Bambusa Blumeana - thorny bamboo — Better Bamboo Buildings

This species of bamboo continues to intrigue me as I kept coming across it in my work and pre-covid travels to various countries. Bambusa Blumeana (BB in short) is usually included in the list of bamboo species that are considered structural bamboo and used for construction in their respective regions.

Latin name, Region, Diameter

Guadua angustifolia Kunth (guadua), Americas, 120-160 mm
Dendrocalamus strictus (calcutta), Asia, 25-80 mm
Bambusa Vulgaris (common), Africa, Asia, America, 80-150 mm
Phyllostachys edulis (moso), Asia, 120-180 mm
Dendrocalamus asper (petung), Asia, Americas, 80-200 mm
Bambusa blumeana (spiny/thorny), Asia, Asia Pacific, 60-150 mm
Gigantochloa apus (tali), Asia, 40-100 mm
Thyrsostachys oliveri (tam vong), Asia, 50-70mm

A mature clump of Bambusa Blumeana or The Gai in Vietnam with its thorny branches being taken off. - Photo by The Bamboo Master

I have worked with BB in Indonesia, Malaysia (it is a native to both countries) and also the Philippines. I must say that BB has notable differences in each of these countries, including Vietnam which we will see later. from the commentaries.

BB has its own common name in each country or region as shown below:

Generally : spiny or thorny bamboo
Indonesia: bambu duri (Indonesian), haur cucuk (Sundanese),
Malaysia: buluh duri, buluh sikai
Philippines: kawayan tinik (Tagalog), batakan (Bisaya),
Cambodia: rüssèi roliëk
Laos: phaix ba:nz
Thailand: mai si suk , phai-sisuk
Vietnam: tre gai, tre lá ngắn
China/Taiwan: ci zhu (Taiwan, as B. stenostachya), ci ce zhu (as B. spinosa), yu zhu.
Japan: shi chiku

Bambusa Blumeana or Kawayan Tinik just harvested in the Philippines.

And here are some of its characteristics:

Family : Poaceae Culm length: 15m to 25m
Culm diameter: 8-15cm
Internode length: 25-35 cm
Wall thickness: 10-20mm, thick wall especially towards base

Growth habit: Dense clumping, invasive only in certain areas. Thorny spikes with slightly arching green culms. Culm diameter and internode length vary greatly. Clustered branches spring out from the higher nodes with tough, sharp thorns. Used often for land rehabilitation, living fences, windbreaks or erosion prevention along streams.

Ray and Amy Villanueva of Kawayan Collective are one of the largest producers of treated BB/Kawayan Tinik and they will give us a concise commentary on harvesting/treatment, design and construction based on their good work being done in the Philippines (see our blog post on Kawayan Collective).

Photo : Kawayan Collective - twisty Kawayan Tinik arriving at the factory.

Harvesting, Treatment and Seasoning

Kawayan Tinik, or bambusa blumeana, is the primary species we process at Kawayan Collective. We work with over 40 farmers/harvesters in the mountains of the Province of Negros Oriental to identify mature culms, practice sustainable harvesting, and haul the poles to our treatment facility.

Harvesting kawayan tinik is not easy. Known for its two to three meter tall thorny underbrush, upon first glance tinik is not inviting. These thorns make it very hard for tinik to be cut as it should be - at the base of the culm. Many harvesters who do not practice sustainable harvesting use ladders to climb above the thorns which leaves the bottom of the clump crowded and difficult to access.

This crowded situation also makes it hard for the new shoots to thrive since they have to compete for space and sunlight. In our quarterly harvester meetings, we review best practices - the thorny branches of clumps must be trimmed regularly - and our procurement team regularly checks on conditions of clumps in the field.

To ensure our bamboo is powder beetle and termite-free every piece must go through the four-step process shown in the following video.

Step 1: Washing - Bamboo naturally contains a lot of starch. By submerging the fresh-cut bamboo completely in running water for a few days, we are able to remove the starch that the powder beetle finds so tasty.

Step 2: Drying - By sun-drying our poles for at least 5 days, we reduce the moisture content of the pole to about 33% -- thereby preparing the pole to be able to absorb the maximum amount needed for treatment.

Step 3: Treatment - Every pole is fully submerged to absorb the maximum amount that’s needed for treatment. We use a boron or permethrin solution and this is the final guarantee against termites.

There is no waste in our process because the poles go into the solution already cleaned and dried so that the treatment never needs to be replaced, only added to as the poles soak up more solution.

Step 4: Seasoning - Finally, all our treated bamboo is carefully stowed in covered storage racks that allow for airflow while keeping the bamboo out of the sun and rain.

Treated bamboo will last as long as any treated wood. With proper design, bamboo will last a lifetime.

Design & Construction

Designing and building with kawayan tinik can be frustrating for those who like straight consistent lines. All bamboo is not straight, but kawayan tinik is particularly curvy and tapers significantly from the top to bottom of a culm. Regardless, kawayan tinik is a great option for construction. Our partner, Base Bahay, has developed its cement bamboo frame technology using kawayan tinik for the social housing program they are leading. This building system has been certified by the National Housing Authority of the Philippines as an “innovative technology for housing”. Test houses have proven that it can withstand over 250 kph winds and major seismic events.

Kawayan Tinik used in Base Bahay housing.

As a supplier for these projects, Kawayan Collective uses a strict visual grading process to ensure that the bamboo used in the system meets structural and quality standards. Specifically, we check poles for diameter, wall thickness, taper, node-to-node spacing, and curvature.

Outside of this system, these same poles can be used as construction grade poles for any project. However, designing and building with kawayan tinik requires the same design considerations for any other bamboo (or wood).

We use kawayan tinik because it is the most common species found in our area. In the past 20 plus years, the Philippines Department of Environment and Natural Resources has used kawayan tinik to stabilize river banks in the mountains. National Green Programs have encouraged planting bamboo. It has proven as an effective strategy to protect people from landslides and flash floods and a much better strategy than concrete spillways.

There are definitely other stronger and straighter bamboos in the world, but we love kawayan tinik and all its idiosyncrasies. It is amazing that this plant can revive land, protect lives, fight climate change, employ farmers and artisans, shelter families, and celebrate the uniqueness of being Filipino.

Thank you , Ray and Amy for your sharing. Still with the Philippines, we have another contribution from M3 who is a seasoned bamboo advocate and practitioner:

Besides the normal tinik poles, there is the Gu-od portion (which is the base of the tinik) . These are on the average 245 to 300cm in height. They are harvested a year after the Bu-los (the pole above the Gu-od) is harvested. This practice ensures that the successive culms do not splay out. In addition, for the healthier clumps, we invest in an anti-splaying ring made of 12mm rebar at the 3 meter height to help control too much pole leaning/splaying.

Photo of Kawayan Tinik clump by M3 - some upper culms have been harvested leaving the lower culm to retain the remaining culms and avoiding too much splaying.

Another interesting occurrence that M3 notes is that the more mature tinik (+4 years) tend to have a yellowing or sunburn on the western (sun drenched) face.

Photo of a spray of Kawayan Tinik columns by M3

Photo of sectioned Kawayan Tinik made into a screen by M3.

James and Lam Wolf of The Bamboo Master Company in Vietnam works with BB or Tre Gai in their plantation and factory in Vietnam (find out more about James in our previous article). With the Tre Gai they mass produce bamboo furniture and accessories designed in-house or from clients.

Here is what James has to say about Tre Gai:

The Vietnamese word for bamboo is TRE (pronounced like “tray”) and the word for thorn in is GAI. With a base that’s protected by a dense weave of thorny branches, this bamboo is appropriately named TRE GAI. This stuff is like bamboo on Viagra; thick, hard and long-lasting!

It is low in sugars and starch with makes it resistant to bug infestations and the wall thickness is commonly thicker than an inch. It is incredibly strong and durable, and the only downsides to it are that it doesn’t grow that straight and the thorns tend to scratch the surface, so it’s common to have more cosmetic blemishes than the non-thorny bamboos. This type of bamboo would be my first choice for anything that requires immense strength but where cosmetics can take a back seat to overall performance.

I first starting working with Tre Gai around 1996 in Vietnam. Back in the mid to late 1990’s I was setting up prefab house production in Vietnam for the Hawaii company Bamboo Living, and Bambusa Blumeana was the material of choice for all the framework. Later the company worked with engineers and testing facilities to gain approval to construct houses on Hawaii that were approved by the strict building code authorities in the United States. Tre Gai is the only bamboo that has passed building code in USA.

Bambusa Blumeana or Tre’Gai in Vietnam, Photo by The Bamboo Master Company.

Harvesting, Treatment and Seasoning

Although there are many types of thorny bamboo in existence, in Vietnam all of them are referred to as Tre Gai (thorny bamboo). This can lead to some confusion, so the variable becomes the location they come from. As bamboos native range is usually pretty site specific, local knowledge will fill in the unknown. Just as we might refer to Japanese eggplant or Italian eggplant, the location becomes the modifier, and through experience we know how they are different.

Harvesting this species is very challenging because you need to get around or through the thorns. One method is to hack through the thorny net until you get to the culms and the other is to climb about 3 meters up a ladder, make a makeshift platform on top of the thorny net and harvest the top of the poles first, then work the lower section out.

On top of working in hot tropical climates, sloped terrain, and jungle, you also have to be careful of working on a ladder in a thorny mess. It’s no easy job to harvest this species, but they are worth the effort. Since its usually curved or wavy, you have less stacking efficiency in transporting them compared to straight poles, making them cost even more to attain.

Tre’Gai being harvested in Vietnam by The Bamboo Master Company.

When treating, we often like to punch a hole through the nodal diaphragm to allow internal passage for the treatment solution. With conventional poles this isn’t too hard, but the nodes in Tre Gai can be so thick that this is not always a viable option. In this case some chose to drill a small hole through the wall above and below each node. When drying poles with such thick walls, the tension that occurs may cause hairline splits, but since this bamboo is so strong, these are usually only cosmetic and do not split past the nodes.

Treated and seasoned The Gai, notice the super thick walls - , Photo by The Bamboo Master Company.

Design & Construction

I really enjoy working with this bamboo for quick, down and dirty functional sheds, storage structures, warehouses and truss work. You can easily bolt it with threaded rods, screws and even nails wont split it. It’s sturdiness and bug resistance give me peace of mind that it will last decades and remain dependably strong. I also use this bamboo in furniture and product designs.

The Gai close-up - Photo by The Bamboo Master Company.

The main hurdle is managing customer expectations with regards to the surface blemishes. There’s a trade-off, you don’t have a smooth and beautiful blemish free surface, but you do get exceptional strength and very little concern for bug issues when you choose this species. I built the columns and roof trusses of my own house with Tre Gai for these reasons.

The Gai laths or planks - , Photo by The Bamboo Master Company.

I would say that of the 1,500 to 2,000 different types of bamboo that there are just about 5 or 6 of them that have real commercial and practical applications, and I would place this type in the top 3!

Tre Gai in the factory - , Photo by The Bamboo Master Company.

Thank you , James for your Treat Gai contribution!

My own experience with BB or Duri as it is called in Bali is that it arrives to the factory as twisty with thick walls and nodes. It is more stocky, plump and curvy than its Philippines or Malaysian relatives perhaps from lack of pruning (the wild Duri tend to twist and turn as they shoot up among the many branches of the clump).

Duri is predominantly used sliced as sections and for what is called ‘bamboo bone’ screens (see last photo below). Duri has also been made into balustrading, furniture parts and accessories – for its curves and natural irregularity - this is evident in the Green School and Green Village buildings in Bali.

A Duri feature stair handrail at the Kul Kul Farm, Bali.

In the Philippines BB generally have longer internodes than their counterparts grown in Vietnam, Indonesia and Malaysia. The culms are therefore more slender and ‘uniform’ if you like and they are more commonly used for posts and beam construction traditionally.

Bambusa Blumeana applied as staircase handrails in Kamsia House by TENTEN Design.

Variation in internode length, culm wall thickness, density of branches and straightness of culms is noticeable in each of the countries mentioned. And these differences lead to its variety of applications ranging from structural bamboo to furniture parts.

All in all, Bambusa Blumeana is an extraordinary bamboo species that will continue to have high design and construction value. It is naturally irregular by way of how it grows and has special properties like its really thick wall and often twist and turn lines. Let’s keep building and innovating with it.