Entandrophragma excelsum, an indigenous tree species standing tall in deep in the remote valley of
Mount Kilimanjaro.
By Muhidin Issa Michuzi.
The other day, while surfing through New Scientist online – not to check if AI is finally making coffee (though that would be handy) – I stumbled upon two juicy headlines that stopped me in mid‑scrolling:
- “Why trees can’t grow taller than 100 metres.”
- “Africa’s tallest tree measuring 81.5 metres found on Mount Kilimanjaro.”
As a curious third‑rate journalist and part‑time tree enthusiast, I dug deeper. One headline was about why trees stop growing; the other was about a Tanzanian tree that’s practically knocking on the 100‑metre ceiling. Coincidence? Nature flexing its muscle? Divine providence? I had questions. And oh, did science deliver?
Turns out, even the most ambitious trees eventually hit their skyward limit. No matter how deep their roots go or how inspiring their TED Talk could be (if trees had podcasts), nature simply steps in with a firm interjection: “That’s enough, young trunk.” Kaare Jensen of Harvard University and Maciej Zwieniecki of University of California (UC) at Davis studied a whopping 1925 species of trees and noticed something oddly poetic: the taller the tree, the smaller its leaves. It’s not aesthetics – it’s logistics.
Here’s why: Trees run on sugar. Leaves produce it using sunlight (photosynthesis, if you’re feeling fancy), and then send it on a cross‑country trip down the tree’s phloem – those microscopic sugar highways. But these highways aren’t your normal Arusha–Dar road. They’re more like those winding rural roads full of potholes and goats to avoid. Sugars zoom from the leaf tips, but the further they travel – through the stem, down the trunk – the slower they go. Eventually, it takes so much energy to push those sugars to the roots that the whole operation just says, “Forget it.” Growth stops. Science calls this the transport bottleneck. I call it tree traffic jam. Mathematically, this energy burnout happens somewhere around the 100‑metre mark. Beyond that, it’s not worth the sap. Literally.
Enter Tanzania’s Tree Titan: The Entandrophragma Excelsum. Now that we understand why most trees quit growing while they’re ahead, let’s visit one that clearly didn’t get the memo. Deep in a remote valley on Mount Kilimanjaro stands Africa’s tallest indigenous tree, the Entandrophragma excelsum – a name so majestic it sounds like it deserves a golden sash and a background choir. This gentle giant towers at 81.5 metres, tall enough to make necks sore and egos small.
Spotted and later studied by Dr Andreas Hemp from the University of Bayreuth in Germany, this tree isn’t some overnight sensation. It’s been silently growing for 500 to 600 years. That’s right – this tree is older than the United States, older than Beethoven, older than every Tanzanian president… combined. Hemp first saw these towering trees about 20 years ago while exploring Kilimanjaro’s wild slopes. But back then, measuring their height accurately was like trying to catch moonlight with a fishing net.
With advancements in laser technology (yes, trees now get laser scanned like groceries), Hemp and his team finally measured 32 specimens between 2012 and 2016. What they found was extraordinary. Ten of them stood between 59.2 and 81.5 metres, with trunks so wide you could host a Sunday family meeting inside and still have room for a goat or two.
Why Kilimanjaro? What’s in the soil? This part really fascinated me. Why there? Why not somewhere else in Africa? Turns out, Mount Kilimanjaro is not just tall – it’s generous. Its volcanic soils are nutrient‑rich (thank you, past eruptions). Its warm and humid climate (hello, misty mornings) and abundant rainfall make the right environment for towering vegetation. It’s the perfect leafy cocktail for arboreal greatness.
Think of it like this: if you give a student perfect lighting, good books, free Wi‑Fi, and three meals a day, they’ll most likely excel in their studies. Trees are no different. Kilimanjaro is the Ivy League of Africa’s ecosystems, and Entandrophragma excelsum is top of its class.
But this tree isn’t just showing off. It’s hosting. As Dr Hemp poetically puts it, “They are like a city in the forest.” These massive trees are vertical ecosystems. Their trunks and branches support entire plant communities – ferns, orchids, mosses and even other smaller trees. Birds nest high above the forest floor. Monkeys swing through the canopy like seasoned acrobats. Insects treat the bark like real estate, moving in with no rent, no deed and no permission. In a way, each of these giant trees is an apartment block, a community centre, a pantry and a playground – all in one. It’s urban planning, but greener and with fewer potholes.
But of course, there is a villain: the chainsaw. Call it the dark subplot. Despite their size, beauty and ecological importance, these gentle green giants aren’t safe. Illegal logging has crept into their valleys like a silent thief. Even though these areas lie just outside the protective reach of Kilimanjaro National Park, they remain vulnerable. One chainsaw, and 600 years of growth slump to the ground.
Dr Hemp and his team have pleaded with authorities to extend the park’s protection boundaries to include the valleys where these trees grow. It’s not just about one tree, they argue – it’s about an entire ecosystem hanging in the balance. David Seaborg from the World Rainforest Fund echoes the call. He emphasises that saving these trees also means saving the biodiversity that depends on them – from buzzing bees to the smallest ferns. “These trees are life support systems,” he says. “Lose them, and you lose more than wood – you lose worlds.”
So, what can we learn from Kilimanjaro’s Goliath of the valleys? One: Trees have limits. They are not infinite towers of wood. They grow until physics taps them on the bark and says, “That’s enough, young sapling.” Two: Tanzania is home to a quiet legend – a tree that has defied time, weather and the odds to stand tall and proud while feeding, hosting and protecting others. Three: If we’re not careful, we could lose that legend – not to natural death, but to greed, neglect and bureaucracy.
Final thoughts: Next time you see a tree, don’t just see shade or firewood. See architecture. See silent ambition. See a skyscraper built with sunlight and patience. And if you ever find yourself hiking near Kilimanjaro – pause. Look up. Way up. You might just be in the presence of the 81.5‑metre marvel that dared to dream big.
