Polygonum is from the Greek polys meaning many and gony meaning knee and refers to the many nodes on the stems.
Pale Knotweed.
Other names:
Pink Knotweed because it has pink flowers.
Summary:
A rather erect, many branched annual plant with oval leaves that are dotted with oil glands.
Description:
Cotyledons:
Two.
Leaves:
Alternate.
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.
Stems:
Erect or bending upwards, branching, stout, up to 1200 mm tall.
Flower head:
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.
Flowers:
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.
Stamens -
Anthers -
Fruit:
Lens shaped nut, edges obtuse, 1.75-2.5 mm long, smooth.
Seeds:
Enclosed in fruit.
Roots:
Taproot.
Key Characters:
Flowers in paniculate, dense, stout spikes.
Leaves lanceolate, glabrous.
Stipules glabrous.
Stems erect, stout, glabrous.
Nut biconvex.
Biology:
Life cycle:
Annual. Flowers in summer.
Physiology:
Reproduction:
By seed.
Flowering times:
Summer in western NSW.
Flowers in summer in SA.
Seed Biology and Germination:
Vegetative Propagules:
None.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:
Africa. new Zealand.
Distribution:
ACT, NSW, NT, QLD, SA, TAS, VIC.
Habitats:
Wet areas, depressions, edges of swamps.
Climate:
Temperate.
Soil:
Often on clay soils.
Plant Associations:
Black box and Lignum.
Significance:
Beneficial:
Rarely grazed by sheep, lightly grazed by cattle.
Detrimental:
Weed of watercourses, roadsides, wet areas and disturbed areas.
Toxicity:
Suspected of causing dermatitis and death in cattle.
Legislation:
None.
Management and Control:
Thresholds:
Eradication strategies:
Cultivate before flowering.
Glyphosate, dicamba and sulfonyl urea herbicides provide good control.