The Structure of the Cotton Plant

Cotton fibers are valued for their use in fabrics.

Humans have cultivated cotton plants for their fibers for thousands of years. Today, cotton is one of the most important row crops in the United States. The structure and development pattern of this plant are crucial to farming it successfully.

Types

According to Purdue University, most commercial cotton comes from Gossypium hirsutum, one of four species in the same genus that are collectively called cotton. These plants are shrubs that can grow up to 5 feet (1.5 meters) in height.

Stems and Leaves

The stem features a number of nodes where secondary stems branch off the main stem. The first few nodes may give rise to vegetative stems, while the fruiting stems begin at the fourth through seventh nodes -- depending on the plant. Vegetative stems are similar to the main stem in their structure; starting at the fifth or sixth node, vegetative stems generally give rise to fruiting stems. Unlike the vegetative stems, the fruiting stems grow the flowers that will yield the actual cotton. Leaves are usually about 4 to 6 inches (10 to 15 centimeters) wide with three to five lobes on each leaf.

Flowers and Fruit

Flower buds on cotton plants are called squares. Each square grows for three weeks or so before it blooms. Flowers contain both male and female reproductive structures; the flower petals turn pink on the second day after they open and are shed shortly thereafter. Once a flower has been pollinated, the fruit or boll begins to develop. The boll contains the white fibers so prized by human cultivators. The bolls are pale-green and ball-shaped early during their development and take 45 days or so to mature.

References

• Australian Department of Health and Aging: The Biology and Ecology of Cotton (Gossypium hirsutum) in Australia
• Purdue University: Gossypium Hirsutum
• University of Missouri Extension: Cotton Plant Development and Plant Mapping