Sweet Corn

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

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!

What I’m coming to is that the compromise that your short season forces on you is less than the one that pests force on us. And if your neighbors aren’t growing field corn you dont have the problem of cross pollination ruining the flavor of your crop.

There are two ways of dealing with corn pests: chemicals, which repel customers, or GMO’s (InsectProtected corn), likewise a no-no with consumers.

The solutions to short season, like transplanting, mulching and tunnels are all a lesser concern from an ecological standpoint than Furadan and Bt Corn.

But no matter how or where you grow sweet corn your customers have to pay for the space it takes up and the work it represents. Hell, if a candy bar fetches a buck, why not 50 cents an ear for gourmet quality sweet corn? No sense in giving it away.

Good luck!



Wendy (author), April 14, 2009
You’re right, Pete – we’re really quite lucky when it comes to pests.

Local sweet corn does go for 50 cents an ear here, and yessirree – it’s worth every penny!



El Olo, May 12, 2009
When does the first crop of “people” sweet corn arrive?

Hungry for a retour


Wendy (author), May 12, 2009
Hi El Olo! I remember you! (for everybody out there in internet-land, this fellow is a friend of ours from Sweden, and visited us last summer).

Well, in Southern Ontario and down into the USA, you might see sweet corn as early as the end of July, but in Thunder Bay Region we consider ourselves lucky to have some by September 1. You didn’t see any in my garden during your visit last year because … there wasn’t any! Having proven to myself that it would grow in 2007, I decided to use my limited space for other groovy crops. And that’s an important thing about sweet corn – if you are growing veggies for profit, corn is on the low side for profit-per-square-foot of garden.

On the other hand, a patch of corn looks really impressive in a small vegetable plot. Hope you will come back when I have more. :)


goodgrowing, June 2, 2009
Hi Wendy et al.!

Kevin Belluz here from the aforementioned Belluz Farms. We use a number of tricks to get early corn on our farm including selecting early, good cold soil germinating SE varities, planting very shallow, and covering the first 2 acres with a clear mulch (materbi biodegrad.). The earliest we’ve seen is around August 4th, and regularly around August 10th. Last year’s cold summer saw delay until late August. That can cause a lot of stress since we plant 4 dates (about 12 varieties) to space out harvest over 4-5 weeks and starting late August means we’re bound to lose some to frost which can come as early as September 5th… Luckily, last year we didn’t have killing frost until late and got about 80% of the sweet corn picked. Ahh, northern growing. Our main pests are Corn earworms(some years armyworm). They don’t overwinter here and all come in on the winds (not everyone realizes we’ve had free trade on the farm for centuries). This causes quite a problem some years because there’s no natural build up of the pest for scouting to monitor, just a massive influx one night. We use spinosad as our primary control when needed and everything is hand picked and inspected before going in the bag. I’ve tried convincing customers that if they find a worm the extra protein is free, but have had little success…

Growing since 1946, it is nice to see a resurgence in interest for locally grown produce. It really is making our lives a little better on the farm and takes some pressure off the marketing department (me and Jodi!) to feel like we need to hammer people over the head to tell them the berries are ready, the berries are ready! We only hope that all growers are approaching the business as the profession it is and growing and marketing their products responsibly. We need more farmers in the world and that can only happen if it is a reasonably profitable way to make a living which requires consistent quality, fair prices, and high levels of food safety.

Keep up the good growing everybody!


Wendy (author), June 3, 2009
Hi Kevin!

Thank you for your informative post. This gives us all some guidance, and corrects me in my error of thinking that sweet corn was not available here until the end of August. Glad the clear mulch works so well – August 4th – wow!

I looked up Spinosad and it sounds like just the thing – low toxicity to mammals, and quite specifically toxic to the caterpillars it’s targetted towards. Wikipedia says it’s good against sawfly larvae as well – I wonder if I could get my hands on some of it for my roses? :-)

As a loyal customer of your corn stand at the market, I can vouch for the fact that your pest control and quality assurance practices work – I’ve never found an insect in Belluz corn. As a marketer I, too, have tried the “extra protein” quip with customers, but it’s better when it’s not necessary (customers never seemed to find it as funny as I did).

It really is heartening how local produce marketing is growing. Small-to-medium farms are in for better times.

Thanks again for your inspiring contribution.


Wendy (author), June 3, 2009
Me again – a good overview of sweet corn pests and controls is available at, McGill University’s Ecological Agriculture Projects site.

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