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You can avoid corn pollination failure

Many gardeners, especially new ones, are dismayed to find that the luscious ears of sweet corn that they expected look more like this:

Corn pollination failure

Failure to pollinate can drastically reduce yields of corn

Only a few kernals are present on  the cob!  All that hard work, fertilizer, watering, and all is just wasted!

(Please note that all the illustrations of corn pollination are with field corn, as I do not currently have room for sweet corn in our garden – a problem I’m working on – but the illustrations will work fine; all the principles are exactly the same.)

There are two main reasons why we have failure to pollinate: one is that the pollen is dead, and the other is that the pollen just did not reach the female flowers.

Dead pollen is common in years of extreme heat and drought during the pollen shed time for corn. Corn is rather unique among plants in that it is on an exact schedule from the day it is planted until the day it is harvested. When pollination time comes, whatever will happen will happen, and it only lasts a few days, after which the opportunity is gone. The corn will go on doing its thing, but all the inputs of the farmer or gardener are wasted if pollination doesn’t occur.

Corn is generally wind pollinated. Lack of wind can be a big factor in corn pollination. When one sultry day follows after another, corn pollination can fail.

A morning thunderstorm can do an immense amount of pollination in that first rush of wind before the rain starts. There is normally a flush of pollen shed in the morning just after the dew dries, and there may be another smaller discharge in the evening as the air cools. The male flower is the tassel at the top of the stalk.

An acquaintance of mine had a charter helicopter service in Illinois, and he was kept busy during the corn pollen shed, by contracting with farmers to provide wind for pollination. He would hover over the fields, moving up and down the rows – and got paid for it, because it was a valuable service for the farmers.


Corn just tasseling

Tassel just emerging on corn stalk; in the next few days it will produce 2-15 million grains of pollen

The pollen is produced inside the anthers:

Corn anthers

Hollow anthers hang down on threadlike stalks; pollen is produced inside

Gardeners generally have pollination problems for the second reason – pollen doesn’t reach the female flowers at the right time:

Corn silk ready

Corn silk is the female flower, which is receptive when fresh and green

The silk is the female flower which can be seen at the tip of the incipient ears on the side of the cornstalk. Each thread connects to a single incipient kernal on the ear. When it is green and tender, it is receptive, but it will turn brown in just a few days and the opportunity to pollinate is gone.

Corn pollen on silk

Pollen that falls onto the silk adheres

When a grain of pollen falls and sticks to one of the silks, it begins to grow a pollen tube down inside the silk strand, right to the incipient seed, which it then fertilizes.

The problem with garden pollination is that there are usually few plants; not a whole field; there is a limited amount of pollen available – and it may blow the wrong way. New gardeners are frequently advised to use four short rows, rather than one long row, for this reason. Corn planted in blocks does pollinate a bit better.

For even more pollination insurance, do it by hand – it only takes a minute. When tassels first appear, pollen shed is only a day or two away. If you look at the tassels in early morning light,  you can see the pollen, if you look toward the sun. If you shake a tassel there will be a visible dust from it, if it’s ready. If you shake it too hard, of course you’ll shake loose the anthers themselves.

So, when the tassels are ready, in the morning just after dew is mostly dry, bend a tassel over the silk (on another plant) and shake it.

Corn hand pollination

Hold the tassel over the silk and shake

Or you can snip a tassel and go down the row, “dusting” each silk. If you do it gently, focusing as much of the pollen on the silks as possible, you can do 10-15 ears for each tassel.

On bigger patches, you can simply walk the rows with your elbows out, so you give the stalks a bit of a jar, which will shake loose the pollen.

Some gardeners claim the process works better if you play soft music (but that may be a myth).

Corn is considered a wind pollinated plant. It’s pollen is tiny, and millions of grains are produced; only a small portion of them falling onto the female flowers.

Corn pollen on a leaf

Corn pollen shed is extravagent; much never makes to to the silks

Some falls on the leaves, some on the ground, and some will fall on your car hood, if you are downwind of a corn field.

Because the grains are small and have very little protein, they are not a priority pollen for bees to gather to feed their brood. However, many times corn pollen shed is during a general time of pollen dearth; on these occasions honey bees and bumble bees will vigorously gather corn pollen.

In the process of gathering, they will shake loose quite a bit also – and this can fall on adjacent plant silks. So, while corn is basically a wind pollinated plant, bees can be significant in pollination, particularly if there is no wind.

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