Questions on: Corn

Ron Smith, Horticulturist, NDSU Extension Service


Q: I've heard that if you cut the top off corn, it will grow taller and produce more. Is this true and where do you cut it? Also, half my corn stalks are tall and the other half short. It's like going down the line from tallest to shortest. What causes this problem? (e-mail reference)

A: I have grown corn for commercial purposes and worked for farmers who did the same. We never cut the tops off because it makes no sense if you understand the growth of monocots, which corn happens to be. The problem could be water or nutrient availability or sunlight exposure. Something in the environment is not uniform.


Q: Is it possible for dead corn stalks (used for decoration) to emit pollen? (e-mail reference)

A: I really doubt it because the pollen was dispersed long ago. The likelihood of any being left is very remote. Also, it is very dense pollen by comparison, so the pollen would have washed away or decayed by now.


Q: We planted four long rows of corn this year. The ears ended up being very short or what you call nubbins. The bees worked hard on pollinating the corn. What am I doing wrong? (e-mail reference)

A: Instead of planting four long rows, try planting eight short rows next year. Obviously the pollen, which is wind driven, did not reach the silk in sufficient quantity to fill out the ears. I think if you alter your planting next year to a more block system, the results will be much better.


Q: This summer my corn had a white and yellowish foamy substance shooting out of the plant. Some sections looked like the “insulation foam in the can” you get from your local hardware store. Some of the plants fell over and at least half of my sweet corn was infected. What is the disease? (e-mail reference)

A: You had corn smut (Ustilago maydis), a common fungus disease of sweet corn, popcorn and field corn. In Mexico, it is considered a culinary treat. If you have any Mexican restaurants in your area, you might contact them to see if they would be interested in purchasing some. You could make more money selling it for ethnic cuisine than as straight sweet corn. No sprays are available to alleviate the problem, so try to find varieties/cultivars that are bred for resistance and clean up the garden.


Q: Can one corn stalk grow alone where no other corn is planted? (E-mail reference)

A: You can grow just one corn plant but you need to take the pollen from the tassel and dust it on the silk. Full-size ears will not develop unless you do that. It will grow as long as the seed is viable (alive), has adequate warmth, light, water and nutrients.


Q: I know a family that wants to grow sweet corn for local farmers’ markets. They want to plant a number of different varieties but are worried about cross pollination. What distance is needed to avoid cross pollination? (Cavalier, N.D.)

A: Sometimes the maturity of the different varieties of corn will prevent cross pollination. If that isn't the case, then as much distance as possible needs to be kept between the varieties, sometimes as much as 500 feet since corn is a wind-pollinated crop. I’m grossly dating myself now, but I grew an acre of sweet corn for market purposes when I had my small farm in New York. I simply planted three varieties -- early, mid-season and late. By the time the early one tasseled out and fertilized the ears, the mid-season was just starting to tassel.


Q: I have a question about so much smut on the sweet corn. We have been getting sweet corn from my wife's brother. He has a good size plot and likes to raise corn and give it away to his friends. He was quite concerned about the problem of smut this year. He has had different maturity corn but I don't know the seed company. The last corn we got was a later maturity and it had a thinner ear, smaller kernels and a few white kernels. It was just maturing. Could have used a couple more days but it was good. The amazing thing was it had very little smut. Next to none. Could the later maturity have something to do with this? (Breckenridge, Minn.)

A: Corn smut thrives in warm weather, with the optimum being in the 80 to 90 degree F range. The best control is to follow good sanitation practices and plant corn hybrids noted for good vigor and resistance to this fungus. Crop rotation may help somewhat, although it can be spread via birds and insects from other adjacent areas.


Q: Does a corn stalk just produce one corn cob? (Napoleon, N.D.)

A: Corn stalks often produce at least two, sometimes three, cobs. The second and third ones are smaller, sometimes down to the "nubbin" size, but still good eating.


Q: I have a lady who says she has raised sweet corn all her life and has never had this problem. The corn in her garden has tiny black flies on the tassels. I thought it was just a fly that was attracted to the tassels and would do no harm. (Steele, N.D.)

A: They are likely confused chinch bugs that should be feeding on the leaves but perhaps find the silk more tasty. If they are truly flies, then I think they are going after the "nectar" on the silk and are nothing to worry about.


Q: I would like to know why I have not been able to grow corn for about the past four years. I can only get four sprouts from two packages of seed. Previously, I have had great success. I have had the same garden spot for 20 years and rotate my crops religiously I also have fertilized with urea, but not consistently. (Lansford, N.D., e-mail)

A: Why won't your corn grow now where is has grown in the past? Low sunlight? Too cold or wet? Birds get the seed? Cutworms? Old seed? Late frost? Herbicide residue?

I cannot think of any other possibility than what I've listed here. Why not try a different variety? There are several great ones out there.


Q: What chemical product can be used to control weeds and thrips in a plot of gladiolas? I prefer to garden organically, but I am also having problems with weeds in a plot of sweet corn. (Lake Benton, Minn.)

A: You'll have a tough time controlling thrips in your glads organically. I have never been successful. You can try insecticidal soap if there are no predatory insects present. Otherwise, use Orthene (a contact/systemic) to control them.

I would suggest presprouting the weed seed and killing off the seedlings with Roundup. Or, you may want to try solarizing the area by covering it with heavy clear plastic for about two weeks prior to planting. The weeds will sprout and stay soft, with some drying. Those that don't are easily rogued out when the plastic is removed. Plant your sweet corn close. Hand cultivate while canopy is open (usually until July 4th or so) then let them go. The corn will form a dense enough canopy so that the weeds beneath it will be weak enough to be noncompetitive. Otherwise, there are many herbicides that canbe used in sweet corn.


Q: Can you tell me what is wrong with my corn plant? The bottom leaves are turning brown and yellow and I don't know why. I also have a cacti, but I don't know if it is a Christmas or an Easter cactus. Is there a big difference between the two? (Enderlin, N.D.)

A: The corn plant could probably stand to be propagated. Cut the plant back to about a 6-inch stub, then cut the removed trunk into roughly 4-inch-long pieces. Place them on their sides in damp sphagnum peat, and in about six weeks or so new growth should be evident. Repot the mother plant in fresh potting soil in a free-draining container. Refer to "Home Propagation Techniques" (NCR274).

Yes, the two cacti are different. They are either different species of the same genus, depending on the taxonomist you wish to go with. To me, they will always be different species: Schlumbergera truncata (Christmas cactus) and S. gaertneri (Easter cactus).


Q: Please find enclosed some leaves from my corn plant, it is over 6 feet tall and 10 years old. The leaves have started getting brown and turning yellow, then brown and leathery. The stem turns to a bark looking covering from the bottom where most of the leaves turn brown. I have it in a large pot, and I try to keep it moist. Should I repot, or what should I do? (Cleveland, N.D.)

A: Refer to NCR publication No. 274, "Home Propagation." I want to suggest that you may wish to propagate this if the plant does not recover from repotting.

The cause of your plant problem could either be too much water during the winter or the plant has been exposed to too many cold drafts. When you repot, make sure it is into a free-draining container and that it can be located where cold cannot reach it. 


Q. What kind of chemical could I use in planting sweet corn for weed control whether or not it is a pre-emergence or post-emergence.. What kind of chemical could I use for purslane control in my sweet corn? (Wahpeton, N.D.)

A. Treflan is the most common weed control (pre-emergence) for most vegetables (tomatoes, beans, peppers, mustard, carrots, cabbage, etc.), but not for corn. Prowl can be used on sweet corn for controlling many weeds like foxtails, crabgrass, barnyardgrass, purslane, spurge and kochia.

The active ingredient in Prowl is pendimethalin, also commonly found in turfgrass weed control products.

Thanks for writing.


Q. We have our sweet corn patch on part of a barnyard that is infested with all varieties of weeds. Is there any kind of spray that can be used that will not harm sweet corn plants? We do cultivate with the tractor, but need something to control the weeds in the rows. (Pelican Rapids, Minn.)

A. You ask a simple question, but the answer is difficult to come up with. Here are some options I can suggest.

1. Allow weeds in area to sprout, then kill down with Roundup.

2. Basagran and 2,4-D are the only non-restricted use products that you can use for broadleaf control.

3. Prowl, Eradicane and Pendimethalin products are non-restricted for grassy weed control.

You may want to try crop rotations to help keep the weed
population down.


Q: I remember someone talking about how a person can grow baby corn on the cob. My husband and I have been having a discussion about this. I think I
remember that they are just immature regular corn with the silk removed. He thinks that there has to be a dwarf corn plant that produces more than one ear per
plant. I would like to try growing baby corn ears. Do you have any suggestions? Can you tell me how to go about it? (Grand Forks, N.D., e-mail)

A: Simply plant your corn and harvest it before it silks. To keep it from becoming fertilized, you can remove the tassel, which is the source of the pollen.
Then simply harvest the sweet, edible, small cobs that develop. Couldn't be easier. Enjoy!


Q: A recent column of yours included a discussion about baby corn. Let me relate my experiences. The first time I planted several rows about 20 feet long. The
more you pick it, the more it produces. I'd get a big wheel barrow full at a time. You can't husk tiny, tender ears. It's best to cut a slit down to the ear and lift it out.
Out of that wheel barrow, I'd get only about two quarts. It was too time consuming to continue all summer, so I pulled the stalks before they had a chance to
produce the 40 ears, as advertised. The next year I planted 15 seeds, just enough for a meal at a time or to freeze for a meal. They need to be picked every second
or third day. (e-mail)

A: Thanks for the input on the baby corn. I have seen those miniatures advertised but knew that the same basic end result could be achieved via my
method. It is wise of you to cut back on your planting the following year. It is one thing to like something, but to be overwhelmed with it is no pleasure!


Q: I have a question about what appears to be a fungus on some sweet corn stalks. At first small spots show up on the leaves. The spots are about 3 to 5 mm in
diameter and of a light cream color. Later a fungus like growth shows up where the leaf and stalk join. This growth later becomes thickened and continues to spread
along the main stalk. Is there any product that can be applied to control or prevent this? Last year I also had some problems with the formation of the dark smut. It
has dark blue/black appearance. Do you have any suggestions about what can be used for this? Thanks again for your help. (E-mail reference, Faulkton S.D.)

A: That is known as corn smut or Ustilago maydis, for which there is no cure or useful spray. It occurs when the temperature is in the 80's and 90's,
and we are experiencing wet, humid weather. It saps the energy from the corn plant, reducing ear development. The best way to handle this is to cut off
the galls before they release the black powdery spores, plant varieties of corn known to be resistant to smut, and finally follow good garden sanitation,
cleaning up all debris in the fall. Do not use manure in your soil if this continues to be a problem.


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