Wide, not deep.
Everyone draws a tree with roots as deep as its crown is high. Almost no tree grows that way, and the kapok least of all. Its roots leave the trunk near the surface and run nearly level, 10 m (33') or longer, in the top 40 to 80 cm (16 to 31") of soil. The deepest roots in tropical dry forest reach only about 3.7 m (12'); the tree above them can be ten times taller.
No one has ever dug up a grown kapok, so this drawing joins the measurements that exist: growth tables from plantations, root excavations of young trees in Panama, the Smithsonian’s giants, and how deep tropical roots go. “In this garden” follows a watered, open-grown tree with a five-month dry season, which the sources put at 25 to 40 m (82 to 131'); “As a forest giant” follows the wet-forest emergents, 50 to 60 m (164 to 197'). Real trees vary with soil, water and luck. This is an illustration, not a forecast.
Four kapoks were planted here in 2015. In 2315 they would be three hundred years old, and only just grown up.
Where the facts come from
- Chinea-Rivera 1990, USDA Forest ServiceGrowth in Costa Rican trials; first flowers; sprouting
- PROTA, Ceiba pentandraSeed size and weight; roots in the top 40–80 cm; buttress size
- World Agroforestry, Agroforestree DatabaseSeed, growth and form
- CIRAD plantation growth tableHeight and trunk by age, 10 to 70 years
- Kurú 2014, Costa RicaSprouting times in Costa Rica
- Rojas-Sandoval, Lobo & Quesada 2008Leaves, flowers and fruit through the Guanacaste year
- Sinacore et al. 2017Root excavations of young trees in Panama
- Crook, Ennos & Banks 1997, Journal of Experimental BotanyWhat buttresses do
- Canadell et al. 1996How deep roots go, by kind of forest
- Jackson et al. 1996How much root lies near the surface
- Smithsonian Tropical Research Institute, Big Tree dataÁrbol Gigante: crown, height, base
- Smithsonian Tropical Research Institute, 2021A fallen giant of 300 years or more
- Monumental TreesThe tallest measured kapok, 60.4 m, Costa Rica
- One Earth, Central American dry forestsThe dry forest’s canopy, about 30 m