Fertilising Lawns in Winter

Your lawn needs a mix of nutrients to help it function at optimum capacity. Potassium and other nutrients create a healthier lawn that is more resilient to drought, temperature change and disease.

At certain times of the year, some nutrients can be more important than others. During autumn when temperatures are starting to decrease, there is one nutrient in particular that needs to be readily available for your grass to absorb to help prepare it for winter. This nutrient is potassium. Most people know about nitrogen and its ability to provide quick green up and leaf growth, but now is the time to boost the health of the entire plant, and this is where potassium comes in.

What is potassium?

Potassium is a chemical element (K) which was initially derived from potash. Without it, your lawn would struggle to grow, be lacking in strength and suffer yellowing of the leaf.

What does potassium do for your grass?

Potassium functions within the cell of the grass and provides strength to the whole plant. It helps the internal processes including photosynthesis, respiration and protein production creating thicker cell walls.

If you have been fertilising your lawn with a balanced slow release granular fertiliser throughout the year and have done so in autumn, a specific winter fertiliser will generally not be required and the potassium levels in your soil should be sufficient. Cool season grasses continue to grow strongly throughout winter, so there can be times where a ‘winterizer’ fertiliser with a higher potassium component or where an application with potash might be required, particularly in the more southern Australian states.


The key ingredient you will find in increased amounts in most winter fertilisers is Iron. Iron helps to strengthen your grass and improve leaf colour. Provided you have fertilised in Autumn and have your lawn well prepared for winter, you will be looking at providing an additional treatment around July in most states. You can apply Iron Chelate which will help to get better iron uptake for better results without the Nitrogen promoting unnecessary growth.

If you haven’t fertilised this season, now is a great time to do so. A good quality slow release fertiliser will contain all the nutrients your lawn needs, including potassium and iron, and will last for up to 12 weeks.

Source: https://lawnsolutionsaustralia.com.au/lawn-care/winterizing-lawn-potassium/