From scratch in this case means not buying the expensive sweet potato plants (slips) from the garden center. They easily sell for £3 -£4 per plant. And you need a lot to get a good crop of sweet potatoes. Last year Matt and I tried growing 2 plants. We got maybe 6 sweet potatoes from those two plants that varied in size. This year we decided we wanted more but didn’t want to spend the money buying plants. So we googled it. The whole process took about 10 months, from potato to potato!