Adapting Corn to Your Place: Isolation and Promiscuous Pollination

Reader Contribution by Pamela Sherman
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If we want to grow more than one variety of corn in the same season, which besotted corn-lovers may wish to do, how do we keep them from cross-pollinating? Do we ever want them to cross? It depends what we’re after.

By talking to growers who grew the seed, then saving seed each year and replanting it, we see how each variety does where we live. Are we satisfied that each of our varieties has the genetic resilience it needs? We can tell this by how well it does with respect to the weather, local conditions such as soil and topography, air quality, pest and disease control, and the needs and taste preferences of our family and whomever else we are growing for.

We are the ones who decide what we mean by “how well it does.” Does each variety produce strong stalks that don’t fall over in our winds, mature within our season’s length, get enough sun, etc, and make us swoon with its flavor and aroma? What else is important to us personally in home corn growing? If we are satisfied that each variety does as well as we’d like, we’ll want to keep our varieties separate so they don’t cross-pollinate.

With corn, each kernel is pollinated separately, so even if a few kernels are cross-pollinated, is that ok with us? Some gardeners welcome that as a whimsy, an experiment, a welcome sign of diversity; others prefer perfectly pure strains. There is no right or wrong here.

Adapting our corn means taking our own desires into account. There is not only room for every shade of opinion, but the community of organic corn gardeners needs every opinio, every shade of grey, every different point of view. This way we get to see the ongoing consequences of each different way of thinking and doing. Genetic diversity in our corn depends on the diversity of mind of the corn gardener and gardening community.

If we are happy with our varieties the way they are, we may choose to isolate each corn variety from the other(s). Some ways to do this are:

Isolate by Distance.

Some seed-people advise separating the varieties by 2-300 feet, some say by 1-2 miles. I’ve been told that the corn pollen prefers to just hang around its own home stalks, but wind will carry it wherever. How far we think we should space our varieties from each other depends on our area, our topography, our wind strength, frequency, and direction etc. Perhaps there’s a neighbor just the right distance away who’d be tickled to grow our other corn variety?

Isolate by time.

Choose varieties in which the pollen does not mature at the same time, so cross-pollination isn’t an issue.

We Can Be the Wind.

Cover the tassels of one (or more) varieties with bags before they release their pollen. (Knowing when the plant is starting to release pollen requires watching the tassels as they grow. After a while, we can get a feel for it, as we get to know our plant and its needs better.) After the tassels poof their pollen into the bag, we can then gently release pollen from the bag onto the silks of neighboring stalks’ ears. Plants don’t all poof pollen at the same time, so continued attention is needed until pollination for that variety is played out.

In-breeding Depression

One important thing about growing all corns is: they like company. If they don’t have enough other corn to cross-pollinate with, they get depressed and produce poorly (yield, ear and kernels are not up to snuff.). It’s called inbreeding depression and comes from a gene pool that’s too narrow. To avoid this, common wisdom says to plant at least 200 kernels of each variety. When we save seed at or after harvest, we should be sure save kernels from 200 different stalks.

What if we don’t have the space to grow 200 stalks of corn? We could buy more seeds of the same variety and mix ’em up with ours for next year’s planting, giving away the rest. We could get together with enough other friends or neighbors growing the same variety to make at least 200 plants total and mix our seeds up together. That will maintain or widen the genetics of the variety.

When given enough community, corn has huge genetic variation and is therefore one of the most adaptable of plants to all kinds of weather extremes and conditions.

Cross-Pollinating

What if we want characteristics of two or more varieties on the same plant? What if we want to play a little and see what corn qualities might appear that we never knew existed, that no one ever knew existed? This is where seed-saving gets fun. Plant two or more varieties together, totaling at least 200 plants. Then inbreeding depression is not an issue.

For the maximum wow factor, I, like many others, take inspiration from the corn breeding of Joseph Lofthouse internationally-recognized master seedsman, and Mother Earth News blogger. His way of growing corn, to me, produces results that are like getting the most useful and fascinating variety of gifts at the biggest birthday party ever. 

As one website states: “Joseph’s style of landrace gardening can best be summed up as throwing a lot of varieties into a field, allowing them to promiscuously cross pollinate, and then through a combination of survival-of-the-fittest and farmer-directed selection saving seeds year after year to arrive at a locally-adapted genetically-diverse population that thrives because it is closely tied to the land, the weather, the pests, and the farmer’s and community’s habits and tastes.” 

As Joseph states: “I am fond of saying that there is more diversity in a single ear of any of my corns than there is in a hundred acre field of industrialized corn. My strategy for avoiding inbreeding depression in corn, is: 

All of my varieties started by combining hundreds of varieties into a single strain. 
I plant hundreds to tens of thousands of seeds for each variety. 
I plant a bit of older seed along with the newer seed. 
I allow a bit of pollen drift between similar varieties. 
I swap seeds of similar varieties with my collaborators and plant them together.”

As gardeners, we can each interact with our corn like this on a smaller scale in our own way, over time, adapting to our own local situation, conditions, needs, and desires.

Photo by Joseph Waters


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