Papua New Guinea sweetpotato seedlings, these pictures should provide an answer.
Sweetpotato Knowledge Portal to show me where I've been going wrong.
So the next step (late though it is) is to stick them in the ground and see how they cope with the Cornish summer; not for the first time, this seems to consist of alternating rain, gales and brief salvoes of scorching sunshine.
What now, kaukau? The answer's easy - I'll plant you out, tout de suite. But planting space at Oca Acres is running a bit low at present. Where now, kaukau: that's the real question.