Control of liverwort (Marchantia polymorpha L.) growth in nursery plants with mulches of Sphagnum moss and blackcurrant stem pieces

Liverwort (Marchantia polymorpha L.) is a problematic weed on container surfaces in nurseries, because it hampers water and nutrient access to growing plants. No chemical herbicide against it is available in the EU. Mulches are the most common non-chemical weed control method. Mulches of Sphagnum moss and 1-cm blackcurrant stem pieces were used. Mulches’ effect on liverwort control continued for two years on highbush blueberry and blackcurrant, and one year on rhododendron. The blackcurrant stem pieces trial continued for one year. Blueberry and rhododendron demand acidic growing media, creating an acute need for liverwort control. Sieved moss was used in two different layers on top of a pot. The prevention rate of liverwort growth in blueberry in July–August was 95–99%, and in October 78–90%, depending on weather conditions; in rhododendron and blackcurrant, it was 90–95%.The control effect was diminished in more decomposed moss. No significant difference between thickness and coarseness of moss mulch layers was observed. Blackcurrant stem pieces controlled liverwort growth by almost 100%.