Does magnesium sulfate help against weeds?

Does magnesium sulfate help against weeds?

What is Magnesium Sulphate?

Epsom salt is a powdery or crystalline substance that:

  • odorless
  • colorless
  • and is water soluble.

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Magnesium sulfate is not only used as a fertilizer, but also in medicine and chemistry.

Magnesium is an important plant nutrient

This trace element plays a key role in the formation of leaf green (chlorophyll). If the nutrient is missing, the leaves appear yellowish and the leaf veins appear darker.

Is Epsom salt suitable for weed killing?

Magnesium sulphate is not a weed killer in the strict sense of the word, as unwanted weeds can also benefit from the additional magnesium. However, if the lawn suffers from a lack of nutrients, the sward can become less dense.

Even if you own a garden that is almost free of wild herbs, weed seeds are brought in with the wind. If the growth conditions for grasses are not optimal, weeds such as dandelions and clover will settle. In this case, fertilizing with Epsom salt can indirectly also work well against weeds.

Magnesium sulphate also lowers the pH value of the soil, which can lead to the death of clover in lawns. This effect can be canceled out again by adding lime.

Before you fertilize magnesium sulphate: make a soil sample

Before giving Epsom salts, you should take a soil sample to determine whether there is any magnesium deficiency and / or whether the pH value of the soil is actually too high. The discoloration of the grass as the sole indication of a nutritional deficiency is not meaningful enough.

How is Epsom salt used correctly?

As with fertilizers, the same applies to Epsom salt: A lot doesn't help much. Apply the product as follows:

  • In light and medium-heavy soils, 30 grams of Epsom salt per square meter twice per season.
  • In the case of heavy soils, a single application of 30 grams of Epsom salt per square meter is sufficient.

Crystals and powder are a little easier to dose on large lawns. Proceed as follows when fertilizing:

  • Moisten the lawn with a garden hose or apply it immediately after a rain shower.
  • Scatter Epsom salt.
  • Water thoroughly.


If you have fertilized with liquid manure or urea, the plants are temporarily unable to absorb magnesium and react with the typical yellow color of the leaves. This is another reason why it is important to take a soil sample before giving Epsom salts.