I often get questions about planting corn and corn cross-pollination. I’d always been taught that you had to be careful with corn, but for years I didn’t really know the “why”.
First, let’s talk about what corn cross-pollination is and why it is such a worry. Cross-pollination is the natural process where pollen from one variety of a plant pollinates the flower of another.
Cross-pollination usually only affects plants within the same family (to learn more about plant families read this post). So for example a zucchini can cross-pollinate with a pumpkin, but the results of the cross-pollination will not show up until the next generation. So it will be the offspring of the cross-pollination that will be a new plant. You will NOT get a pumpkinzini this year.
Anyone who says their (x) crossed with (X) and I got this weird funky fruit is mistaken. In those cases what really happened is they started out with bad seed or there was some environmental factor that made this year’s fruit “funky”. Strange fruit this year is not the result of cross-pollination this year. I repeat, cross-pollination affects the next generation fruit, not this year’s fruit in almost all families of veggies that can cross-pollinate.
BUT, corn cross-pollination is an exception to that rule. The corn that you get this year, can and will be affected by cross-pollination. So you have to be careful what types of corn you plant in your garden.
It all has to do with Dominant Genes.
Field corn and Popcorn are always dominant to sweet corn.
Also, regular old sweet corn (or even heirloom sweet corn) may be dominant to many of the “super sweet” varieties of corn out there on the market.
So what does this mean to the home gardener?
Corn is wind-pollinated, which means the pollen is spread almost exclusively by the wind (No Insects Involved).
Corn plants are pollinated when they “tassel”. Tasseling is when you see the tall feather-like shoots at the top of your corn plant and the tassels contain the pollen (this is the male part of the plant). Lower on the plant is the female flower which we call silt’s.
These are the bunches of fine silk-like material that eventually will be at the top of your corn cobs. The pollen from the tassels is blown by the wind to the silts, where the seeds are then pollinated and eventually become each of the individual pieces of corn on the cob.
This is why it is so necessary for you to plant corn close together in blocks or multiple rows. So the pollen from one corn plant can spread to another.
This also explains why it is so easy for different varieties of corn to cross-pollinate.
So let’s use sweet corn and popcorn as an example. If you plant sweet corn and popcorn together, popcorn is the dominant gene. So if (and when) pollen from your popcorn gets on the silt of your sweet corn, cross-pollination will occur and the dominant genes in the popcorn will ruin your sweet corn, giving it a “funky” stranger-tasting corn.
So how do you prevent this corn cross-pollination?
There are 3 methods.
1. Only plant one variety of corn per year.
If you want sweet corn, then choose one variety of sweet corn that year so there is no risk of corn cross-pollination. And make sure if your neighbors garden (anyone within 100 feet of your garden) that they also plant the same or a similar variety of sweet corn. Yes, fences or large buildings between your garden and your neighbors will help, but they are no guarantee.
2. Distance
Distance between varieties can prevent corn cross-pollination. 100 feet is usually considered enough distance to prevent any significant cross-pollination. A house between (or some other large structure) may also help. But if you want 100% pure seed (for example if you are planning on saving an heirloom seed for next year). Then really 1000 feet is the max safety zone!
3. Time
The other method for preventing corn cross-pollination is timing. The way this works is you separate the time different varieties are pollinating by planting those varieties at very different times. Say at least 3 or 4 weeks apart. This means that one variety is done pollinating before the other starts setting tassels.
Separation by time can also be accomplished by planting varieties with vastly different tasseling times. Try planting an early-maturing sweet corn with late-maturing popcorn. This one requires you do some homework and may also mean a little trial and error for a few years.
I understand this corn cross-pollination is a bit complicated, and it can also be a bit of a pain in the neck. Do your research before you plant different varieties of sweet corn together to be sure they won’t cross. And remember that you can never plant popcorn or field corn (Including those fancy colored decorative corn) together with sweet corn.
Questions??? Ask away in the comment section!
My husband and I were just talking about this yesterday!
Thanks for the info on how far apart the two different crops should be.
Do you have the same info on other types of crops that can cross pollinate too? Like the example you gave with the zucchini and pumpkin?
Hiya Rick,
I know this was an ice age ago relative to MT (my time 2021) but these things last forever as long as you keep up your hosting. Ha. Thanks for doing my research for me. Been plowing the same 60×80 for better than 40 years and I never really nailed down the corn cross pollination thing until I read your piece. Is it only for next year or this year. You answered the question. Also you jes gave me a fright.
I decided this year to plant a couple of rows of a super sweet with my all time fav Golden Queen.First time in a loooong time to try a different variety. I see I will have to stagger. Again thanka for that tid of smarts! The scary part is my neighbor, an import from Guatemala, just planted some kind of crazy Mexican field corn. If that stuff happens to tassel at the same time as my Golden Queen then I will have a problem. Dang! Guess I have some homework to do on my planting times now. He planted yesterday so I have to make darn sure to miss his tassel.
I consider myself very smart for looking you up!
Your bestest fan in Alabam
Norm
Norm,
I’m glad I could help! Good Luck!
You could hand pollinate and use corn ear shoot bags. Maybe not on all of it, but on a handful if you really want the corn to be true to type if his tassels at the same time as yours (or if both of yours tassel at the same time). They also have bags for the tassels to isolate and collect pollen but I think only seed savers go to that extent.
Basically you cover the ear as soon as it appears and when the pollen is ready, remove the bag, pollinate and replace the bag, making sure it’s secure. Some trim the silks so they are in a neat circle and pollinate the cut end.
Hope this is useful.
Many years ago I worked on a corn research farm I Florida as a field laborer. We had several different varieties of corn on 200 acres, 1/4 mile long rows. We would cut the tip of the ear when it was small and no silk showing and put a plastic cover bag over it. And at a certain point we would put paper lunch bags over the tassels when they were getting ready to flower and staple it closed to catch the pollen.. in a few days, we’d go back and shake the bag to collect the pollen and then sprinkle the pollen on the then showing silk and recover the ear. We also did cross pollination that way.
What an interesting job!
Is there some way i might be able to manipulate the sweet corn i have growing in my small garden , i have a rather complex situation i didnt know i was creating when i did thanks to rabbits or a rabbit going right down the row on a couple of rows and then not knowing about the possible results of planting a different variety , still sweet corn , i thought i was doing something smart by picking a variety that had a shorter grow period hoping for it to tassel at the same time but i didnt stop there i think to give myself a chance for maybe half the corn to be pollinated i have 4 varieties all in the same small garden and no row is all one variety but i have a pretty good idea of which individual plants are of the same variety right now its fairly obvious because of the size of the plants being bigger from the first planting and so on , can i be the wind help my odds any and can a corn plant self pollinate or does it take at least 2 plants to get any corn ? Last year 4 rows 20 to 25 feet long a couple feet apart gave me real good results , the rabbits found somewhere else to mess things up. This could be the last chance i have to grow my own sweetcorn so anything i could try to salvage as much as possible ill gladly give a shot, thanks.
If they are all sweet corn varieties they should be okay. they may not be as sweet as they could be, but the big problems come when you mix popcorn or field corn with sweet corn. That will ruin your sweet corn for sure.
Thank you for providing so much information, I’ve been trying to figure out how to plant two super sweet sweetcorn varieties – an F1 and a non-hybrid that I’d like to save seeds from if I like the corn.
You’ve got some excellent suggestions here, I’m going to follow as many as I can!
Thank you
You’re very welcome!
I live in Michigan and planted a small garden of peaches and cream sweet corn. 12 rows 10ft lg and 30 in. apart. About 2 weeks after my corn broke thru the ground the farmer behind my home planted field corn. 80 acres at least. I was told by someone that I could cut the tassels off to prevent cross pol. Is this possible. If so could you explain if this method works and how and when to do it? Thank you in advance for your help.
I’m sorry Roger, I don’t known anything about this method. In your case you will need to hope that you corn is done tastleing and has pollinated before the feild corn has tastled.
Planting Flint Corn, nothing else, a small behind the house patch. If I only plant blue seeds, as an example, will I get blue corn or will I still get multi-colored cobs, because the plants will produce a variety, no matter what. It’s controlled by what’s in the genetics.
If I only save one color seeds, the hypothetical blue, the next year, will I be more likely to get that same color, second generation, or would I be likely to just get a variety of colors, yet again?
Pete,
I’m afraid that is a little beyond my genetics knowledge. My assumption is that the genes that express the multi-colored cobs are still present in the blue seed, so assuming they are an open pollinated seed, and that you don’t have any crossing, you would still get plants that produce multi-colored seeds.
To get a complete blue ear of corn you would need to plant a seed that came from a plant that only produced blue seeds, or cross the right parents first.
But that is just coming from my Biology 101 knowledge of plant genetics.
I’m picking out the seeds by color, and last years plants, maybe 8, some came up all red, some came up mixed, some came up with nice mixed kind of translucent colors. Blue was just an easy example, since some are lite green, the usual white and yellow and some pretty lighter colors, not dark read.
Since I planted random seeds, that I germinated, I’ll need to start over and avoid anything from last year, which cross pollinated.
Your post was good to know why some had scattered seeds and big areas of nothing. Now I know that they didn’t get pollinated, and that was the cause, not just poor soil or bad watering.
I grow these for the experience and ornamental, so the fun continues.
Thank You
Will tall, thick evergreen or semi-evergreen hedgerows help reduce crossing between varieties on either side of the hedgerow? I’m aware it won’t eliminate it, as a pollen grain can sail through the trees, and it may even reduce in-variety pollination because you’re slowing down the wind, but it was just a thought.
Maybe someone could do a trial, if they have multiple maize paddocks, where some have hedgerows surrounding them and some don’t.
Thank you very much, your advice will be very useful as am still planting.
I planted sweet corn march 12 and it is about 3 feet tall. If I plant field corn close by it I shouldn’t have any cross pollination issues should I ? Today is may1. I haven’t planted the field corn yet but was waiting on the sweet corn to get ahead. Thanks James.
Yes as long as you are comfortable the field corn won’t tastle until the sweet corn is finished then it should be fine.