Weed Identification

Low-value Grass Species

Annual Meadow Grass - Poa annua

Annual Meadow-grass is a low-growing grass which is a light green colour. It grows from a central base, to which all the shoots can be traced, and has a creeping rootstock. The blade-like leaves are blunt-tipped and the yellow-green flower head is triangular with branched spikelets that contain the flowers. 

 

 

 

 

Couch Grass (Twitch Grass) - Elymus repens

A very competitive perennial grass weed. Spreads rapidly using sharp rhizomes (underground stems). It can be found growing on most soil types except those with low pH. It prefers heavy land but better able to spread in lighter soils. Germination mainly occurs during the autumn, but seedlings also emerge in spring especially when autumn germination is delayed by cold temperatures or lack of moisture. Reproduction is primarily using rhizomes, so cultivation that spreads the plant segments can worsen the problem.

 

 

 

Crested Dogstail - Cynosurus cristatus

A common, tufted perennial grass weed in grassland and meadows. It tolerates many different soil types but is generally a lowland species. It grows in compacted tufts, and is stiff looking with narrow green leaves. Its dense tillering habit mean it is sometimes added to sheep pasture mixes or amenity mixtures.

 

 

 

 

Sweet Vernal - Anthoxanthum odoratum

Sweet Vernal is a common perennial in grassland and meadows. Flowers early between April and July. Early seed set allows for improved population regeneration from seed, increasing persistence. This species contributes to the sweet smell of cut hay.

 

 

 

 

Yorkshire Fog - Holcus ianatus

A tufted, perennial species abundant in the UK. Seed can germinate over a wide range of soil temperatures and emerge mainly from April to October. Produces tillers that form large spreading clumps in established swards. Plants are relatively deep rooted and there is some evidence to suggest that it may have allelopathic effects on other plants in the sward. Purplish seed head, and soft hairy leaves.

 

 

 

 

Weed Identification    

Buttercups - Ranunculus spp.

Creeping buttercup is a problem in heavily grazed, poached or wet pastures.

• Animals tend not to graze areas infested with buttercup as it has an acrid taste and affects grass yield and reduces hay value.

 

 

 

Common Chickweed - Stellaria media

Common Chickweed is a weed and can persist in rotational grass and establish in long-term pastures where there are gaps in swards due to poaching or slurry injection.

With a prostrate habit and fast growth, chickweed restricts tillering of establishing grass and clover and fills in bare spaces in swards.

Autumn sowings can be a problem as chickweed may overtake the slower establishing grasses and clovers, filling in bare patches.

High moisture content will cause difficulties when trying to wilt for silage and also upset silage fermentation affecting the feed value.

It will also mean a longer drying time for hay-making with loss of quality. Large chickweed populations may cause digestive upset in grazing lambs and calves.

Docks - Rumex spp.

Docks compete with grass for light, nutrients and moisture and reduce grass yields and have less than 65% of the feed value of grass.

Docks are unpalatable and, in general, animals will only eat them if there is nothing else available. Excessive quantities of docks in the diet can cause dietary upsets, especially in young animals.

Presence of docks in silage can affect fermentation, reducing overall quality.

 

 

Fat Hen - Chenopodium album

• A summer annual weed that establishes quickly, particularly if soil is open. Competes with a grass sward for water and nutrients. A prolific seed producer, with seeds that can remain dormant for many years.

 

 

 

 

Nettles - Cirsium spp.

Favouring high-fertility sites, nettles spread through tough roots forming clumps.

Nettles compete with grass for light, water and nutrients and, where nettles are dense, will out-compete the sward.

Grazing stock avoid mature nettles, reducing the productivity of the swards. Nettles in hay or silage may cause rejection by stock.

Best controlled in the spring when they are 30-45cm tall. Frequently cutting nettles often results in more vigorous regrowth.

 

Ragwort - Senecio jacobea

• This weed is potentially deadly to livestock and is listed in the Injurious Weeds Act, which requires occupiers by law to control.

• Under the Ragwort Control Act (2003), a code of practice was developed giving guidance on identification, priorities for control, methods, environmental considerations, and health and safety issues. 

• They have a daisy-like yellow flower, flowering from May to October. Ragwort is a danger to all stock, but particularly horses, cattle, free-range pigs and chickens. Alkaloids cause cirrhosis of the liver and there is no known antidote. 

Ragwort is largely unpalatable; ragwort may be eaten when green, particularly when other grazing is sparse. It is palatable when dead or dying because of the release of sugars, so contamination of hay or silage is very dangerous.

Redshank - Persicaria maculosa

A summer annual weed typically found in acidic soils. Establishes quickly and can smother out grass seedlings. Plant fragments can root at the nodes.

 

 

 

 

Thistles - Cirsium spp.

• There are 150 species of thistles worldwide, with 20 in the UK. Thistles need controlling as they compete with grass for space, light, nutrients and water.

• Thistles are unpalatable to stock and reduce the available grazing, and can increase the incidence of Orf. The 2 most common and damaging are creeping thistle and spear (Scotch) thistle.

Creeping Thistle (Cirsium arvense): A perennial that grows from seed or from root sections in the soil. Once established, the root mass can be greater than the plant above ground, competing with the grass.

Spear Thistle (Cirsium vulgare): A biennial that grows from seed, and in the first year often goes unnoticed, since it produces only a small rosette. In the second year the plant can grow to over a metre in diameter before flowering.