Corn in the North

As a kid being driven on a family trip through the Thunder Bay area, I was surprised by the fields of corn. I knew enough by then to distinguish field corn from “people” corn, but I was surprised to see corn growing at all on the eaves of the boreal forest.

Corn patch, Aug. 28, 2007

Well, whether it’s cow corn or sweet corn, when it comes to growing it, the key is to choose varieties that require a fairly short growing season. There are varieties that grow reliably here – although you will occasionally be caught short by frost. Ripening ears of corn will not tolerate frost, even if the leaves will. This is what happened to mine during my first “experimental” gardening season in 2007, when we had our first hard-ish frost on the morning of September 12. My corn had a few days to go, but that was that.

Still, I noticed at the farmers market the next weekend that the Slate River Valley corn producers, like Belluz Farms, were still going great guns. Their land is a little lower in elevation than mine, and a little further south. Increments make a difference!

The variety I grew was Sugar Buns, an early “sugary-enhanced” (se) yellow type from Johnny’s Seeds. Examining the ears, I saw that they were good size with complete tip fill. If you try corn in a northern climate, find a good variety that ripens in 70 days or less.

Another consideration is germination in the spring. You want to take advantage of as much of the growing season as you can. How early can you plant? Answer: as soon as the soil is warm anough that the seeds won’t rot. And here’s where things can get technical. Back in the “old days”, sweet corn was sweeter than “cow corn” simply because it was picked younger. Then breeders began selecting to create sweeter varieties. These are the “normal sugary” (su) varieties, and these plants are fairly robust, with seeds that will germinate in cool-ish (but not cold!) soil.

The next development in sweet corn occured when breeders began selecting specifically for a naturally occurring gene that promoted even more sweetness and tenderness in the kernals. The resulting varieties are called “sugary enhanced” (se) and (se+). Their seeds, which contain less starch, are somewhat more sensitive to cool, wet conditions when they are planted.

[A note here – we’re not talking about genetically modified or GMO varieties on this page, but rather varieties developed with normal breeding methods to promote naturally occurring corn genes]

As time went on, breeders discovered one more naturally occurring gene in corn that they could breed for. This one promoted extreme sweetness, and the resulting varieties are called “Super Sweet” (sh2). Take note, the “sh” stands for shrunken. These kernals are so high in sugar and low in starch and protein that, when dry, they look like little chips. They have so little substance that they absolutely love to rot in cool temperatures. They can’t be planted early. Also, the ears of these varieties must be fully mature before picking – undermature ears have no flavour or sweetness. On the plus side, when picked at the right time the ears are very sweet, and hold their sweetness well in storage.

The Johnny’s Seeds catalogue has a good explanation of all this, and of how to isolate the different sweet corn types if you are growing more than one of them. But back to the relevance of all this for northern gardeners – the older, less sugary types germinate better in cool ground. Beginning gardeners should definitely go for (su) or (se) types. I don’t know what Belluz Farms grows, but they may do this, too. And, in my personal opinion, the older, yellow varieties is where the flavour is. Picked at their peak, they are very sweet, with real “corn” flavour!

If you want to get fancy or try a variety that needs more than 70 days, you can try germinating kernals indoors between wet paper towels, and carefully planting the sprouted seeds. Another aid you can use, if you are not growing organically, is seed treated with mild fungicide (that “pink stuff”). This will buy you a few days on the spring end of the season. And finally, several seed catalogues are now offering seed with a coating called Natural II, which is said to protect the seed from cold and wet conditions and provide a few nutrients to get it going. The coating is compliant with most organic guidelines.

My final corn word, for now, is about pests. In Southern Ontario our corn was plagued with corn borers. I found them very yucky, and of course they ruined many ears. Discouraging them in large plots seemed to call for very nasty pesticides, and I was ready to give up. There are natural methods for killing pests on corn, but before I had a chance to try them I moved here to the North. When I grew my plot here in 2007, no pests visited it. I’m sure the isolation and newness of the plot was a big part of that, but it could also be that there are somewhat less pests here. When I try corn again, I’ll give you an update. Also, make sure to see Kevin Belluz’s (goodgrowing) comment below.

Earlier Comments:

Pete Summerfield, April 14, 2009
What! No Corn Borers? Here on the Great American Mudflats we suffer three or four generations of ‘em every year. And earworms and rootworms to boot!