We buy fantastic fresh corn from the farmer's market. If we leave it for a few days, sometimes the cob underneath the kernels has turned black. However, the kernels are still golden and taste fine.

Why does the cob turn black?

  • 2
    I haven't seen this before. A picture would be interesting. How are you storing them?
    – bstpierre
    Commented Sep 5, 2012 at 12:23
  • Good idea, but I've pitched all the examples. :) I've been refrigerating them.
    – dfrankow
    Commented Sep 5, 2012 at 15:00
  • Try this link from Mississippi State University. msucares.com/crops/corn/corn7.html
    – user11672
    Commented Jul 8, 2015 at 2:46
  • @da Thanks for your contribution, but it doesn't answer the question of why the cobs turn black after harvest.
    – Niall C.
    Commented Jul 8, 2015 at 4:20

3 Answers 3


Perhaps this is cob rot, as described here, or one of the many other diseases described there.

This page describes black corn, which can apparently infect the cob.

Many pictures of diseased corn are shown here, perhaps one of them may match your case.

There seem to be a few varieties of fungal infections that would infect an ear of corn, some of which are apparently edible, as shown here.

Overall, it appears there are many varieties of fungal infections that can attack an ear of corn, so its difficult to be sure which one you saw.


Or, since it tasted fine, it is highly likely it was picked just after the growth peaked. Read about it here: https://www.pioneer.com/us/agronomy/kernel-black-layer-formation.html


Not sure this is a useful answer as such, but I have seen this myself. Last week I had corn and the ear (or cob) inside wasn't completely black, but did have the beginnings of blackening at one end, where the tassels would have been, with streaks penetrating the cob itself, yet, as you say, the kernels themselves were fine - looked normal, tasted normal. My assumption is that it's some kind of fungal infection, possibly present in the tassels, and the longer the corn cob is stored, the blacker the ear becomes, as it degrades. Without keeping them for longer to see what happens, I can't say whether they eventually do become completely black.

Having said all that, though, I can't find any real evidence to back up this theory. Smut is the obvious contender, and it certainly can be present on the tassels, but it usually ruins the kernels rather than just the cob itself.

I suppose its possible that the particular variety of corn where you find this to be the case is one where this feature is normal, but again, I can't find a variety listed that mentions this attribute.

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