Dendrocalamus Asper - giant bamboo

A clump of Asper in Bali - photo by Gomzi.

There are more than 30 species of bamboo in the tropical and sub-tropical zones that are predominantly used for full culm construction with the top three being:

- Moso bamboo (Phyllostachys edulis), 

- Guadua (Guadua angustifolia Kunth) and 

- Giant bamboo (Dendrocalamus asper) 

Many bamboo people call Dendocalamus asper as Asper almost fondly like a friend. ‘Petung’ as I first learnt how to call it in Bali, is a bamboo that is the strongest and largest of the three above (Schröder 2012; Escamilla and Habert 2014; Benton 2015). There are many prime examples of how Asper has been used for the main structural support members in construction especially in Indonesia and this is increasing rapidly. A good place to view the concentrated application of full culm Asper for the main structural supports in buildings would be the Green School and Green Village in Bali.

Asper structural culms supporting 2 levels of classroom and high roof above at Green School, Bali.

Like many other bamboo species, Asper is known by its own local or common name in other countries and regions:

Generally - giant bamboo, sweet bamboo, rough bamboo, timber bamboo

Indonesia – petung, betung (Indonesian), awi bitung (Sundanese), buluh batung (Batak)

Malaysia -  beting, betong, buloh, pering

Philippines - bukawe (Tagalog), botong (Bikol), butong (Visayan).

Thailand -  phai-tong

Vietnam -  manh tong, tre manhtong, manh tong, cay truc

Sri Lanka – una

Taiwan - malai mazhu, malai tian long zhu, malai juzhu

China – dragon bamboo

Myanmar - kyalway-wa 

Laos - hok

Singapore - rebong china

Double Asper culms used as arch structural supports for a resort living space in Indonesia - photo by Javier Diaz.

Asper should not to be confused with the other cousin species under the dendocalamus genus that can look similar to the untrained eye. These are d.strictus, d.giganteus and d.latiforus. Check out the Plant names, Melbourne University paper referenced later for more information on this.

Close up of an Asper clump - photo by Gomzi.

As a plant or grass, here are some of its characteristics:

 Family : Poaceae

Culm color: Culms are grayish green, becoming brown. Lower culm nodes are ‘”bearded” with roots and sometimes covered by a thin brownish felt.

Culm length: 20m up to 30 m

Culm diameter: 15-20 cm

Internode length: 25-60 cm

Wall thickness: 11-20mm, thick wall especially towards base

Growth habit: dense clumping, non invasive

Climate: tropical, sub-tropical

Soils: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: acid, neutral and basic (alkaline) soils and can grow in very acidic and very alkaline soils. It cannot grow well in the shade. It prefers moist, well drained soil.

Hardiness : can grow up to - 4°C

Propogation: can be grown from rhizomes or branch cuttings, in addition to seeds and tissue culture.

 Origin - South East Asia mainly Andaman Islands, Bangladesh, Borneo, Indonesia, Laos, Malaysia, Myanmar, New Guinea, Philippines, Thailand, Vietnam and China SE SW, Taiwan

Introduced widely across: Latin America, Africa and Papua New Guinea, Brazil, Colombia, Ecuador, Puerto Rico, Sri Lanka

Asper mid section culms being offloaded - PT Bamboo Pure , Bali.

Asper has fairly tall and relatively straight culms (perhaps not as straight as Moso or Guadua) which makes it useful for construction. It is of course strong and proven as structural bamboo. Being commonly available across Asia as well as with its ease of harvesting, Asper has been used in many major bamboo buildings across the tropics.

What are the characteristics of Asper as a construction material?

A 12 metre long Asper pole can be carried by 2 persons - this makes working with it on site a lot easier and artisan can lift and move poles around at high level with the assistance of ropes and pulleys if so required. 

I have worked with Asper in many buildings in Bali and overseas and built my own house with it. The Asper used in my house in Bali has proven strong and flexible having withstood the 5 August 2018 Lombok 6.9 scale earthquake with us in the house as it occurred. The house did not have any damage despite the severity of the quake and we did not have to make any repairs at all. While many masonry buildings shook and cracked during the earthquake our little bamboo house flexed and swayed for at least a few minutes but there was no damage, not even any displaced connections.

Asper floor beams and support columns.

Asper has beautiful skin texture and feel. I like that Asper is not as uniform or straight as Guadua - Asper tapers quite a bit more and this adds character to the bamboo structure if one can apply it effectively in their design. The internodes curve gently inwards towards the pole centre almost like a waist giving it this unstraight and wavy line along its length. The mid section of the culm, where there is more regularity in diameter and wall thickness, is used for columns, floor beams, arches, roof purlins and ridge beams.

Full culm Asper at 12 metres long harvested with wide root bases.

The Asper culm base widens and thickens towards the ground more than many bamboo species. This is a feature that has been used where the wide tapering base diameter is carved to sit on a river rock giving the junction with the floor an elephant’s feet look. However it is useful to note that during harvest if we cut off the culm at the rhizome that low in the ground – it will stop a new baby bamboo from shooting up the next wet season. A sacrifice one has to pay for getting the desired look.

Asper columns (two storeys) and double floor beams used in this house structure.

 Apart from using it as a full culm, Asper is also cut into halves, splits/laths, and processed into more engineered building components like planks, beams, and laminated bamboo for both for structural and general building purposes.

Asper long rods bound around a bamboo core to form curvable beams/purlins or arches..

Some of the other structural components that Asper is processed into include split beams (splits bound or glued together) and curved purlins (rods of Asper bound around a bamboo core as photo above). The Asper splits can be formed into floor planks (see photo below).

Asper splits pinned and glued together to form bamboo planks - supported by black asper floor joists (Dendrocalamus Asper niger).

All in all, Asper is a strong, good looking, characteristic and reliable bamboo species. It looks very good with its natural color when installed but it does look even better in black (Dendrocalamus asper niger) as shown by the floor beams in the above photo - but that is perhaps the subject of another article.

Heart of School building in the Green School, Bali.

The Heart of School building in Green School Bali is one of the best examples of multiple Asper full culm usage - the above photo illustrates its use as multiple columns, perimeter beams and radiating floor joists. In its construction during 2012, this 20 metre tall 2000 sq.metre building used more than 2600 bamboo poles out of which at least a few hundred would be Asper.

Asper will still be relevant and consistently used as structural construction bamboo especially in areas where it is endemic because of its availability, strength and character. And of course, Asper looks so good - here is a photo showing off its radiant natural golden colour!

 References:

Plant Resources South East Asia , S. Dransfield & E.A. Widjaja

 https://uses.plantnet-project.org/en/Dendrocalamus_asper_(PROSEA)

Guadua bamboo, https://www.guaduabamboo.com/blog/dendrocalamus-asper

Plant Names, Univ of Melb, http://www.plantnames.unimelb.edu.au/Sorting/Dendrocalamus.html