Sweet potatoes

I'm afraid I don't have any advice but you have got me interested in growing sweet pots myself because I love eating them.

Be interested to know. traditionally they have grown in warmer climes. In NZ they were grown in N island but not the cooler south - known as kumara. (this is handy info if you want to look up recipies on internet as all NZ and Oz recipies will be for kumara)
Maybe you could prod about under the greenhouse soil to find out if there is anything swelling underground?

Jess , my daugher had a lovely crop in South Island (she does live at the 'top end' close to Nelson). She introduced me to them and now I buy them whenever I see them in the supermarkets here. They are delicious, and make wonderful soup.

I love sweet potatoes and now will try and grow them here too. They are very happy as an accompaniment to lamb, there's nothing like roast sweet potato (you don't have to peel them) split and served with a dollop of sour cream or creme fraiche, and they're fab in a curry. Enjoy.

Yes Nelson has a microclimate - and of course all that lovely wine is grown not so far away. I meant by the Maoris - only the N island had kumara. Can't remember where I picked that up.

Have decided not to pry under the soil but just be patient and wait until the leaves wither naturally. What's the betting there's nothing to harvest when eventually I look?

Last year, DH decided to plant two sweet potato plants in my polytunnel, where they promptly took over the entire length (about 40ft) and I was sure they were walking through the garden at night! Naturally we named them the Triffids, I watered and fed them throughout the summer. Eventually I dug them up - sadly, only a few very small tubers , the plants had obviously put all their energy into the beautiful leafy "vines". Certainly won't try again, but hope you have better luck!