Mulching with organic materials can greatly benefit your Common blackberry plants. Organic mulch, such as straw, wood chips, or shredded leaves, helps retain soil moisture, suppress weeds, and add organic matter as it decomposes. Apply a 5-8 cm (2-3 inch) layer around the base of your plants, being careful not to pile it against the canes, which can cause rot. Regular mulching will maintain an optimal growing environment and protect the soil.