Polygonum aviculare or Common Knotweed is a plant related to buckwheat and dock. It is also called birdweed, pigweed, wireweed, common knotgrass, matgrass, doorweed, pinkweed, birdgrass, stonegrass, lowgrass and prostrate knotweed.
It is an annual found in fields and wasteland and, occasionally, in roadsides, gardens and turf grass from June to October.
The English botanist, herbalist, physician and astrologer, Nicholas Culpeper, recommend knotweed to cure the spitting of blood. Modern herbalists use it to treat dysentery, excessive menstrual flow, lung disorders, bronchitis and jaundice, and gall and kidney stones. Not all of these uses are supported by scientific evidence!
Knotweed has a prostrate form of growth, especially in close mown turf. Stems are very long and nodal with leaves forming alternately along the stem.
The prostrate stems merely trail across the ground, clamber over, or lean upon other plants, rocks, fences, or whatever happens to be in the way.
Knotweed stems can grow up to one metre in length. They often sprawl over the ground surface but may have an erect habit in other situations.
Height can vary between 10cm and 60 cm. The rootsa are fibrous and shallow.
The flowers are small and white, with petals 2.5-3.5mm long, greenish with pink or white margins. In contrast to other Polygonums, there is little or no honey or scent, so the flowers are very rarely visited by insects and pollinate themselves by the incurving of the stamens. Flowering period May-October.
The leaves are alternate, oval, apex pointed and hairless, 5-30mm long 1-8mm wide
The plant reproduces by seed.
Habitat: Found mainly on arable land, however, once established, can be a problem in turf grass areas.
Miscellaneous info: The plant has astringent properties, and is used as a herbal remedy for treating diarrhoea, bleeding piles and all haemorrhages.
Cultural Control: Knotweed can be mechanically or physically removed. Care should be taken to ensure that all roots are thoroughly removed. Close mowing reduces seed head formation. Maintaining a dense sward will deter or prevent plantains from establishing. Regular aeration of the soil will help establish better grass growth and reduce the likelihood of compacted soils.
Chemical Control: Apply selective broadleaf herbicides when plant growth is active. There are a number of products available for controlling broad leaf weeds in established turf.
These chemicals are best used when the weeds are actively growing, usually between April-October.
Re-Act - Scotts
Active Ingredients: 256.25g/l (22.6% w/w) MCPA, 237.5g/l (20.9% w/w) mecoprop-P and 31.25g/l (2.8% w/w) dicamba as the dimethylamine salt formulated as a soluble concentrate.
Relay Turf - Headland
Active Ingredients: contains 200g/l Mecoprop-P, 200g/l MCPA and 25g/l dicamba.
Estermone - Vitax
Active Ingredients: Contains: 200g/l 2,4-D as the iso-octyl ester and 35g/l dicamba.
Spearhead - Bayer
Active Ingredients: 20g/l (1.72% w/w) clopyralid, 15.9g/l (1.45% w/w) diflufenican and 300g/l (25.9% w/w) MCPA.
These herbicides are usually applied as a liquid using watering cans, knapsack sprayers and vehicle mounted sprayers.
Ensure you follow manufacturer's directions, health & safety and product data sheets, and comply with COSHH regulations when using these chemicals.