Gossypium hirsutum, or Gossypium mexicanum, is an annual sub-shrub, up to 1.5 meter tall. In warm climates, it is biennial or perennial. Cotton is grown in the United States mostly in areas from Virginia southward and westward to California, in an area often referred to as the Cotton Belt. Four species of the genus Gossypium are known as cotton, which is grown primarily for the seed hairs that are made into textiles.
There is 6-8 flowers on each fertile branch. The white to yellowish flowers are up to 3.5 inches across. After flowering in mid-Summer, water is restricted and fertilizer is withheld until the bolls split and the cotton is harvested. Gossypium hirsutum is generally self-pollinating. Cotton blooms in the Summer when grown outside, but when grown in the greenhouse plants can bloom at any time of the year.
The flowers are followed by 1.5 inch long spherical fruits, smooth and light green. Fruits are 3-5 celled with 5-11 seeds per cell. There are branches of two kinds, vegetative and fruiting. It has cordate leaves that are 3-5 lobed reaching up to 6 inches across.
Planting to flowering is 80-110 days with another 55-80 days until the boll opens. Hand-harvesting still accounts for the largest percentage of harvest in spite of advances in mechanization. Hand methods provide a higher grade of cotton and gets more from the fields.
Hardiness zones 9-11, (-5øC/25øF, 4øC/40øF) in Winter. Sensitive in any stage to frost, Cotton limits are set by the early and late frosts. Cotton requires a minimum of 180-200 frost-free days of uniformly high temperatures, averaging 21-22øC. Full sunlight is critical for proper development. Moderate rainfall is preferable during vegetative growth followed by a dry period to allow the bolls to mature and be picked.
Cotton is tolerant of a wide variety of soils, but thrives best on deep, friable, moisture-holding soils with good humus supply. Optimum pH is 6.1-6.5. Use a soil mix consisting of equal parts of loam and sand. Allow the plants to dry slightly in between waterings and fertilized monthly during the growing and flowering season.