Corn (Zea mays L.)

Common Name: Corn

Scientific Name: Zea mays L.

Synonym: Zea mays var. parviglumis H. H. Iltis & Doebley, Zea mays L. subsp. Mays, Zea curagua Molina, Zea indentata Sturtev., Zea indurata Sturtev., Zea japonica Van Houtte, Zea mays cv. alba Alef., Zea mays cv. leucodon Alef., Zea mays var. flavorubra K?rn., Zea mays var. indentata (Sturtev.) L. H. Bailey, Zea mays var. indurata (Sturtev.) L. H. Bailey, Zea mays var. japonica (Van Houtte) A. W. Wood, Zea mays var. saccharata (Sturtev.) L. H. Bailey, Zea mays var. tunicata Larra?aga ex A. St.-Hil., Zea mays var. vulgata K?rn. & H. Werner, Zea saccharata Sturtev.

Family: Poaceae

Tribe: Andropogoneae

Origin: Mesoamerica.

Time of introduction:


Corn is an annual grass. It is a very important row crop in North America, and is grown in nearly every state, although its major production area is in the North Central states. Culms grow 23 to 31 inches (60-80 cm) high, straight, with internodes cylindrical in the upper part, and alternately grooved on the lower part with a bud in the groove. Corn has leaf blades that are long, wide, and tapered, and a dense, fibrous root sytem. It is adapted to well-drained, medium-textured soils and does not tolerate drought or flooding. As forage, corn is used mainly as a silage crop. It is subject to many diseases, but they have been overcome by chemical seed treatment or by breeding resistant varieties.

Life cycle (annual/biennial/perennial):

Growth habit & Regrowth type:
Upright growth habit. Single upright stem with solid internodes.

Invasive potential:
Corn appears as a volunteer in some fields and roadsides, but it never has been able to establish itself outside of cultivation. Some of the other species of Zea are successful wild plants, but have no pronounced weedy tendencies.



Image Gallery: The OSU Forage Information System contains an Image Gallery that includes Corn photographs and drawings useful in identification. The URL for the gallery is:

The direct URL for Corn is:

Inflorescence: The male inflorescence (tassel), which occurs at the stem apex, is a panicle with paired spikelets containing paired florets. The female inflorescence (ear) is a thick spike with pairs of spikelets and is generally located six to seven nodes below the apex.

Spikelets: On the male inflorescence, spikelets contain paired florets. For the female inflorescence, the spike has pairs of spikelets occuring in several rows.


Stem: Culms grow 23 to 31 inches (60-80 cm) high, straight, internodes cylindrical in the upper part, alternately grooved on the lower part with a bud in the groove. The stem is filled with pith.

Leaf: Leaf blades are long, wide, and tapered. The leaf sheath overlaps the stem. The ligule is membranous and blunt or is absent in some hybrids.


Root: Corn produces a dense, fibrous, adventitious root system and forms aerial (brace) roots at nodes near the soil surface.

Physiology and growth period:
Corn is an annual, warm season grass. Growth initiates at ____F(___C) and stops at ___F(___C). Peak germination is at 68 to 86 F (20-30 C) and growth at 64 to 69 F (18-21 C).

Self-pollination and fertilization and cross- pollination and fertilization are usually possible and frequencies of each are usually determined by physical proximity and other physical influences on pollen transfer. A number of complicating factors, such as genetic sterility factors and differential growth rates of pollen tubes may also influence the frequencies of self- fertilization versus cross-fertilization.

Quality/anti-quality factors:



Corn is planted on more land than any other US crop. It is adapted to well-drained, fertile, medium-textured soils and does not tolerate flooding. An annual rainfall of more than 20 inches (500 mm) is needed, with best yields usually in the 47 to 50 inches (1,200-1,500 mm) area.

Suitability zones:
Corn is grown in almost every state in the US, but its major production region is in the North Central states. It has a wide range, from 58 degrees N in Canada to 40 degrees S.



Quantitiative Table:

Max Temp (C)
Min Temp (C)
Precip (mm)
Soil pH Soil Drainage
Soil Salinity
Low High Low High Low High Low High Low High Low High
Well Adapted
1. For the High values for January Minimum temperature and Annual Precipitation: "9999 is entered to indicate no limit to the high values for this tolerance category."
2. For Soil Drainage categories, " Abbreviations are used for Soil Drainage categories: VPD (very poorly drained), PD (poorly drained), SPD (somewhat poorly drained), MWD (moderately well drained), WD (well drained), SED (somewhat excessively drained), ED (excessively drained)."

Climate: An annual rainfall of more than 20 inches (500 mm) is needed, with best yields usually in the 47 to 50 inches (1,200-1,500 mm) area; it is often an irrigated crop. Kitale experiments show that the more rainfall after five weeks' growth, the higher the yield. It is fairly drought tolerant up to five weeks, but thereafter is very susceptible. Dry weather at pollination time seriously affects pollination and hence yields. Corn is very susceptible to frosts.

Soils: Corn is adapted to well-drained, fertile, medium-textured soils and does not tolerate flooding. Alluvial loams, deep latosols and clay loams are preferred. It requires high fertility and moisture availability. Maize gave maximum yields at ECe of 2 mmhos/cm, 50 percent at ECe 9 mmhos/cm and nil at 15.3 mmhos/cm. Further studies showed that in water cultures, or on mineral soils with surface irrigation and continuous leaching, the maximum salt concentration in the soil saturation extract that does not reduce maize yields is about 1 100 mg/l total dissolved salts (ECe - 1.7 dS/m). The maximum permissible salt concentration of irrigation water to sustain maize production is about 300 mg/l, an ECW of 0.45 dS/m.

Grazing Management: Corn is not generally grazed, but sometimes it can be used as an emergency pasture.

Turf Management: Corn is not used as a turf species.

Pests: Diseases: Maize is subject to many diseases, chief of which are maize smut (Ustilago maydis), head smut (Sphacelotheca reiliana), and various stalk and ear rots such as Gibberella and Diplodia. They have been overcome by chemical seed treatment or by breeding resistant varieties.

Pests: Insects: A variety of pests are encountered. Chinch bug (Blissus leucopterus) is a major pest in the United States. The corn ear worm (Heliothis armigera) is a problem in Australia.

Pests: Nematodes: Common pests on corn are The Sting Nematode, Ring nematodes, Spiral Nematodes, The Corn Cyst Nematode, The Lance Nematode, The Dagger Nematode, The Needle Nematode, The Root-Knot Nematodes, The Lesion Nematode, Stubby-Root Nematodes, and Stunt Nematodes.

For more information on these nematodes, see the University of Nebraska-Lincoln, Corn Nematodes Website.


Numerous cultivars are available throughout the world and contact should be made with local extension officers to ascertain what is the current preference to specific conditions. Most countries have bred their own cultivars to suit their varying conditions. Dent maize (Zea mays indentata) is the main variety grown commercially for grain and fodder, but there are other types such as pod corn (Zea mays tunicata), a curiosity; flour corn (Zea mays amylacea) for human consumption; flint corn (Zea mays indurata), preferred for the European market, with horny endosperm; sweet corn (Zea mays saccharata), used as a vegetable; pop corn (Zea mays everta), used as a snack food. High-lysine corn has been improved for human nutrition. Open pollinated varieties have been used for a long time but now most of the commercial dent maize is either a single cross or a double cross hybrid bred for special areas, soils and climatic conditions.


Corn is usually planted in the spring when soil temperatures exceed 50 F (10 C). Seeding is usually done in rows spaced 15 to 40 inches (38-101 cm) apart. A deep (7.8 in; 20 cm) friable seed-bed should be prepared, as maize is comparatively shallow rooted and needs loose soil in which the roots can forage. It is usually drilled in rows for grain and fodder, though it can be broadcast thickly for turning in as a green manure.

Seeding rate:
Corn is usually planted at populations between 25,000 and 30,000 plants/acre.

Seeding depth:
Sow at 2.9 to 3.9 inches (7.5-10 cm) depth and cover using a fined instrument, then compact with a following press wheel.

Fertilization and liming:
Corn grown for forage production requires more soil fertility than corn grown for grain. Greater nutrient removals are taken in forage production with stalk and leaf removal from the field. Fertility recommendations are continuously being fine-tuned for various soils, but yield responses are generally known and can be predicted. The decision to fertilize soil for corn forage production depends upon obtaining a soil test for the field. Corn generally requires a complete fertilizer, with heavy demands from about 40 days until maturity. Zinc deficiency causes leaf chlorosis and can easily be overcome by the use of zinc sulphate.


Maize is a major human food grain in Africa and in eastern Indonesia. Some 85 percent of the maize crop in the United States is fed to livestock as grain and silage.

Seed crop:

As forage, corn is used primarily as a silage crop but sometimes is used as an emergency pasture. Corn crop residues are often used as roughage for gestating beef cows. It makes probably the best silage of the grass family, with heavy yields and high acceptability and without the need for additives. It is cut when the grain is full and glazed, in the medium dough stage.

Erosion Control/Conservation:
Not used for erosion control. As maize is usually a row crop and has a poorly developed root system, crops are very susceptible to erosion.

Wildlife habitat and feed:

Corn is not used as a turf species.

Economic value:



Soil and water conservation:

Corn is not used as a turf species.


  1. Animal & Plant Health Inspection Service (APHIS): Biotechnology Regulatory Services. Corn webpage [Online]. USDA. Available at (verified 26 July 2004).
  2. Barnes, R.F., M.E. Heath, D.S. Metcalfe. 1973. Forages: The Science of Grasslands Agriculture, Third Edition. Iowa State University Press. Ames, IA. 41:439-440.
  3. Barnes, R.F., M. Collins, K.J. Moore, C.J. Nelson. 2003. Forages: An Introduction to Grassland Agriculture. Iowa State Press. Ames, Iowa.
  4. FAO Grassland Index [Online]. Zea mays L. Available at (verified 23 July 2004).
  5. Jacques, D. 2002. The identification of certain native and naturalized grasses by their vegetative characters. Canadian Agriculture Library (CAL) [Online]. Available at (verified 12 July 2004).
  6. Lauer, J. 2003. Keys to Higher Corn Forage Yields. University of Wisconsin. Madison, WI. Available at (verfied 23 July 2004).
  7. USDA, NRCS. 2004. The PLANTS Database, Version 3.5 [Online]. National Plant Data Center, Baton Rouge, LA. Available at (verified 12 July 2004).

David B. Hannaway and Christina Larson, Oregon State University

Document creation:
4 June 2004

Last update:
26 July 2004


Review date: