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Zea mays

Corn

Poaceae

Southwestern Mexico, Balsas River valley

Native to North America

SunFull Sun

WaterMedium

Overview

Zea mays is an annual grass grown as a warm-season crop, forming a single unbranched stem 4-10 feet (1.2-3 m) tall topped by a terminal tassel. Leaves are alternate and strap-shaped, 12-40 inches (30-100 cm) long and 2-5 inches (5-13 cm) wide, with a white midrib and finely toothed margins. The plant is monoecious: staminate flowers occur in the terminal tassel, while pistillate flowers form in lateral ears enclosed by husks, each silk being an elongated style. Pollination is by wind, so plants set full ears only when grown in blocks of four or more short rows rather than a single line. Ears mature 60-100 days after sowing depending on cultivar, carrying 300-800 kernels in 12-20 rows on a woody cob. The root system is shallow and fibrous, concentrated in the top 12-18 inches (30-45 cm), with prop roots arching from the lower nodes into the soil. Z. mays demands high nitrogen and steady moisture through tasseling and grain fill; a two-week drought at silking cuts kernel set sharply. Stems lodge in exposed sites after heavy rain once ears are filling, and sugar in sweet cultivars converts to starch within hours of harvest unless the ears are chilled.

Native Range

Zea mays was domesticated from teosinte, Zea mays ssp. parviglumis, in the Balsas River valley of southwestern Mexico roughly 9,000 years ago. No wild population of the domesticated form exists; it persists only in cultivation. It spread through the Americas before European contact and is now grown on every continent except Antarctica.

Suggested Uses

Grown in vegetable gardens and allotments as a summer crop, planted in blocks of four by four plants or larger at 10-12 inch (25-30 cm) spacing. The 6-8 foot (1.8-2.4 m) stems are used as a seasonal screen along garden boundaries and as living support in three-sisters plantings with beans and squash. Ornamental and popcorn cultivars are grown for dried ears used in autumn arrangements.

How to Identify

Recognised by a solid jointed stem 1-2 inches (2.5-5 cm) thick carrying alternate leaves in two ranks, topped by a feathery terminal tassel of paired spikelets. Ears form singly at leaf axils partway up the stem, each wrapped in overlapping husks with a tuft of silks 4-12 inches (10-30 cm) long emerging from the tip. Prop roots arch from the lowest two or three nodes into the soil, which separates Zea spp. from sorghum and sugarcane in the field.

Appearance

Size & Dimensions

Height4' - 10'

Width/Spread1'6" - 2'

Colors

Flower Colors

green

yellow

Foliage Colors

green

Bloom Information

Bloom Period

~2 weeks

Summer

Tassels emerge 50-70 days after sowing and shed pollen for 5-8 days, usually across July and August in temperate gardens. Silks appear 1-3 days after pollen shed begins, and each silk must receive a pollen grain to set a kernel. Flowering in most modern cultivars responds to accumulated heat rather than daylength, so sowing date largely sets the timing. Pollen viability falls above 95F (35C), producing gappy ears in hot dry seasons.

Detailed Descriptions

Flower Description

yellow-green tassels with yellow anthers; silks pale green ageing to red-brown

Foliage Description

medium green to blue-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.8 - 7.0(Neutral)

357912

Soil Types

loam sand silt

Drainagewell drained

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Grows in full sun with 6-8 hours of direct light and warm soil; germination is erratic below 55F (13C) and even at 60-70F (16-21C). Seed is sown 1-2 inches (2.5-5 cm) deep at 8-12 inches (20-30 cm) spacing in rows 30-36 inches (75-90 cm) apart, arranged in blocks of four or more rows for wind pollination. Deep loam at pH 5.8-7.0 with high organic matter suits the crop; nitrogen uptake peaks at knee height and again at tasseling, commonly met with 1-2 lb per 100 sq ft (0.5-1 kg per 9 sq m) of balanced feed split across those two stages. Water use runs 1-1.5 inches (25-40 mm) per week and rises during silking and grain fill. Corn earworm, Helicoverpa zea, enters through the silk channel and feeds on the ear tip, while common rust and northern corn leaf blight appear in humid summers. Feeder roots sit within 2 inches (5 cm) of the surface, so deep hoeing between rows severs them.

Pruning

No pruning is carried out on Zea mays. Tillers arising from the base are left in place; their removal has not been shown to raise ear yield and creates wounds that admit smut fungi. Spent stalks are cut at ground level after harvest and shredded or composted.