Read the transcript below:

Welcome to the show!

In this podcast, we air episodes within a series so you can jump around and skip to what you are interested in. In this series, we’re going to be covering several plants from the Amazon.

The news recently broke that the Amazon has recently been undergoing an increase in the number of fires that it’s seeing, and the Brazilian government, illegal deforestation, and cattle farming is largely to blame.

Now, I understand that’s a blanket statement and there is a lot going on politically, but that’s not what this podcast is about. This podcast is about the plants that it’s affecting, it’s about the climate, and the ecosystem that we live in – the planet that we call home.

Of course, there are charities and foundations that are asking for money for relief of these fires, but that doesn’t change the fact that we’ve already lost a significant amount of this rainforest and this affects a global ecosystem, even if we do manage to rebuild and repair. As it stands right now, we are losing wildlife, we are losing industrial plants, and we are losing food production crops, and we’re also losing the trees that filter the carbon out of the air.

I mean, not only are these trees filtering the carbon out of the air, but they’re also giving us oxygen back, so you’re not only going to see the air pollution get worse, but you’re also going to see the world climate change. This is the largest rainforest that we have; it affects a significant amount of the world’s climate just from the water that it releases and the oxygen that it produces – so, we’re going to see atmospheric changes, and the soil microbia change, and that affects a larger ecosystem than just the rainforest.

So, without any more delay, let’s start the episode and actually start learning about some of these plants.

Hevea Brasiliensis – The Rubber Tree 

I would like to introduce you to Hevea brasiliensis. It is also called the “Rubber Tree.”

There are hundreds of plants that produce latex, but almost all of the world’s natural rubber is made from latex from this tree. We’re talking about 99% of the natural rubber that we use; and no, not all of the rubber that we use is tapped from wild trees in the Amazon basin. Most of the world’s rubber comes from plantations in Indonesia, Thailand, and Malaysia. Plantations have also recently been dealing with a fungal disease called South American Leaf Blight, so it means that tapping in the basin is still a vital part of the livelihood of many people living in the rainforest; particularly in the Brazilian state of Acre, and parts of Bolivia and Peru.

This practice of harvesting wild rubber has actually been incredibly important for the rainforest. Not only is the rubber there tapped sustainably, but it has also been a driving force in forest conservation.

This is largely thanks to Chico Mendez, a Brazilian rubber tapper who founded the National Council for Rubber Tappers. This was to protest deforestation for cattle grazing. The council was able to obtain what was called “extractive reserves” within Brazil, and this gave them the rights to sustainably harvest goods like rubber latex or tree nuts, and as a side benefit, these rights helped protect the forest from deforestation.

Of course, there are always two sides to the same coin:

While local farmers aid in forest conservation, there has also been a problem with global demand. Global demand has pushed many farmers to clear out other plots of diverse ecosystems to begin planting rubber trees for industrial trade. This chokes out several already-endangered plant and animal species.

Now, when I say natural rubber, one thing that not many people realize is that there are synthetic rubbers as well. Synthetic rubbers are commonly used for making car tires or paints, but natural rubbers from this tree produce some of the smaller objects in our everyday lives, like rubber balls, balloons, bandages, latex gloves, you name it.

But what does this tree actually look like?

This tree can reach a height of up to 140 feet (42.6m) and the usually-white latex occurs outside the bark, mostly outside the phloem, which is the innermost layer of the bark. This layer also transports the organic compounds that aid in photosynthesis, and sugars – sucrose – to where the plant needs it most.

If you actually saw some of the latex and how they collect it – they collect it by tapping the tree like they would with a maple tree, but they use pails to it actually winds up looking a lot like milk.

I really wouldn’t recommend drinking this stuff, though. Sure, a lot of people say it has a neutral to slightly bitter taste, but, I mean, you’re eating tree sap. That’s not very appetizing! If you told me to put this tree sap on my pancakes, I would be a little weirded out, especially if it looked like milk. Thank goodness somebody else taste-tested maple syrup!

Okay. Back on topic. Beyond it looking unappetizing, there is a protein in the latex that many people are allergic to, or at least hyper sensitive to. So, if you have a latex allergy you don’t even want to be near the rubber tree, because you can also inhale the fumes coming from the latex and that can trigger an allergic reaction.

The trunk is generally straight and narrow, and the branches begin to extend in a Y-pattern. The trunk is a right brown color, reminiscent of light leather, and the broad leaves are long and bright green, arranged in a spiral pattern.

One unique thing about this tree is that the fruits, which are a dark brown and look a lot like a brain contain three large seeds on the inside and they explode when they disperse. If you’ve ever seen some of the plants that explode on seed dispersal, it’s actually rather intimidating. I mean, imagine if plants had guns that they grew. That’s pretty intimidating!

Thanks to Biodiversity Shorts for this video on explosive seed dispersal. 

The rubber tree is considered of Least Concern on the endangered species’ lists. It grows natively in low-altitude moist forests, disturbed land areas, forest gaps, wetlands, or riparian zones, which are the landmass between solid land and a river or stream.

I guess what you should take from this is that this tree is an opportunistic little plant who doesn’t give a darn about where it grows, but it likes water.

Nutritional Value of Rubber Tree Seeds

Another interesting thing about this plant is its nutritional value. In testing, the average seed kernel of this tree contains about 21% crude protein, 50% crude fat, 6.5% crude fiber, and 18% carbohydrates. That sounds like an excellent, energizing tree nut, doesn’t it?

…I forgot to mention that they are also incredibly toxic. Fresh seeds contain 164mg of HCN, which also known as cyanide. This is per 100g of dry nut.

Of course, it is also considered a famine food. In dire straits, they could be stored and cooked to remove most of the cyanide and eaten when there is literally nothing else to eat, but chances are, you are also in the middle of the Amazon rainforest here, and you have plenty of other foragable options.

Latex Allergies and the Rubber Tree

We touched on allergic reactions earlier, but let’s dive a little bit deeper into that. What causes it?

There are several proteins within the latex that can cause an allergic reaction in sensitive individuals but two of the most common proteins are HEV B5, which is rich in glutamic acid, and Prohevein, which is involved in the formation of rubber. This helps protect the tree’s wounds by inhibiting fungal growth.

Symptoms to this allergy come on within minute of contact and can manifest in many different forms, including hives, itching, redness of the skin, or eczema-like dermatitis. Asthma-like symptoms of wheezing, chest tightness, and difficulty breathing are also common. In individuals who have severe allergic reactions, it can cause difficulty breathing and shock.

Now, something interesting about this allergy that we don’t usually hear about is that, if you have a latex allergy, you also most likely have food allergies to things like apples, avocados, bananas, carrots, melons, raw potatoes and tomatoes. This is thanks to what is called a cross-reaction where certain foods share similar proteins to the allergen.

Other Uses for the Rubber Tree

There are no verifiable medicinal uses for this tree.

Other uses, aside harvesting the latex for rubber, include harvesting the wood at about 25-30 years of age. This is once the latex is no longer produced. This wood is typically used to make durable flooring and furniture.

Rubber trees support the ecosystem around them by providing food. When the seeds explode and fly outwards, monkeys and birds will seek out the seeds for nutrition – which we did learn that it is a very nutritious seed, despite being toxic to people in its raw form.

If the seeds land in water, large fish capable of cracking the hard seed shell, such as piranha and tambaqui, will feed on it.

The Rubber Tree’s Growing Conditions 

So, what exactly does the rubber tree need to survive? Let’s journey down this path for a minute. What conditions do you need to grow a rubber tree? Which, I mean, I really don’t recommend it, but let’s give this a thought.

This tree is drought tolerant, and it’s very sensitive to cold. It will grow in areas where the temperature is between 23-35 degrees Celsius, which is 73-95 degrees Fahrenheit. So, if you live north of the Equator, you’re going to need a very large greenhouse.

The rubber tree prefers moist soil, with the best soil type being well-draining, loamy soil with natural undergrowth, which also means that you don’t just need the tree, but you also need all the plants underneath the tree – at least, that’s if you want a happy, healthy, and thriving rubber tree. It loves sun and tolerates light shade. 

Seeds are only viable for about a week for germination, however, which brings me to a fun story in this plant’s past.

History of the Rubber Tree

Every plant has a history, a story to share, so what is the rubber tree’s story? 

Once upon a time, Hevea brasiliensis only grew in the Amazon rainforest. The discovery of the “vulcanization procedure”, which is a process that improves the hardness and elasticity of rubber, led to a rubber boom in 1839. Of course, this led to increasing demand all the way into 1913.

In 1873, early attempts were made to grow the rubber tree outside of Brazil. 12 seedlings were successfully germinated at the Royal Botanical Gardens at Kew, and they were sent to India for cultivation. Unfortunately, these seedlings died. 

A second attempt was made in 1875, only two years later, with 70,000 seeds being smuggled into Kew by a man named Henry Wickham. Henry was an explorer who was in service to the British empire. 

Let’s think about that for a second. This wasn’t too long ago, but this was still in a time where explorers were a legitimate career – and you’ll notice in a lot of plant histories that there are a lot of botanists smuggling seeds to Kew and other national botanical societies. There was a lot of intrigue around plants that we don’t think about anymore in today’s culture.

About 2,800 of those 70,000 seeds germinated – roughly four percent – and 2,000 of those were sent to what is now Sri Lanka. About 22 of those seeds were sent to the botanical gardens in Singapore, and this began the successful propagation of the rubber tree in the British colonies. By the 1900s, a rubber plantation popped up on the map in Malaya and that’s how we got today when a lot of our rubber is coming from rubber tree plantations in South America and South Asia. 

Plant Trivia

It’s getting near the end of the show, which means that it’s time for today’s Plant Trivia!

Which type of tree is famous for moving away when it is touched? 

Send your answers in in the comments and find out the answer in the next episode!