New Sown Leys Weed Control

young grass ley

Reseeding is an important part of grassland management, and is essential for maintaining productive grassland.

New sown leys leaflet

Average costs for a reseed are between £400-£700 per hectare, so it is important to do it correctly. The current best practice advice can be found in the  AHDB Grassland Reseeding Guide.

When to reseed - autumn or spring?

There are two key timings to look at establishing grass in the UK - autumn (August to October) and spring (March to May), with autumn being the most common time to reseed. Successful establishment can be achieved at either timing, and there are advantages and disadvantages to each time of year.





Minimal impact on grazing as land not taken out of production at peak growth times

Seedbed has time to settle over winter, allowing good structure to form

Good weed control if done early and you catch weeds when they are still actively growing


Higher probability of good conditions for establishment

As grass is actively growing it can better out-compete weeds

No heading in first season



Significant weed competition from late reseeds

Narrower window for good establishment


Losing peak growth by taking field out of production at this time

Soil does not have time to settle before carrying stock.


More detailed information on autumn reseeds can be found in the AHDB Now is the time for autumn reseeds article.

Weed Control

The key to successful establishment of a new ley is of course ensuring a good seedbed and adequate pH and nutrient availability, and choosing a suitable variety, but once the grass is sown, keeping weeds out becomes equally important. Early competition from vigorous weeds such as chickweed and mayweed can rapidly reduce the growth of grass and leave new leys ‘gappy’ and unproductive. An uneven grass ley can take a considerable time to become fully productive.

Tackling grassland weeds early, at establishment of a new grass ley, will help improve sward palatability, productivity and reduce costs. As any form of soil cultivation will disturb the weed seedbank and encourage germination of weed seeds, it is important to check new leys regularly for weed infestations.

The most common weed issues after reseeding are chickweed, docks and thistles. However, a wide range of perennial and annual weeds will take advantage of warm temperatures and a moist seedbed to germinate, including mayweed, shepherds purse, annual meadow grass, red shank and pansy. Weed seedlings are more susceptible to herbicides than mature plants and are cheaper and easier to control at this stage.

Many grassland herbicide products dictate that grass should be ’established’, i.e. over a year old at the time of treatment. However, Corteva Agriscience has two selective herbicides for use in new sown leys - Leystar™ and Envy™ for application from as early as when three grass leaves have appeared.

Leystar™ can be applied to new sown leys at 1.0 L/ha from 1st February to 31st August, and so is suitable for use on spring established new sown leys. Envy™ can be applied to new sown leys at 1.5 L/ha from 1st February to 30th November and so can be used on both autumn and spring established new sown leys.

Leystar™ and Envy™ are not safe to clover, but clover can be stitched in 3 months after application.


Products for use in new sown leys