The message
from "Gilly" contains these words:

I'm growing Nadine potatoes in those large black plastic potato bags (sort
of like heavy-duty, short bin liners).

This is the first time I've ever grown spuds. The soil is now up to the top
of the bags, but there's loads of tall stems and leaves above the soil.
They're just beginning to show flower buds.

I tried that and the best I can say is that it's better than doing nothing.

Do I simply leave them and dig around when I want the potatoes, or is there
a correct time to harvest?

That depends whether you want new potatoes or not-quite-so-new ones. I'd
remove the flowers to increase the crop of spuds, and then you can
choose: dig new potatoes when the foliage is mature, not-so-new ones
just before the foliage begins to die off, or slightly older ones when
the haulm has died.

If you want to keep the spuds, you should not dig them until a fortnight
or three weeks after the haulm has died off. (Or been killed off.
Commercially, strong sulphuric acid is used, but I'm not recommending
that.)

--
Rusty
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