, thick spike, 20-80 mm long. On a stalks(peduncles) with oil glands that is shorter than the spike. 2 or more spikes form a panicle on the ends of stems.
Pink. Less than 4 mm long. On stalks with oil glands.
Bracts - Small flat topped bracts underneath.
Ovary - Style is 2 branched.
Perianth - Less than 4 mm long. Lobes small usually with no or few oil glands (dots).
'Petals' - Small, pink.
Lens shaped nut, edges obtuse, 1.75-2.5 mm long, smooth.
Enclosed in fruit.
Flowers in paniculate, dense, stout spikes.
Leaves lanceolate, glabrous.
Stems erect, stout, glabrous.
Annual. Flowers in summer.
Summer in western NSW.
Flowers in summer in SA.
Seed Biology and Germination:
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:
Africa. new Zealand.
ACT, NSW, NT, QLD, SA, TAS, VIC.
Wet areas, depressions, edges of swamps.
Often on clay soils.
Black box and Lignum.
Rarely grazed by sheep, lightly grazed by cattle.
Weed of watercourses, roadsides, wet areas and disturbed areas.
Suspected of causing dermatitis and death in cattle.
Management and Control:
Cultivate before flowering.
Glyphosate, dicamba and sulfonyl urea herbicides provide good control.