Graham explains the benefits of seaweed

Any time from spring to autumn is suitable for taking daphne cuttings. Take a cutting of approximately 10cm length, including a node (a swollen section of stem where leaves, stems, roots originate). Dip this into rooting hormone gel or powder and place into propagation mix deep enough so that it stands by itself. A plastic cover over the pot will help retain humidity. Place in a protected position out of direct sunlight. Keep moist and expect roots in a couple of months.

You should be ready to harvest your first batch in February. Simply use your hands to feel through the light mix you have used and pull up as many potatoes as you need for dinner. You can keep on harvesting as you need the potatoes until you run out, or until the start of next winter.