How do I know when to harvest my popcorn?

Question

I have some heritage "Strawberry" popcorn plants in the garden, and I've realised I don't know when to harvest them. Though it might be possible to eat it while still fresh and juicy, I intend to pop it into popcorn so the kernels presumably need to be left longer than sweetcorn to mature. Is there some way I can tell when it's ready to harvest?

Edit - here's the end result (well, not quite, as I haven't popped it), to be left in the kitchen like this to dry for a couple of weeks:

Answer 1

Iowa State University Extension says:

Allow the kernels to dry in the field as long as possible. When harvested, the kernels should be hard and the husks completely dry.

I've never grown popcorn, but it looks like a hard freeze can damage the kernels. So let it dry in the field as long as you can, and harvest prior to any hard freezes. I'd probably also want to pick it if I knew there was a lot of wet weather coming and the corn wouldn't dry any more outside.

Answer 2

Further to @bstpierre's answer: harvest as dry as you can, then bring indoor and shuck to seed, then spread that out and dry for some additional time. But don't apply heat to dry; just air-dry at room temperature. It is the residual moisture that causes it to pop -- too wet or too dry, and it won't pop.

You can pop this in a microwave right on the cob!