Yes. Unlike some vegetables, corn doesn’t continue to ripen once it’s off the stalk, so it’s picked ripe. Some ears will have a few more developed kernels than others at their tips, which is obvious when you peel back the husks. That’s what people are looking for. That, and any worms or bad spots.
Here’s what the grower is looking for when he or she is harvesting corn. The ends of the silk begin to dry and turn brown. The kernels are plump all the way up the ear to the tips. When pierced by a fingernail, one of the kernels will exude a milky liquid. The harvester will have pulled back the husks on a few ears to check for this, so the purchaser doesn’t need to.
First and foremost, try to buy as close to the field as possible. Although with the newer supersweet varieties it’s no longer true that you should allow no more than an hour from the field to the kitchen to cook up corn, it’s still true that the fresher it is, the better. So in season where you live, avoid buying corn at the supermarket. Often, a farm stand will sell day-old corn for less than corn picked earlier that day. That’s one way to tell how fresh it is.
Failing that, here’s what the purchaser should look for. The stems and husks of fresh corn should be fresh and light green rather than straw-colored, not the least bit dried out. Brown stems are a dead giveaway that the corn is old. Are the kernels nice and fat all the way up the ear? You can tell that by feeling the tip of the ear through the husk; there’s no need to rip back the husks halfway down the ear roughly (although you can gently peel it back just a little for a peek; if the kernels look too skimpy to you, simply replace the husk and put the ear back in the pile.) As for the worm? I seldom find them; and when I do, hope it’s a sign the corn hasn’t been sprayed too heavily.
One of the farm stands here offers a nice convenience. Next to the corn display are large trash barrels for the husks and silks, so customers can clean the corn before they take it home. I don’t know whether they compost the contents of those bins, but I hope so. The only caveat to cleaning corn before you buy it is that you should do this only if you’re planning to cook it soon. The husk and silk are nature’s own little wrapper which will keep the corn fresh until you’re ready to cook it. That and rapid refrigeration will ensure your corn stays as sweet and tasty as possible.