Does blue grain work as lawn fertilizer against weeds?

Does blue grain work as lawn fertilizer against weeds?

What is blue grain?

Blaukorn is a complete chemical fertilizer that is no longer entirely undisputed. The product produced in the laboratory is not used in ecological gardens. You have to decide for yourself whether you want to use it, as this depends on the nature of the soil. Ideally, you should take a soil sample in advance.

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Blue grain is commercially available as blue colored granules or in liquid form. This product is a universal fertilizer that can be used for all garden and container plants, including lawns.

The product contains the following ingredients:

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Some manufacturers also add trace elements such as magnesium (Mg) and / or sulfur (S).

Since the composition is not uniform, you should study the information on the packaging carefully.

How does blue grain work?

The blue granules act like a growth booster. It quickly supplies the plants with all the nutrients they need and the effect is clearly visible within a very short time. Evergreen plants in particular, including the lawn, benefit from this fertilization:

  • Nitrogen makes the grass grow stronger and is responsible for the deep green color.
  • Root growth is positively influenced by the phosphorus it contains.
  • Potassium strengthens the lawn and makes the blades of grass more resilient.

As a result, the grass forms dense, green carpets in which weeds can find it difficult to grow.

When is fertilization carried out?

In spring, in particular, it makes sense to provide the lawn with additional nutrients. Due to the high concentration of the grains, you have to pay attention to the exact dosage when applying blue grain. A spreader is therefore recommended.

Warning: less is more, because blue grain can influence the soil properties

If used incorrectly or overdosed, the positive effect of blue grain turns into the opposite:

  • The agent promotes acidification of the substrate, which causes the lawn roots to die.
  • Some weeds such as clover or dandelion really feel at home in the soil that has been fertilized on one side. These can subsequently multiply by leaps and bounds.


If you want to use blue grain, make sure that you do not inadvertently form small piles of granules. If these dissolve, the plant can be massively damaged by the overdose.