Wireweed (Polygonum spp.)
Stem of Polygonum aviculare
(Photo A. Storrie)
There are two similar species of wireweed (hog weed): Polygonum aviculare, which has branch leaves about half the size of stem leaves, and P. arenastrum in which all leaves are of similar size.
Wireweed is an autumn to early summer germinating annual or biennial. Cotyledons are spear-shaped with a pointed apex, hairless, 7 to 15 mm long and blue-green.
Mature plants have a prostrate habit with branches up to 1.2 m long and a long fibrous taproot. Leaves are blue-green and occur alternately on the stems. Leaves have a short petiole and up to five flowers can be present in the leaf axils. Stems can root at the nodes.
The flowers are small and pinkish white. There is evidence to suggest that considerable variation exists within this species, with fruit dimension and shape the best characters to determine the different taxa.
Wireweed seeds are 1 to 2 mm in length and rusty brown.
Factors that make wireweed a major weed:
- Delayed germination makes wireweed hard to control
- Competes for moisture and nutrients
- Often causes problems with machinery
- Has phytotoxic properties
Further detail about this weed including integrated weed management tactics that could be considered when developing a management plan can be found in the section on problem weeds in the Integrated Weed Management Manual.
Ecology and biology of common weeds are outlined in section 6 of the Integrated Weed Management Manual.