Bamboo is the world’s most useful plant. It is used for making furniture, building homes, for trellises in the garden, as a musical instrument and so much more. In order to use it properly, one must determine the age of the bamboo culm before harvesting.
How can you tell how old bamboo is? There really is no way to know for certain without marking each culm for every year of growth. However, you can get an estimate of age by examining the culm color or by inspecting the branching pattern.
It is important to know the age of the culm that you are about to harvest because it is useful for different things at different ages. Let’s explore how to roughly determine the age of bamboo for your next project.
| AGE | USES |
| <30 Days | Good for Eating |
| 6-9 months | basketry |
| 2-3 years | Bamboo Boards & Laminates |
| 3-6 Years | Construction |
| >6 Years | Begins losing strength |
Related: One of my favorite tools for cutting down bamboo is a simple handsaw. But not just any handsaw. This Japanese handsaw from Amazon cuts bamboo like it’s butter and fits into those tight spaces too!
DETERMINING THE AGE OF BAMBOO THROUGH CULM INSPECTION
The easiest way to get a rough estimate of the age of your bamboo is to inspect the culm itself. As the culm ages, it goes through a transformation that is readily detectable by the naked eye. It is especially important to figure the age of the bamboo culm when used for construction purposes because you want to have the strongest material available to you.
One year old bamboo has a vibrant, emerald green color with outer sheaths just beginning to fall off. There is no presence of lichen yet and minimal branching at the top. These culms tend to look fresh and clean.
You may be tempted to harvest these because they look to be in great shape, but for construction purposes, they are way too young. Best used for basketry or furniture applications.
Bamboo that is 2-3 years old has the formation of white spots on the culm, indicating the growth of lichen. This bamboo can be used to make flooring and laminates as well as used in furniture production.
By the time the bamboo reaches 5-6 years, the lichen is clearly visible. There may also be a buildup of moss around the branches and nodes of the culm. The color of the culms is now looking aged and dull.
Three to six years is the best age for harvesting bamboo for construction purposes. As bamboo grows, it generally has its final diameter determined from the start, but it takes a few years for the inner walls to thicken. Between 3-6 years, these inner walls are at their thickest, strongest points.
As bamboo progresses in age, it can be a little more difficult to determine the age from a culm that is more than 6 years old. The best indicator I have found has been the presence of insect holes. However, these can be hard to discover, with most insects attacking a culm from the inside out. Sometimes you just have to cut a culm down before you realize it is too old to use.
CALCULATING THE AGE OF BAMBOO THROUGH BRANCHING
It is possible to inspect the branching pattern of bamboo to determine its age, but there has been some disagreement on this method.
Every year, bamboo loses its leaves on the branches then new leaves grow in to replace the old leaves. However, when the leaves fall off, they leave a little stub. This stub can be as small as a quarter inch, so you’ll have to look closely.
The new leaf grows just beyond the old stub. Counting the stubs gives you an idea of the number of times (or years) the branch has lost and regrown new leaves.
This method of determining age can get a little more difficult as the culm gets above six years in age. Branches break off, wither and die. You lose the trace marks that help you determine the age, so once again determining if a culm is more than 6 years old proves to be difficult.
Related: Create A Food Forest In Hawai’i
WHEN TO HARVEST BAMBOO FOR CONSTRUCTION
In order to harvest the strongest material possible for construction grade bamboo, it is very important that it is done during the right time of the years.
In Hawai’i, the best time to harvest tends to be a few weeks into the Ku Season, or mid spring, when the new shoots have begun to grow. The bamboo plant sends all the starches to the new growth to help it grow.
At this point the culms that you want to harvest with have less sugars, increasing the strength and its ability to resist attack from insects.
When harvesting bamboo, be sure to just above the node at the base. This way, the bit that is left over doesn’t become an empty vessel, waiting to catch the rain and breed disease and insects. The overall health of your clump depends on proper harvesting techniques.
TREATING BAMBOO
Bamboo is one of the world’s best building materials, but it can be vulnerable to insect damage. Because of this, it is very important to treat bamboo so that it can withstand attack from hungry bugs.
The most common way to treat bamboo is to inject it with a 3%-10% Boric Acid solution through the bamboo with an air compressor with 20 to 30lbs of pressure.
The bamboo is placed at a slight incline with the base elevated nearest the compressor. The air hose is attached to a “Holding tank” filled with the boric acid solution and is attached to the bamboo with a rubber coupling commonly used in plumbing. It takes about 20 minutes for the solution to be forced through the other end of a 20’ bamboo.
Another way to treat bamboo was to leave the bamboo in a river for a couple of days where the running water can leach out any starches that the insects tend to eat. This method is not always available to everyone, hence the boric acid treatment.
Related: Drying and Preserving Bamboo
IN CONCLUSION
Bamboo is one of the world’s most widely used building resources, but it is very much underappreciated in the US. Through the application of stringent building codes that benefit only the conventional materials, bamboo has had a hard time becoming accepted as a building material.
It really is a shame because bamboo has been proven the world over as a viable building material. Especially in the tropical parts of the United States, such as Hawai’i and Florida, bamboo should be allowed to be used as a building material. Until then, bamboo will not be able to showcase its truest potential.
It is important that we, as users of bamboo, learn to harvest and treat it properly to prove to others that it is not as bad of a construction material as they might think. I always have people telling me that it doesn’t last and then I tell them about places in Indonesia and Latin America that have been around for decades.
Harvest bamboo at its proper age, treat it and utilize it with proper design and prove to others that bamboo is a worthy material that can rival pine wood any day.
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