Potatoes can be ‘earthed up’ as they grow; this involves bringing soil up around the shoots to make a ridge. It helps control weeds, prevents the tubers turning green and gives some protection against tuber blight. Do it first when plants are around 15cm tall, leaving about 5cm of foliage showing. Earth up again just before the foliage meets across the rows. Plants can be mulched with a layer of hay, straw, leaf-mould or grass clippings. This will have the added benefit of conserving soil water. On a closer spacing, earthing up will not be possible, but the shade the plants provide each other will have the same effect. https://www.gardenorganic.org.uk/factsheets/growing-potatoes