Buttress root

Buttress roots of a Bay fig tree at South Coast Botanical Garden in Palos Verdes, California

Buttress roots of a colossal cotton-silk kapok in Lal Bagh gardens in Bangalore (Bengaluru), India

Buttress roots,also known asplank roots,are large, widerootson all sides of a shallowly rootedtree.Typically, they are found in nutrient-poortropical forestsoilsthat may not be very deep. They may prevent the tree from falling over (hence the namebuttress).

Buttresses are tension elements, being larger on the side away from the stress of asymmetrical canopies.The roots may intertwine with buttress roots from other trees and create an intricate mesh, which may help support trees surrounding it. They can grow up to 30 feet (9 m) tall, spread for 100 ft (30 m) above the soil, and then continue another 100 feet below. When the roots spread horizontally, they are able to cover a wider area for collecting nutrients. They stay near the upper soil layer because all the main nutrients are found there.

Buttress roots vary greatly in size from barely discernable to many square yards (square meters) of surface. The largest for which there is photographic evidence is a Moreton Bay Fig (Ficus macrophylla) at Fig Tree Pocket (an outlying district ofBrisbane,Queensland) which was photographed in 1866 with an adult man. The buttresses were 40 to 50 ft (12 to 15 m) long and 35 to 40 ft (11 to 12 m) in height.Halfway out the buttress is twice the height of the man. The tree died in 1893 from flood damage.

The tallest buttresses are those ofHuberodendron(Bombacaceae) of theAmazon basinwhich extend up to 70 ft (21 m) up a tree about 145 ft (44 m) in height.

The most extensive buttresses are those of the Kapok, or Silk Cotton Tree (Ceiba pentandra), of theNeotropicsand tropical Africa. The buttresses can extend outwards as much as 65 ft (20 m) from the tree as buttresses, then continue as superficial roots for a total of 165 ft (50 m).

Notable and historic specimen trees with buttress roots

• Ceiba pentandraofVieques, Puerto Rico
• Moreton Bay fig(Ficus macrophylla) in Queensland, Australia
• Jackfruit(Artocarpus heterophyllus), India
• Terminalia arjuna,India
• Koompassia excelsa,Southeast Asia

Gallery

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  Buttress roots. Jensen's Crossing nearCooktown,Australia. 1988
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  Buttress roots ofTerminalia arjuna
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  A buttress root system provides structural support.
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  Buttress roots of an especially largeCeibatree near shore of Amazon River, close to Iquitos, Peru
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  The large buttress roots ofKoompassia excelsa