Grassland reseeds: weed control

Read our information on how to control common weeds in grassland reseeds. You will find information on chickweed, docks, redshank, thistles, nettles, buttercups and ragwort.

As any form of soil cultivation can disturb the weed seed bank, it is important to check new leys regularly for any signs of weed infestation. Weeds are best controlled in new leys when the grass is at the two-to-three leaf stage. However, spot control of docks and chickweed at the seedling stage can be important.

For more information on dealing with weeds, consult a BASIS adviser.

Chickweed is an annual plant that poses a real threat to autumn reseeds. It originates from seed that has lain dormant in the soil. Its rapid growth can quickly shade out seedlings of newly sown species.

Control measures for chickweed:

• Heavy grazing with cattle or sheep can be used to eradicate chickweed, although the newly sown ley must be able to withstand this pressure
• Harrowing may be effective in more established swards – topping is not effective
• Herbicides containing fluroxypyr and florasulam are suitable for grass-only swards
• Herbicides containing tribenuron-methyl are suitable for swards containing clover

Dock seeds can last up to 25 years in soil and germinate rapidly after soil disturbance. Docks have a deep taproot and, once established, are hard to remove. Mature plants can produce up to 60,000 seeds per year, posing a significant long-term challenge.

Control measures for docks:

• Docks must be targeted at the seedling stage to achieve effective control
• The optimum time to spray docks is late spring due to the rapid growth period before flowering
• There is a range of herbicides available for controlling docks, some of which are clover-safe
• Spot spraying may be an effective way of controlling docks early on without checking development of the new sward

Typically found in damp, acidic soils. Rapid germination in spring and early summer will smother grass seedlings.

Control measures for redshank:

• Best treated at the rosette stage
• Effective herbicides include 2,4-D or dicamba

Although less common in new leys, these weeds can still hinder sward productivity.

Thistles can be spread by windblown seed or underground roots.

Control measures for thistles, nettles and buttercups:

• Cut plants early to prevent seeding
• Effective herbicides include 2,4-D, clopyralid, fluroxypyr and triclopyr
• Deep cultivations when reseeding

Ragwort is a biennial plant with leaf development in the first year and flowering in the second. It is highly toxic to stock and humans and is spread by windborne seed.

Control measures for ragwort:

• Graze new leys tightly without poaching or harrow lightly in spring (young ragwort does not tolerate disturbance)
• Avoid cutting
• Effective herbicides include 2,4-D/MCPA
• Pulling light infestations is an option, but always wear gloves and protective clothing