How To Prevent Weeds Growing Through Bark Mulch

How To Prevent Weeds Growing Through Bark Mulch

Expectations of the chopped bark are high, but are sometimes you can be disappointed. Why weeds sprout despite the mulch layer – and what you can do about it.

Pay attention to quality when buying bark mulch


Bark mulch is the shredded bark of various deciduous and coniferous trees. However, the term “bark mulch” is not precisely defined by law. This means that bark mulch does not necessarily have to consist of bark. It can also be composed entirely of foreign materials, as long as they are of plant origin. It can be a mixture of plant residues, shredded branches and chips.

Often, especially cheap bark mulch is not sifted. Therefore, it contains both very large pieces, and fine, sandy material. In addition, poor storage can lead to rot and damage the growing plants.


The following reasons may be responsible for weeds sprouting despite bark mulch:

  • The mulch layer was applied without first removing existing weeds. Once you have removed the weeds, you can apply a special water-permeable fleece from a specialty store or a thick layer of newspaper to the soil. This will prevent weed growth.
  • Before applying the bark mulch, the soil was not sufficiently loosened. As a result, the soil under the layer of chaff is compacted. Precipitation can only seep away poorly and the mulch is permanently moist. These are optimal growth conditions for weed seeds.
  • The mulch layer is not thick enough. Seeds dispersed over the wind thus have the opportunity to root in the soil underneath. The applied layer should therefore be at least five centimeters high – depending on the grain size.
  • The bark mulch was mixed with soil when creating or later planting plants. As a result, it has lost its suppressive effect. If planting is to take place after the mulch has been applied, completely clear the area of the bark pieces beforehand. Before reapplying, sift the mulch carefully so that no soil is mixed in.
  • The chipped layer has been there for more than three years and has partially decomposed. Or it has been mulched on a slope and not secured against washing away. As a result, parts of the soil are no longer covered and provide the best conditions for flying seeds to take root.

What else mulch does


In addition to suppressing weed growth, bark mulch has other positive properties. It keeps the soil moist longer and provides good cold and frost protection for sensitive roots. The layer protects the soil from heavy rain and its consequences.

In addition, the mulch layer decomposes over time – humus is formed. This in turn has a positive effect on soil life, releasing nutrients in the long term.

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