How To Pollinate Corn Plants: Corn Pollination

Details on how to pollinate corn, when to pollinate and how to tell if corn is pollinated are given below.

Corn or maize is a monoecious plant, it has both the male (tassels) and female (silks and ear) reproductive parts flowers are present on the same plant [1, 2]. The ear is the female flower of the corn plant. The tassels emerge from the flowers on the top of the corn plant, and the silk or hair (stigmas) and ears emerge on the rest of  the plant.

Silks start to emerge from kernels at the base of the ear and move up. Each one of the female silk are attached to a kernel inside the stalk. How to grow corn from seed

Corn Female Flower showing Silks. Each silk needs to be pollinated

How Corn is Pollinated?

Corn Male Flower

1. Corns are pollinated by wind. When the tassel ripens, pollen is shed downward on the silks of the immature corn ear to get pollinated. Each one of those silks need to be pollinated for the kernel to grow. The small hair on the silk help to capture pollens falling on it.
2. The colour of the pollen is yellow and the pollen grain remains viable up to about 2 days. Maximum pollen is shed by the 3rd day and the shed may last up to 7 days.
3. A silk can grow 1 to 1.5 inches per day until pollination occurs. When each one is adequately pollinated, you will have a beautiful full ear of corn with rows of kernels.
4. If a silk does not receive a grain of pollen, no kernel will form in that space on the ear, creating an empty space. This way about 500 kernels are produced on an ear.
5. Pollination starts 2-3 days after silk emergence and continues for about a month. Silks that are still attached to the kernel are yet to be pollinated. 
6. Synchronous pollination within and between ear improves kernel set in corn [3].

Pollination By Bees

Can bees pollinate corns? Bees are not needed for corn pollination, but when the wind is calm, honey bees may help pollination. As the bees move through the corn tassels, they release pollen that may land on the silks of the female flowers to  pollinate them.

When To Hand Pollinate Corn?

The important point to consider is the correct timing of hand pollination. First the silk emerges from the embryonic ears, after 2-3 days tassels begin to open. You cannot hand pollinate until the tassels are fully open and beginning to shed the yellow pollen. Start hand pollination as soon as the silk emerges.

Corn Hand Pollination Method

In corn farms, the corns are pollinated by wind. But in the home garden, often pollination becomes problem only by wind, and you may grow only empty corn ears. You can sow corn in blocks in your home garden. This way there will a better chance for pollen to land on a silk by wind.

You can use following hand pollination methods to pollinate your corns.

1. When the tassels have opened and silks have emerged, just shaking the plant will improve pollination.
2. Hold a paper under the tassels and shake the tassels onto the paper to collect on it. Then drop the pollen on the silk hairs to pollinate them.
3. Collect the Corn Pollens: Another way to hand pollinate corn is to use a small paper bag and collect pollens in it. Just slightly bend the tassel into the paper bag. Shake the tassel to collect pollen. Then pour the pollen onto the silks.
4. You can cut off a tassel and wipe it on the silks several times to pollinate them. One tassel can be used to pollinate several ears of the same type of corns.

Corn Tassel with anthers visible on central spike

The above picture shows magnified view of corn tassel with visible pollens on the spike, whcih can be ised to hand pollinate silks.

Corn pollination by hand, Wipe a tassel on the silks several times

Important Points for Corn Hand Pollination

1. Repeat the hand pollination for every plant for about 10 days. 
2. If it rains for a day or longer, you have to hand pollinate again.

Ways to Know if Corn is Pollinated

There are three ways to determine if your corn has been pollinated successfully.

1. Un-pollinated silks are white in colour. When corn has been pollinated, the silks will turn brown in colour, they dry up and fall off. 
2. Open the husk slightly at the top of the ear. Now shake the ear, if the darkened silks fall out, indicating corn pollination. 
3. Slightly pull back the husk and examine the ear after 10–12 days after pollination. If successfully pollinated, you will see white kernel like blisters or ovules.

Poor Pollination, No Pollination or Empty Corn Ears

Many times the corns are not pollinated, or poorly pollinated and you get partially empty ears/cobs with missing kernels because of the following reasons:

1. The pollens are shedding but the silk has yet not emerged. Under ideal conditions, by the time the tassels open, the silks should have emerged to get pollinated. But sometimes it may not happen due to many factors such as heat, lack of water, excessive water, lack of sunshine, plant disease, nitrogen deficiency, etc. Dry hot conditions can reduce pollen viability.
2. Corns are pollinated by wind and if the corns are planted quite far from each other, then the pollens do not fall on the silk.
3. During continuous wet conditions, anthers will not open to shed pollen, so pollination does not occur.
4. If the ears of your corn have blank sections on it, this shows inadequate pollination.

Can Corn Cross-Pollinate?

Corn self-pollinated or cross-pollinated?

1. The corn plants are both self-pollinated and cross-pollinated by wind. In home garden, the corn plants have kernels mostly by self-pollination. But only 5% of kernels in a corn plant growing in a field are self-pollinated and more than 95% kernels are pollinated by other  plants. 
2. All types of corn are able to cross-pollinate, that means the sweet corn can get pollinated by field corn or by ornamental Indian corn (Indian corn, Calico corn, and Flint corn), and this is true for other types of corns. Such cross-pollinated corns will produce ears having kernels of different types. 
3. It is therefore better to isolate different types of corns from each other, which is possible only in the home garden. In the field, as the vast amounts of pollen are transported in wind, it is difficult to avoid cross-pollination, unless only one corn variety is grown in the field.

References

1. Nielsen, R.L. 2010. Silk Development and Emergence in Corn
2. Nielsen, R.L. 2010. Tassel emergence and pollen shed
3. Cárcova, J., Uribelarrea, M, Borrás, L., Otegui, M.E., and Westgate, M.E. 2000. Synchronous pollination within and between ear improves kernel set in maize. Crop Sci. 40:1056-1061

Video on Growing Corn

How to pollinate corn plants
How to grow corn from kernels at home