Ohio State University Extension
Department of Horticulture and Crop Science
2021 Coffey Road, Columbus, Ohio 43210-1044
Corn Pollination - An Overview
Unlike all other major grain crops, the corn plant has separate
male and female flowering parts. The tassel and ear shoot are the
male and female flowering structures, respectively, of the plant.
The flowering stage in corn, which involves pollen shed and
silking, is the most critical period in the development of a corn
plant from the standpoint of grain yield determination. Drought,
high temperature stress, as well as hail damage and insect
feeding have the greatest impact on yield potential during the
reproductive stage. The following is an overview of some of the
key steps and phases of the corn pollination process.
- Pollen shed usually begins two to three days prior to silk
emergence and continues for five to eight days with peak shed on
the third day. On a typical midsummer day, the shedding of pollen
is in the morning between 9:00 and 11:00 a.m.
- The tassel is usually fully emerged and stretched out before
any pollen is shed. Pollen shed begins at the middle of the
central spike of the tassel and spreads out later over the whole
tassel with the lower branches last to shed pollen.
- Pollen grains are borne in anthers, each of which contains a
large number of pollen grains. The anthers open and the pollen
grains pour out in early to mid morning after dew has dried off
the tassels. Pollen is light and is often carried considerable
distances by the wind. However, most of it settles within 20 to
- Pollen shed is not a continuous process. It stops when the
tassel is too wet or too dry and begins again when temperature
conditions are favorable. Pollen stands little chance of being
washed off the silks during a rain storm as little to none is
shed when the tassel is wet. Also, silks are covered with fine,
sticky hairs which serve to catch and anchor pollen grains.
- Under favorable conditions, pollen grain remains viable for
only 18 to 24 hours. However, the pollen grain starts growth of
the pollen tube down the silk channel within minutes of coming in
contact with a silk and the pollen tube grows the length of the
silk and enters the female flower (ovule) in 12 to 28 hours.
- A well developed ear shoot should have 750 to 1,000 ovules
(potential kernels) each producing a silk. The silks from near
the base of the ear emerge first and those from the tip appear
last. Under good conditions, all silks will emerge and be ready
for pollination within 3 to 5 days and this usually provides
adequate time for all silks to be pollinated before pollen shed
- Pollen of a given plant rarely fertilizes the silks of the
same plant. Under field conditions 97% or more of the kernels
produced by each plant are pollinated by other plants in the
- The amount of pollen is rarely a cause of poor kernel set.
Each tassel contains from 2 to 5 million pollen grains which
translates to 2,000 to 5,000 pollen grains produced for each silk
of the ear shoot. Shortages of pollen are usually only a problem
under conditions of extreme heat and drought. Poor seed set is
more often associated with poor timing of pollen shed with silk
emergence (silks emerging after pollen shed).
Source: Aldrich, S. R., W. O. Scott, and R. G. Hoeft. 1986.
Modern Corn Production. 3rd edition. A&L Publications (Chapter 1
- "How the Corn Plant Grows").
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Keith L. Smith, Associate Vice President for Ag. Adm. and
Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-6181
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