Growing corn, harvesting seed

I have sown two types of corn (maize) this year, they are still in pots waiting to be planted in the garden. They are one variety of sweet corn, and one popcorn maize.
I live in Norway, northern Europe, in a coastal climate, and corn is probably on the border of being possible here. Other places in Norway, with a more inland and warmer climate, grow sweet corn, however, and some places also grow maize for animal feed (silage). I have also grown a few cobs in my climate earlier. It should be possible, if the summer is warm and the seeds are sown early.

I am sorry if I mix up and use the words "maize" or "corn" incorrectly, I don't know the distinction, if any.

I have read that corn can answer rapidly to selection breeding, and would like to harvest seeds to get better adapted plants in the future.
Should my two varieties this year for this reason be grown far apart?

Another, almost unrelated question: I visited Guatemala in 2002, and brought home some maize seeds, red, black and white. These will be flour maize, I believe. I had forgotten about them, and found them again and tried to sprout them this spring, with no success. I have read later that maize seeds can be viable for 3-4-5 years, so my seeds are probably way too old. But can there be any tricks to see if maybe one in 1000 may still germinate? Red maize would be nice to grow. The seeds have been stored dry and not too warm.

We just call it all corn around here.  We raise 7 varieties right now.  We have found that they need to be a little ways apart.  The sweet gene carries over to other corn easily and is detectible by looking at the shriveled up seed.  Our corn has adapted fast to our area with our help.  We have been saving shorter corn stalks, because of the high winds we now get.  Corn is a C4 plant that loves heat.  When it is in the 80's and humid you can almost watch it grow. It will produce some corn in cooler areas from what we have seen.  We have found some teosinte and are trying to get it to cross with some older lines of corn.  We plant them in rows next to each other and try to get a fun cross to study.

There's a few things worth considering when it comes to breeding corn...

You're right that it can adapt quite quickly to an environment, but only if it's starting as a diverse population. A extremely uniform variety will show very little adaptation.

Corn hates being inbred. If you keep growing out seeds of the same small population, after a few generations you'll see a significant reduction in plant health and yield. This is very similar to the effects on humans when a small population inbreeds for some time.
To prevent this, ideally you want to grow a relatively large stand of corn. You will here a minimum of 100, 200, or even 400 depending who you talk to. Personally I think 400 is sufficient.
If you are unable to do this, you can mix seeds you harvested in with ones of the same variety from your seed source, or another seed company, and this should prevent the bottlenecking from occuring.


Corn can pollinate other plants from very far away, much farther than is practical for most people to isolate varieties. The best way to grow two varieties is to plant an early season and a late season corn, this way they will tassle at different times. For people with long growing seasons, they could also stagger their plantings (but I doubt that applies to you).


As for the old seeds, you could try soaking them in a dilute hydrogen peroxide solution. I believe 1% is the normal strength, but you should doublecheck before trying. That said, it would be very difficult to extract those genetics unless you were able to germinate 100 seeds or more, or if you chose to cross it with another variety

I agree with the above...
Corn can cross pollinate up to a mile away with proper conditions so your seed will be a hybrid of the 2.  
As mentioned, grow one type first then wait maybe a month and plant your second type. That should give enough time for the first variety to be pollinated then all pollen spent before second variety pollen becomes viable.   I learned this the hard way many years ago.
I realize you have seedling already started but your seed crop will be crossed.  Better to replant one of the varieties a little later if you want seed.

I'm in Denmark so if you are on the coast in Norway you will have a similar climate, Sweetcorn for fresh eating is perfectly possible.  Though not American varieties they need to much heat and too long a season, but there are plenty of British ones that work fine. But popcorn or drying for seed is a bit hit and miss, in a decent summer I have managed to get about half my popcorn mature enough to dry inside. I have to start the seeds inside in Mid April/early May depending on the year and then put them out a couple of weeks before last frost, they can take some frost when small. Getting the plants going early also means they don't flower at the same time as the fodder maize which would ruin your crop. Our summer temperature averages 20C (68F) in July and August so if that compares well to you then you can probably have at least as much success as I have managed.

To those suggesting staggered planting times, we don't have a long enough season to do that here, corn planted a month later won't even get to sweetcorn eating stage before the season is over.

In that kind of ecosystem, I would focus only on sweet corn. Under the best of conditions, the phenotype for great popcorn is fickle. And it takes a very long season to grow it to maturity. Drying it down in damp, cold, fall conditions is problematic. Sweet corn seed is viable about a week before the earliest fresh eating stage.

If the Guatemalan corns are tropical, they are unlikely to start flowering until the fall frosts are already upon them.

Thank you for your answer. We will see how it goes with the various types.
The Guatemalan corn is from the highlands, I believe around 1000 meters above sea level.
They did grow avocado there, but not the tropical stuff from the coast (like for example citrus, mango and pineapple), if I remember correctly.