I haven't grown Sweet potatoes (kumera) before, and I'd just about given up, as each time I checked under the lush vine there were only scrawny little roots.
When I was watering them this morning, after not doing any checking for almost a month, I saw that the soil was raised in heaps. I dug into the soil and unearthed this (my size 7 boot is for comparison)
which was a huge surprise as I thought the whole project had failed. On quick investigation I discovered there are quite a few other tubers around this size available.
Maybe it just needed a cool change to the weather to encourage the vine to store more energy in it's roots, making them larger!
I'll harvest as required as I don't need the garden space they are growing in. Considering the current price of these at the shops I think it's worth it to have these home grown.