Corn

Zea mays

Corn, or maize (Zea mays), is a tall grass that was domesticated from a wild grass called teosinte in southern Mexico about 9,000 years ago. Each plant carries male flowers in a tassel at the top and female flowers on ears lower down, where every silk can turn into one kernel. Today maize is the most produced grain crop on Earth, grown for food, animal feed and fuel.

Also known as Maize

Corn plant powers

2–25 million pollen grains per tassel
Corn is pollinated by the wind. Each morning the tassel shakes out clouds of pollen that drift onto the silks of nearby plants.
- All the pollen in one anther can be released in as little as 3 minutes.
- In a 24 km/h (15 mph) wind, pollen grains can travel as far as 0.8 km in the couple of minutes they stay alive.
- Most pollen is shed in the morning, when it is cooler. Extreme heat of about 38 °C (100 °F) or more can kill pollen.
- Flowers on the tassel open in a careful order: the upper flower of each pair usually sheds first, the lower one later that day or the next.
Sources [1]
3.8 cm of silk growth a day, at first
Long sticky silks grow out of the husk to catch pollen. Each silk is a tube that leads to one kernel-to-be, so every kernel on a cob had its own silk.
- Silks start to grow 10–14 days before they appear, beginning with the ovules at the base of the cob.
- When they first poke out of the husk, silks can grow up to 3.8 cm (1.5 inches) a day.
- All the silks on an ear usually come out within 4–8 days.
- If a silk catches no pollen, it stops growing about 10 days after it appears, and its kernel never forms.
Sources [2]
400–600 kernels that make it to harvest
Weeks before it flowers, the plant is already building its ear: first it sets the number of rows, then the number of kernels in each row.
- The number of rows is decided early, when the plant has about 5 to 7 leaves.
- Kernels-to-be are added to each row until the plant has 12 to 15 leaves.
- An ear forms up to about 1,000 ovules, but only around 400 to 600 kernels usually survive to harvest.
- Hail, frost, flooding or sudden heat while the ear is forming can mean fewer kernels later.
Kernels on one ear
Kernels at harvest400–600
Kernels-to-be (ovules)750–1,000
Hybrids grown in Indiana, USA
Sources [2, 3]
always even number of kernel rows
Count the rows on a cob and you will almost always get an even number. Rows begin as single ridges that split into pairs.
- Most ears have 14 to 18 rows; the range is about 12 to 22.
- Each row starts as one ridge of cells that divides into two, so rows come in pairs.
- Only severe stress while the ear is forming, like a sudden frost, hail or flooding, can break the pattern.
Sources [2, 3]
more rings in the soil = less bending
Rings of thick roots grow out of the lower stalk and push into the ground like tent pegs, helping the tall plant stand up to wind.
- Brace roots grow from stem nodes above the soil. Some stay in the air; others grow into the ground.
- In field tests, scientists pushed plants and then cut away one ring (whorl) of brace roots at a time: the stalks bent more each time a ring touching the soil was removed.
- Not every ring helps equally, and how brace roots develop is still being worked out.
Sources [11, 12]
45+ times C4 evolved in plants
Corn’s leaves pump carbon dioxide into special cells around their veins. This C4 trick keeps photosynthesis efficient on hot, bright days.
- In most plants (C3 plants), heat makes the sugar-making enzyme, Rubisco, less efficient, and energy is lost to photorespiration.
- C4 plants concentrate carbon dioxide around Rubisco in bundle-sheath cells, so this happens far less.
- C4 photosynthesis evolved more than 45 separate times, in 19 plant families. It first appeared in grasses about 24–35 million years ago.
- Wheat and rice are C3 crops. Since 2008 a group of scientists has been trying to give rice the C4 system.
Sources [6, 7, 8, 13]
29–82% of nitrogen from the air (one landrace)Still debated
A tall local maize from the Sierra Mixe mountains in Mexico grows slimy aerial roots. Bacteria living in the slime turn nitrogen from the air into food for the plant.
- The Sierra Mixe varieties grow over 5 m tall, with rings of aerial roots at every node that ooze a sugary gel.
- Five years of field tests found that 29–82% of the plants’ nitrogen came from the air.
- Beans and other legumes are famous for this; it was not expected in a cereal like maize.
- This was only shown in 2018 in one landrace, so scientists are still studying how it works and whether other corn can use it.
Sources [10]
180 °C when almost all popcorn pops
A popcorn kernel is a tiny pressure cooker. Water inside turns to steam, the hard hull holds it in, and then the kernel bursts and the starch puffs out.
- Popcorn needs about 13.5–14% water inside to pop.
- Water turns to steam at 100 °C, but the hull holds until the kernel reaches about 180 °C.
- The burst takes a few hundredths of a second. A ‘leg’ of starch pushes on the pan and makes the popcorn jump.
- The ‘pop’ sound seems to come from the water vapour rushing out.
How hot?
Popcorn pops≈180 °C
Water boils100 °C
Sources [4, 14]

Tap a pin on the model or a part below.

≈6,000 pollen sacs (anthers) on one tassel
- The tassel at the top of the plant is a bunch of male flowers.
- About 1,000 tiny flower clusters (spikelets) form on each tassel, each with two flowers inside.
- That adds up to roughly 6,000 anthers, the little sacs that hold the pollen.
- The plant reaches its full height at about the time the tassel comes out.
Sources [1]
2–25 million pollen grains from one tassel
- The yellow or white dust that falls from a tassel is millions of nearly microscopic pollen grains.
- Estimates range from 2 to 25 million grains per tassel; they are hard to count.
- Pollen shed usually peaks in mid-morning, once the dew has dried.
- Once in the air, a pollen grain stays alive for only a few minutes before it dries out.
Sources [1]
1 silk for every kernel
- Each silk is joined to one ovule, a kernel-to-be.
- A silk has to catch a pollen grain for its ovule to be fertilised and become a kernel.
- Silks from the base of the ear grow first; the ones near the tip come out last.
- Silks can catch pollen for up to 10 days, but most kernels are fertilised in the first 4–5 days.
Sources [2]
750–1,000 possible kernels (ovules) per ear
- The ear is the plant’s female flower head, wrapped in leafy husks.
- In hybrids grown in Indiana, an ear forms about 750 to 1,000 ovules: about 50 to 60 in each row.
- Only about 400 to 600 kernels usually survive to harvest.
- The ear starts forming when the plant is about knee-high, and its size is set 10–14 days before the silks appear.
Sources [2, 3]
14–18 rows on most ears (12–22 possible)
- A kernel has three main parts: the germ (the baby plant), the starchy endosperm and the hull, called the pericarp.
- Kernel rows start as single ridges of cells that split into pairs, so ears almost always have an even number of rows.
- Once the number of rows is set, no more rows can form.
- Sweet corn kernels taste sweet because of a gene called sugary1: changes in it mean more sugar and less of one kind of starch.
Sources [3, 4, 5]
C4 type of photosynthesis
- Corn leaves use C4 photosynthesis, a set of changes in leaf structure and chemistry that packs carbon dioxide around the enzyme that turns it into sugar.
- This makes photosynthesis more efficient in heat and bright light, where ordinary (C3) plants lose a lot of energy to a process called photorespiration.
- C4 photosynthesis first appeared in grasses about 24–35 million years ago.
- Rice does not have it: scientists are trying to add the C4 system to rice to raise yields.
Sources [6, 7, 8]
over 5 m tall: Sierra Mixe maize in Mexico
- Corn grows one strong main stalk. Its wild ancestor, teosinte, is much bushier, with many side branches.
- A gene called teosinte branched1 (tb1) is a big part of that difference.
- Local varieties grown in the Sierra Mixe mountains of Oaxaca, Mexico, grow to over 5 m tall.
Sources [9, 10]
more whorls in the soil = a steadier stalk
- Brace roots (prop roots) grow out of the stem nodes above the ground, in rings called whorls.
- Some stay in the air; others reach down and grow into the soil.
- Tests in the field showed that the more whorls touch the soil, the better they anchor the stalk.
- Scientists only recently proved that brace roots really brace the plant, and many questions about them are still open.
Sources [11, 12]
- Roots take up water and minerals from the soil, and pipe-like tissue called xylem carries them up the stalk.
- Brace roots that reach the ground may help with taking up water and nutrients as well as with anchorage.
- In one Mexican landrace, slimy aerial roots host bacteria that take nitrogen from the air.
Sources [10]

Real corn

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

Sweet cornTall green plant with a pale tassel, green husks and yellow kernels.Sweet because of changes in the sugary1 gene: more sugar, less of one kind of starchTassels: the male flowers that make the pollen. Photo: Knowledge and philosophy, CC BY-SA 4.0
Silks: each one leads to a single kernelPhoto: Jeffery Martin, CC0
Brace roots anchoring a maize plantPhoto: Thanduanlung Kamei, CC BY-SA 4.0
Sweet cornTall green plant with a pale tassel, green husks and yellow kernels.Sweet because of changes in the sugary1 gene: more sugar, less of one kind of starchA young cornfield in Pennsylvania, USA. Photo: Derek Ramsey (Ram-Man), GFDL 1.2
Flint cornMulticoloured kernels in reds, blues, purples, yellows and whites, sometimes all on one cob.Local varieties (landraces) hold much of maize’s genetic diversityMulticoloured Glass Gem corn. Photo: timlewisnm, CC BY-SA 2.0
Flint cornMulticoloured kernels in reds, blues, purples, yellows and whites, sometimes all on one cob.Local varieties (landraces) hold much of maize’s genetic diversityBlue maize kernels from Mexico. Photo: Jmsinuhe, CC BY-SA 3.0
PopcornSmall ears packed with small, shiny kernels.Its hull has just the right thickness to hold steam until the kernel burstsAn ear of popcorn grown in a garden. Photo: Geo Lightspeed7, CC BY-SA 4.0
Teosinte (wild ancestor)A bushy wild grass with many branches and tiny ears; each seed sits in a hard, stony case.Two gene changes (tb1 and tga1) helped turn it into maizeTeosinte, corn’s wild relative, in Oaxaca, Mexico. Photo: Bernardo Bolaños, CC BY-SA 3.0

Corn by the numbers

Measured by scientists and agencies, with comparisons you can picture.

World harvest: 1.22 billion t; of maize in 2024, more than wheat or rice⁠[20, 21]; Maize1,218 million tWheat798 million t
Pollen per tassel: 2–25 million; grains, alive for only a few minutes in the air⁠[1]
Kernels-to-be: 750–1,000; ovules on one ear; 400–600 kernels usually survive⁠[3, 2]
Kernel rows: 14–18; on most ears, and almost always an even number⁠[3]
Silk growth: 3.8 cm/day; for the first day or two after silks appear⁠[2]
Domesticated: ≈9,000 years ago; in southern Mexico, from teosinte⁠[15]
Oldest evidence: 8,700 years; maize starch grains from a rock shelter in Mexico’s Balsas valley⁠[17]
Genes: 32,000+; in a 2.3-billion-letter genome, nearly 85% of it jumping genes⁠[22]
Popping point: 180 °C; with 13.5–14% water inside the kernel⁠[14, 4]
Tall landrace: over 5 m; Sierra Mixe maize from Oaxaca, Mexico⁠[10]

Corn myths and facts

Old sayings and kitchen science, checked against the evidence.

0 of 8 answered

“Every strand of corn silk leads to one kernel.”
“An ear of corn always has an even number of rows.”
“Corn should be ‘knee high by the Fourth of July’.”
“Corn pollen floats around alive for hours.”
“Popcorn pops as soon as the water inside boils.”
“Corn is a kind of grass.”
“Corn came from a wild grass that looks nothing like it.”
“Corn’s single tall stalk is partly down to one gene.”

Corn records

Superlatives with numbers behind them.

Most produced grain
1.22 billion t
Maize
harvested worldwide in 2024, ahead of rice (820 million t) and wheat (798 million t). Together the three make up about 91% of all cereals.⁠[20, 24, 21, 25]
Biggest grower
378 million t
United States
of maize in 2024, followed by China (295 million t) and Brazil (115 million t).⁠[20]
Oldest maize traces (2009 study)
8,700 years
Xihuatoxtla shelter, Mexico
Starch grains and tiny silica bodies from maize in the Central Balsas valley, where its wild ancestor grows.⁠[17]
Early cobs and tassels
6,700–3,000 years
Paredones and Huaca Prieta, Peru
Some of the earliest known maize cobs, husks, stalks and tassels, from coastal Peru.⁠[16]
Jumping-gene genome
≈85%
Maize
of its 2.3-billion-letter genome is made of transposable elements, or ‘jumping genes’. Barbara McClintock won the 1983 Nobel Prize for discovering mobile genetic elements.⁠[22, 26]

Corn’s growing season

From a few leaves to a full cob in one summer. Farmers name the stages by counting leaves (V) and by flowering stages (R).

5–7 leaves
The ear begins
When the plant is about knee-high, the top ear starts to form and quickly sets its number of kernel rows.⁠[3]
12–15 leaves
Ear size set
The plant finishes adding kernels-to-be to each row, and the silks start to grow inside the husk, 10–14 days before they appear.⁠[3, 2]
Tassel out (VT)
Full height
The last branch of the tassel comes out of the leaves. The stalk stops growing taller at about this time.⁠[1]
Silking (R1)
Silks appear
Silks poke out of the husk and grow up to 3.8 cm a day. All of them appear within 4–8 days.⁠[2]
Mid-morning
Pollen time
Pollen shed peaks once the dew dries. In Indiana, fields flower between late June and late July.⁠[1]
First 4–5 days
Kernels start
Most silks are fertilised in the first few days. Silks that catch no pollen stop growing about 10 days after they appear.⁠[2]
Harvest
A full cob
Of up to 1,000 ovules, usually 400 to 600 become kernels on the finished ear.⁠[2]

How teosinte became Corn

Maize is one of the great inventions of Indigenous farmers in the Americas.

≈9,000 years ago
One domestication
DNA from 264 plants shows that all maize came from a single domestication of teosinte in southern Mexico.⁠[15]
8,700 years ago
Oldest traces
Maize starch grains and tiny silica bodies (phytoliths) are left in the Xihuatoxtla rock shelter in the Balsas valley, along with early squash.⁠[17]
Early farming
Key gene changes
A change in the tga1 gene freed the kernel from its stony case, and tb1 helped give the plant one main stalk.⁠[19, 9]
6,700–3,000 years ago
Down to Peru
Maize cobs, husks, stalks and tassels are left at Paredones and Huaca Prieta on the coast of Peru. Andean types are already appearing.⁠[16]
Over centuries
Across the Americas
From the Mexican highlands, maize spread along two main routes, and farmers bred an enormous range of local varieties.⁠[15]
Traditional farming
The Three Sisters
The Haudenosaunee (Iroquois) planted maize, beans and pumpkins together in the same field, a system called the Three Sisters.⁠[27]
1979
A new wild relative
Botanists describe Zea diploperennis, a perennial teosinte found only on Cerro de San Miguel in the Sierra de Manantlán, Jalisco.⁠[28]
1983
Nobel Prize
Barbara McClintock wins the Nobel Prize for discovering mobile genetic elements, or ‘jumping genes’.⁠[26]
2009
Genome read
Scientists publish the genome of the maize line B73: 2.3 billion letters and over 32,000 genes.⁠[22]
2018
Roots that fertilise
Sierra Mixe maize is shown to get up to 82% of its nitrogen from the air, with help from bacteria in root slime.⁠[10]

Corn vs wheat vs rice

The three giant grasses that feed the world.

Maize vs wheat vs rice
	Maize (corn)	Wheat	Rice
World harvest, 2024⁠[20, 21, 24]	1.22 billion t	798 million t	820 million t
Biggest grower, 2024⁠[20, 21, 24]	United States	China	India
Photosynthesis⁠[6, 13, 8, 7]	C4: efficient in heat	C3	C3 (scientists are trying to add C4)

Maize, wheat and rice made up 91% of the world’s cereal harvest in 2023.

Is Corn endangered?

Corn itself is not, but some of its wild relatives are, and the diversity of old local varieties matters for the future.

IUCN Red List

Least Concern (LC)

Trend unknown

The IUCN Red List lists Zea mays, which includes the wild teosinte subspecies, as Least Concern. The crop is grown on a huge scale: more than 1.2 billion tonnes a year.⁠[23, 29, 20]

IUCN Red List (via GBIF and Wikidata)

Threats

Rare wild relatives3
Three wild Zea species are on the Red List as threatened: Zea perennis (Critically Endangered), Zea diploperennis (Endangered) and Zea luxurians (Vulnerable).⁠[30, 31, 32]
Tiny ranges
Zea diploperennis was found only on one mountain, Cerro de San Miguel in Jalisco, Mexico, when it was described in 1979.⁠[28]

What’s helping

Farmers’ own varieties
Indigenous and local farmers created maize’s extraordinary diversity and still grow landraces such as the Sierra Mixe maize, which carries traits no one knew about until 2018.⁠[15, 10]
Knowing the genes
Reading the maize genome and finding genes like tb1 and tga1 shows which traits came from teosinte, and why wild relatives are worth keeping.⁠[22, 9, 19]

Wild relatives

Zea perennisCritically Endangered
A perennial teosinte: it lives for several years instead of one season.⁠[30]
Zea diploperennisEndangered
Perennial teosinte of the Sierra de Manantlán, Jalisco; its seeds are eaten locally.⁠[31, 28]
Zea luxuriansVulnerable
A wild teosinte species.⁠[32]

Corn quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What is the tassel at the top of a corn plant?

Corn field notes

Diet, food web, safety and badges from the Snappit field guide.

Ecological connections

HumanEats it
Cultivated globally as a major food source.
Western corn rootwormPest
Larvae feed on corn roots, damaging the plant.
Fall armywormPest
Larvae chew on corn leaves and bore into ears.
American CrowEats it
Often feeds on corn kernels in fields.

Safety

Danger 1/5 · Very low

Explore with care and ask an adult if you’re unsure what to do.

Traits

Collections

Classification

Kingdom: Plantae
Phylum: Tracheophyta
Class: Liliopsida
Order: Poales
Family: Poaceae
Genus: Zea

Sources for these corn facts

32 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Corn?

Compare seed heads, stem shape, how leaves attach, and the joint where leaf meets stem. A patch of mown lawn rarely shows enough for an exact ID. Grass Identifier: upload a photo and compare the visible details.

How tall is Corn?

150-300 cm

How wide does Corn spread?

30-60 cm

When does Corn bloom?

Summer

Is Corn edible?

Yes

Is Corn toxic?

None

What is Corn's lifecycle?

Annual

How is Corn pollinated?

Wind

What are corn silks for?

Silks catch pollen. Each silk is attached to one ovule on the cob; when a pollen grain lands on it, the ovule can be fertilised and grow into a kernel.

Do ears of corn always have an even number of rows?

Almost always. Rows begin as single ridges that divide into pairs, so most ears have an even number, usually 14 to 18. Severe stress while the ear forms can break the pattern.

How many kernels are on an ear of corn?

An ear forms about 750 to 1,000 kernels-to-be, but usually 400 to 600 kernels survive to harvest, depending on the variety and the growing season.

Where did corn come from?

Corn was domesticated from a wild grass called teosinte in southern Mexico about 9,000 years ago. The oldest traces, 8,700 years old, come from the Balsas River valley.

Why does popcorn pop?

Each kernel holds about 13.5–14% water inside a hard hull. When heated, the water turns to steam, the pressure builds and at about 180 °C the hull bursts and the starch puffs out.

What is the difference between corn and maize?

They are two names for the same plant, Zea mays. In this card we use both.

Is corn endangered?

No. The IUCN Red List lists Zea mays as Least Concern, and over a billion tonnes are grown every year. Some of its wild relatives, such as Zea perennis and Zea diploperennis, are threatened.

What are the roots at the bottom of a corn stalk?

They are brace roots, which grow from the stem above the ground. The ones that reach the soil help anchor the tall plant against wind.