This is a continuation of the
previous post, which was getting long.
Growing degree days (GDDs) can be used to examine the challenges of growing some kinds of corn in cooler climates. As I mentioned last time, I've been growing mostly Blue Clarage, which is about a 100-day corn;
Chad Lee's presentation suggests that about 2400 GDDs are needed to get the crop to maturity; last year I harvested at 2677. I planted the first week of June (Georgia has a pretty long growing season). If you live in a cooler climate, you might have a hard time growing a 100-day corn. For example, in 2014, there were only about 2000 GDDs in Presque Isle, ME--for the entire growing season. Leadville, CO got about 1200, but probably everyone understands that not much can be grown at 10,000 feet in the Colorado Rockies. Coeur D'Alene, ID was a little better last year; just over 2500, but that's not much margin for error--especially considering that frost in May is common there. Had you planted June 1, the remaining GDDs would've been more like 2000.
So in colder climes, flint and sometimes flour corn are more commonly grown. Anthony Boutard has written a book titled,
"Beautiful Corn" that I should've linked to last time, in which he discusses the different varieties of corn and the places / climates they are grown. He is also featured in a few videos on YouTube:
A Farmer and His Corn,
A Sustainable Farmer Talks Corn,
A Cornfield in Winter, and others. He mentions Blue Clarage in his book, as well as Oaxacan Green, another type I have grown, but doesn't say much about them (he wasn't impressed with Oaxacan Green, and neither was I the one year that I tried it). Most flints seem to be around 90-100 days, i.e., probably about 2200-2400 GDDs--not all that much less than some dents. However, at least one seed vendor sells a variety,
Gaspe Flint, with a claimed 45-60 days (GDD equivalent would be... not much--maybe 1400-1670 GDDs? That's a slightly informed guess based on Chad Lee's figures, which are not completely linear. I just did a quick OLS regression, but I think that's close enough for now). That would still be marginal at best for Leadville, but would work fine for much of New England--where flints have been grown for a long time--and the northern tier of states out west.
I don't need to explore flint corn all that much, and I think given what I'm using my corn for, dent is better--so far I have mostly made cornbread with it, though after a visit to Paula Deen's restaurant in Savannah, I tried to do hoecakes--hers were better. So cornbread it is for now.
Earlier I mentioned that small stands need to be more intensively managed. That's mostly because of pollination issues. Corn is wind pollinated, though as the photos below show, bees do like corn pollen--they just aren't interested in spreading it to the silks.
Corn tassels are visible quite some time before pollination actually occurs. When the tassel starts shedding pollen, you'll see anthers (visible as dangly things hanging off the tassel in the picture below) drop down. They'll shed pollen for at least a few days to a week, and often they will start shedding a few days before silks emerge--which can cause great consternation. When the silks begin to emerge, they will be receptive to pollen for a few days. If you have just a few plants, you can't count on getting good kernel set if you let nature take its course, so you can force the issue.
At Pioneer, we would put shoot bags on the emerging shoots (which would later turn into ears) before silk emergence. The shoot bags look like little coin envelopes but are a much lighter-weight paper. When the silks finally broke through--we checked each plant each day--we would bag the tassel with something that looked like a lunch sack. On each sack the crop heat units (CHUs, analogous to GDDs) accumulated as of the day before would be stamped to enable the nursery staff to chart that aspect of each variety's development.
We would leave the tassel bag up for one day, then the next afternoon slap it a couple of times and undo it carefully (so as not to dump the pollen prematurely), then pull off the shoot bag as we upended the tassel bag over the shoot. It was a little more complicated than that, with a few additional quality control measures, but basically that was it.
That process wouldn't necessarily work well for a home gardener. In the first place, if you're growing open-pollinated corn, you probably have at least some interest in keeping seed and planting it in the future (though with few plants in the ground, you'll suffer inbreeding yield loss if you do that for very many generations). So you don't necessarily want plant A's pollen to go on plant A's silks, but when A is shedding pollen plant B might not have entered R1 yet. What I have done with small plantings is go out at dusk with a simple 8 1/2 x 11 sheet of paper, folded in the middle to make a crease, then opened back up. I tap the branches of the tassels shedding pollen onto the paper, then the fold helps me dump the pollen I get from the tapping onto whatever silks are ready to be pollinated that day. I do this nightly, hitting silks on various plants more than once over several days, until there's no more pollen being shed. At dusk the wind usually seems to be muted here, so that helps control things. Too much wind would make it difficult to get pollen onto the paper. When you tap a tassel over a plain white sheet of paper, you'll be able to see the corn pollen if there is any: it's bright yellow. Eventually the anthers will run out of pollen; they may still be dangling but they'll be translucent--after you look at a few in varying states, it'll be easy to tell when a tassel is pretty much done. Since corn is a wind pollinated plant, the pollen granules are also microscopically barbed, so the the paper also needs to be tapped a bit to get the pollen off the paper onto the silks. The pollen also hooks into people; I used to itch terribly during pollen season. I was the only pollinator who wore long sleeves in the field, but still had some troubles. It also has a pronounced fragrance...
Anyway. Pollinating your plants yourself, you can get filled out ears even if you only have a few stalks growing. It really is not much trouble. If you want to take a hands-off approach and rely on the wind, there are things you can do to improve kernel set. Planting corn in rectangular blocks helps with wind pollination. If you want to have about 30 row feet of corn, plant 6 rows of 5 feet each, 4 rows of 8 feet, or something similar instead of one or two longer rows. Corn can also be planted in hills, with small groups of plants every few feet. I have never done this, but the concept seems to be pretty reasonable. Basically, you just want to do what you can to ensure that the wind helps pollinate the crop, regardless of what direction it's coming from.
As shown at right, I had three rows that were about six feet long each. My corn was too crowded, because I didn't thin aggressively enough. So I had to give them water and fertilizer (mostly blood meal), more so than I would have had to if they had been planted with wider spacing.
I figured this plant arrangement was good enough for pollination, so didn't do anything for them myself. Blue Clarage usually sets one ear per stalk; often there are two. Sometimes there will be a third shoot, but it in my experience it never amounts to much of anything. This is fine. I got the collection of ears shown at the left from the plot above. There's one completely undeveloped ear that I included just to show what it looked like. Most of my ears were pretty full, except for the tips. I was pleased.
As noted in the first part, there are a few pest and disease issues. I have never had to deal with smut, for which I'm glad. I did get a fair amount of rust last summer. When I watered the corn--which, as I said, I had to do because it was planted too close together--I used an overhead sprinkler. People tell you not to wet the foliage when watering, but I figured rain wets it, so I can, too. It was easier to do it that way than to thread a soaker hose in between the rows or come up with another approach. So the leaves did get wet whenever I watered, but that was only once per week during dry spells. The late summer was very dry last year, so there was a lot of watering. Rust can cut yields, according to some ag extension sites, so I did try treating with daconil a couple of times, to no apparent effect. The yield was still okay.
I did have problems with stink bugs. Brown marmorated stink bugs (BMSB) are moving into this area, and they like corn. There are also native brown and green stink bugs; the differences between the native brown stink bugs and BMSB are subtle, as shown
here Mostly I had brown ones, but I found a few green stink bugs on the plants, too. They suck juice out of the kernels. At right is a closeup of some of the ears; the mottled macerated-looking kernels were attacked by stink bugs. I'm assuming they (the kernels) will be okay since the wretched beasts excrete their foul juice from their abdomens--any of that went on the shucks, which were disposed of.
How to deal with stink bugs? You can spray an insecticide like Sevin, spinosad, or malathion; I just went out there at least once a day with a can filled with soapy water. I was pretty successful at getting them into the can, where they soon drowned. I would say I found on average about 20 per afternoon / evening every day for about three weeks; then the corn reached a dry enough stage that the stink bugs were no longer all that interested.
The
UGA guidance gives different thresholds at which treatment is recommended (they suggest different insecticides; the target audience is commercial growers). I definitely had stink bugs present in numbers that would have warranted chemical controls if replicated across an entire field.
BMSB are going to become more prevalent in Georgia in coming years, so pest management will be a bigger issue with corn going forward.
I usually have blight problems--generally early blight. This year the blight is more limited. Generally my tomatoes are pretty well done by now, but then they get a second wind in September and I end up with some green ones at the time of first frost. This year I'm still getting tomatoes in mid-August and will dehydrate them, as well.
Last year--for the first and only time ever--I had some tobacco hornworms and saw one that had been turned into a host by parasitical wasps. Very gruesome, but I was happy to help the biological controls work. Otherwise, the hornworms haven't been a major problem, either. 
