Recent survey figures have confirmed that the area of winter oilseed rape (OSR) increased significantly (44%) in 2022.

Many growers are now seeing the benefits of including it in the farm crop rotation, as it is an ideal break from cereal rotations and is a good entry for first wheats.

Other benefits include spreading the workload, soil structure improvement, and it can be used to control difficult grass weeds.

Again in 2022, many growers were able to reduce the amount of nitrogen (N) required to grow the crop. This was a significant saving this year given the costs of fertilisers. Early drilling is essential for growing oilseed rape.

When to sow oilseed rape

August-drilled crops generally perform better than September-drilled ones and it may be easier to prevent pigeon grazing of large canopies, which in turn will reduce the amount of N needed.

According to Teagasc, the sowing of OSR crops should take place during August and into early September, ideally before September 10.

Seedbeds should be of a high quality – fine and firm. This factor is as important as is the sowing date.


The Department of Agriculture, Food and the Marine (DAFM) Recommended Winter Oilseed Rape (WOSR) list is the best source of information on the main varieties.

Conventional varieties or hybrids can be sown in August. However, come September, only hybrids should be sown out.

Growers should look for varieties with good traits. These include light leaf spot resistance and pod shatter resistance.

A planting rate of 60-80 seeds/m2 is recommended to establish 30-50 plants/m2 in the spring.

Varietal differences in vigour and thousand seed weight, along with seedbed condition and sowing date must be accounted for. Poor seedbed and late sowing will need higher (10%) seeding rates.

Where weed control is concerned, field history is very important. Volunteer cereals, cleavers and grass weeds are the main competitive weeds, and do most of their damage early in the crop’s growth.

Apply pre-emergence or early post-emergence treatments.

Clearfield varieties offer an opportunity to grow oilseed rape in fields where brassica weeds such as charlock, hedge mustard, etc., are a problem.

The herbicide Cleranda is specially developed for clearfield varieties and not only does it control charlock, it also controls groundsel, fumitory, poppy and speedwells. However, Cleranda can only be used on clearfield hybrid varieties.