The kapok is truly the king of the jungle. Rising as an emergent tree, usually well above the canopy, the ceiba can grow to 240 feet (73 m) during its 500+ year lifespan.  Known by many names, ceiba, kapok, silk-tree, silk cotton tree, and world tree, it was sacred to the Mayans. Its distribution is global (tropical) both because of the nature of its seeds and because of its value as a cash crop.
The broad use of the name “ceiba” and “kapok” mean that it can lead to confusion. The genus “ceiba” has 18 different species in it, but the “pentandra” is the tree usually being referred to. 

Mayan Mythology
The Mayans knew it as Yax Che (“First Tree”). The kapok was the most sacred tree for the ancient Maya, and according to Maya mythology, it was the symbol of the universe. The tree signified a route of communication between the three levels of earth. Its roots reach down into the underworld, its trunk represented the middle world where the humans live, and its canopy of branches arched high in the sky symbolized the upper world and the thirteen levels in which the Maya heaven was divided.

Its Own Ecosystem
Over the many decades that a ceiba grows it has a complex network of interactions and symbiotic relationships supporting many dozens of other plant and fungal species, from the vines and orchards (bromeliads) and other epiphytes (air plants, without roots in the soil) that grow on its massive structure allowing them to get access to the sunlight that never makes it to the rainforest floor. Additionally, they host colonies of insects, frogs, snakes and birds that live in it and feed on it and its inhabitants. Colonies of ant sometimes inhabit a tree, living more than 100 feet above the forest floor, never leaving the safety of their towering home.  Pictures of ceiba, towering over the forest, with hundreds of vines and other plants growing on it are iconic rainforest images.
They thrive in a variety of warm climates (they are not freeze tolerant) from very wet rainforest to areas with pronounced wet-dry seasons. Ceiba are sensitive to drought, and are deciduous (shed their leaves) in dry periods, to protect themselves. The night blooming flowers are also means for water conservation (flowers give off a lot of water in the hot sun, and a tree with 4,000 flowers open to the hot tropical sun has to pull a lot of water up 200 feet to keep them moist).

Reproduction
A large ceiba can produce as much as 20 gallons of nectar per day, and its aromatic (and unpleasant) night-blooming flowers attract bats, bees and many other pollinators. When those flowers mature, a mature ceiba can produce as many as 4,000 fruit at the same time.  Each  dehiscent fruit (meaning it will split open) holds around 200 seeds, meaning a mature tree can produce 800,000 seeds. Birds and mammals alike feast on the fruit and seeds, ensuring distribution. Those fruit that aren’t consumed will eventually fall or burst open. The fruit are full of fibers that can carry seeds on the wind. The fruit float and the tough exterior is very durable, allowing them to travel large distances in the water. There is a theory that the ceiba in Africa evolved from fruit that floated there from the Americas, where they originated.

 Cultivation & Uses

One of its many names, silk-cotton tree, comes from the fibers that house the seeds, inside the fruit. This cottony fiber is used for many purposes, most often as stuffing for mattresses, pillows, etc. It was used in life jackets for decades until replaced by synthetics.
The seeds are used for oil that has been used for soap and as fertilizer. They can also be pressed to produce a vegetable oil and this is commercially done in India Indonesia and Malaysia. The oil is also sometimes used as a biofuel and in paint manufacture.
Because of these many uses, a hybrid species has been created which is smaller, produces very high numbers of fruit/fiber pods, and does not have the sharp thorns on the trunk some other species have.

Medicinal Uses
One of the reasons the world tree was sacred to the Mayans was that it provided them with so many things, including medicines. The seeds, leaves, bark and resin, from the kapok tree are used for: dysentery, fevers, venereal diseases, asthma, menstruation bleedings and kidney diseases.