Zea mays

Photo Credit: Howard F. Schwartz, Colorado State University, Bugwood.org. Creative Commons Attribution 3.0 License, http://creativecommons.org/licenses/by/3.0/us/.
Zea mays
Common Name: corn
Plant Functional Group: Graminoid
Class > Order > Family: Magnoliopsida > Poales > Poaceae
Where is the species found?
States & Provinces
AL, AR, AZ, CA, CO, CT, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NE, NH, NJ, NM, NV, NY, OH, ON, OR, PA, PR, QC, RI, SC, TN, TX, UT, VA, VI, VT, WA, WI, WV, WY
Which phenophases should I observe?
Do you see...?
Leaves Initial growth
New growth of the plant is visible after a period of no growth (winter or drought), either as new green shoots sprouting from nodes on existing stems, new green shoots breaking through the soil surface, or re-greening of dried stems or leaves. For each shoot, growth is considered "initial" until the first leaf has unfolded or has fully re-greened.
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Leaves
One or more live, green, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once it unrolls slightly from around the stem and begins to fall away at an angle from the stem. Do not include fully dried or dead leaves.
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What percentage of the plant is green?

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Flowers Flower heads
One or more fresh flower heads (inflorescences) are visible on the plant. Flower heads, which include many small flowers arranged in spikelets, emerge from inside the stem and gradually grow taller. Include flower heads with unopened or open flowers, but do not include heads whose flowers have all wilted or dried or begun to develop into fruits (grains). For Zea mays, the male inflorescence is the "tassel" which is initially compact, but eventually elongates and becomes plume-like and waves loosely at the top of the plant. The female inflorescence is the "ear" which includes the long, leafy bracts (the "husk") that cover and hide the flowers lined up in rows on the "cob". The stigmas of each individual flower grow long and extend out at the top of the husk (the "silk"). Once the female flowers are fertilized, the "ear" grows in size as the fruits develop.
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How many fresh flower heads are present?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
Open flowers
One or more open, fresh flowers are visible on the plant. A flower is considered "open" when reproductive parts (male anthers or female stigmata) can be seen protruding from the spikelet. Do not include flowers with wilted or dried reproductive parts. For Zea mays, the male flowers will open once the initially compact plume has elongated and is waving loosely. Female flowers are open when the stigmas are visible, that is, the first "silk" emerges from the top of the "husk".
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What percentage of all fresh flowers (unopened plus open) on the plant are open?

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Pollen release
One or more flowers on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface.
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How much pollen is released?

  • Little: Only a few grains are released.
  • Some: Many grains are released.
  • Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows

Fruits Fruits
One or more fruits are visible on the plant. For Zea mays, the fruit is a small grain ("kernel"), tightly arranged in rows that surround a thick cylindrical stem (the "cob") and are hidden under large, long bracts (the "husk"), and changes color from white or cream to its appropriate ripened varietal color (which may be yellow, red, purple, or blue) and in texture from soft or watery to firm or hard, depending on its appropriate ripened varietal characteristics.
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How many fruits are present?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
Ripe fruits
One or more ripe fruits are visible on the plant. For Zea mays, a fruit is considered ripe when the grain has matured to its appropriate ripened varietal characteristics.
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What percentage of all fruits (unripe plus ripe) on the plant are ripe?

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Recent fruit or seed drop
One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant.
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How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • More than 1,000
What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.

ITIS information for corn (ITIS TSN: 42269 )
USDA PLANTS profile for corn (USDA Symbol: ZEMA )