When the tassels have dried and turned brown, or even black, some say
the corn is ripe. If you can feel that the kernels at the free end of
the ear are developed, that is a good clue. My wife actually peels back
a bit of the husk and looks at the kernels to make her final decision.

Most sweet corn is good only for about a week, after that it becomes
tough. Depending on variety, the flavor can degrade (the sugar converts
to starch and the sweetness is gone) within hours of picking. My wife
checks that the corn is ripe, then puts on the water to boil. When the
water is just about to boil, we pick the corn, shuck it, and toss it
into the boiling water. You won't have too much; its easy to eat four
or five ears at a sitting.

Matthew Reed wrote:
This weekend my corn tassels opened and started to drop pollen. How long
does it take for the corn to mature? And how long can it remain on the
plant? I have about 30 plants, and will probably have about 50-60 ears
ripen. I have 4 blocks total, each timed to ripen about 1-2 weeks apart.
Hmm...200 ears of corn in one month. Did I over do it? :-P