You need to understand your enemy and exploit its weaknesses, according to Sarah Cooke of ADAS in the UK.

She was speaking at the Teagasc grass weeds conference last week in Co Kildare and has seen the development of the blackgrass problem the UK.

She warned how the problem can go from having one plant in one metre squared to 6 million seeds per hectare.

“Your population can go from a very small population to a massive population within one, two, three years if you don’t do anything about it,” Sarah commented.

She explained that 500 heads/m2 before harvest if collected is about 1.2 pint glasses of seed.

“That’s about four tonne-bags going back into your fields per hectare. That’s more than you would ever sow of winter wheat,” Sarah noted.


In order to get the weed under control, she said you need to understand it and exploit its weaknesses, adding that you can get rid of the weed from the seedbed over five years with the right interventions.

Most of these interventions do not come from a chemical can.

Getting the crop in in good conditions is important. Having a competitive crop, without bare patches is really important. Blackgrass thrives in wet conditions.

“Give them the space and they’ll take a mile,” Sarah commented.

If you take an autumn like we are currently having in 2023, there is a lot of bare patches in crops, so farmers with a grass weed problem will need to keep an eye on those bare patches and control the weeds later on in the season.

We have all heard the cultural control methods numerous times. Delay drilling, as 80% of blackgrass weeds germinate in the autumn. If you can plant a spring crop, it is all the better.

Strengths of blackgrass

  • Easy to contaminate crops.
  • High seed production.
  • Growth in wet conditions.
  • Spring emergence.
  • Weaknesses of blackgrass

  • 80% comes up in autumn.
  • 70% seed decline over the year.
  • Cannot germinate from depth.
  • Resetting the system

    Sarah said that ploughing for one year in a reduced tillage scenario where blackgrass is a problem can reset the system.

    Sarah explained that inverting the soil puts the seed deep into the ground, but noted that deep tilling is one of the worst things that you can do, as it churns up the soil through the depth of the cultivation.