Thursday, October 3, 2019

Answer: Why are palm trees so tall?

Palm trees are wonderful, but very strange... 

As you might suspect, they're not ordinary trees, but something very, very different.  

They're generally super-tall, able to remain standing in hurricane force winds.  If you cut one down, you'll see a very strange and wonderful composite structure that looks nothing like an ordinary tree.  There are no tree rings, but a bundle of fibers that are key to its extraordinary resilience. 

P/C Wikimedia / Kadeve.
Our Challenge was:   

1.  Why are palm trees SO tall? 

As you know, asking Why Questions can be really difficult and tricky.  What's a good answer to a why question?  

To get a bit of background, I looked at the Wikipedia entry about palm trees, and quickly ended up on the entry for Arecacae, the latin family name.  There I learned that: 
The Arecaceae .. can be climbers, shrubs, tree-like or stemless plants.. There are 181 genera with around 2600 species are known, most of them restricted to tropical and subtropical climates. Palms are distinguished by their large, compound, evergreen leaves, known as fronds, arranged at the top of an unbranched stem. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type of habitat within their range, from rainforests to deserts...

I started this Challenge by doing an obvious search in the form of a question.  Note that asking questions like this triggers a special kind of Google search processing--it's not just searching for those terms, but the query is handled much more as a knowledge-based request... 

     [ why are palm trees so tall ] 

The search results are pretty good.  

(Click to see at full size.) 
The first 4 results are right on topic and give us a diversity of content.  Here's what I see and think when I look at these hits.  

#1 is a link to a Quora (a well-known question-answering site) discussion with a question about the evolutionary benefit for palms to grow so tall.  That's a great approach to answering the why question--understanding the costs and benefits from an evolutionary perspective would be good. 

#2 (skipping over the "People also ask" section) links to a reddit "Explain like I'm five" question/answer about "why are palm trees so tall?"  The explanation might be simple, but there's almost certainly an interesting discussion there. 

#3 is from Mother Nature News, a kind of gee-whiz site with breathless articles like "4 ways tardigrades are nearly indestructible," but might give us some interesting tidbits about tall palms.  

#4 links to a StackExchange forum, pointing to the more generic question "Why is it beneficial for trees to grow that tall?"  I expect this to be a more general discussion of tree height--perhaps we'll learn something about why trees grow so tall in the first place.  

I read the targets of these links and found out that: 

* Not all palm trees are tall!  (In retrospect, this is obvious--different species of palms have different heights. For instance, the Allagoptera arenaria  (Beach palm) is less than 2 meters high.  But clearly, we're curious about tall palm in this Challenge.)  

* Palm trees in their wild and natural setting often compete for resources.  In the wild, palm forests are often densely packed, requiring the palm trees to do something to grab their own light, water, and nutrients.  Growing extremely tall is one solution.  

Here are a few images of wild palm tree forests. You can see there's a lot of competition for sun and water.  

Eastern San Diego county, packed into the bottom of a dry ravine. 

A palm forest in Indonesia.

Even beach locations can be competitive! (Image by Pexels from Pixabay.) 
(I note that it's a little tricky to find images of palm trees in their wild and unstructured settings.  Many palm trees, even dense forests, are often former coconut plantains, which isn't the same.)  

Result #2 tells us that palms are often the fastest growing trees (although as with palm tree height, growth rates vary from species to species).  So they compete in height, and rate of growth in order to get the resources they need.  

Meanwhile, #3 tells us that the tallest palms are the Quindio wax palm (Ceroxylon quindiuense), growing up to 60 meters (180 feet), which Wikipedia tells us grows in dense forests in the wild--so height is important there as well.  

And #4 asks the more general question, "Why is it beneficial for trees to grow that tall?" Keep in mind that this is a discussion on a StackExchange site that encourages experts to answer and discuss questions.  It's heavily moderated, and the quality of the discussions you find there is pretty high.  

This particular thread discusses why palms in forests grow so tall, and work through various alternative explanations... but it all comes back a fitness advantage for taller trees to have more sunlight.  

An interesting twist...  Just for grins (and because I know that shifting media types sometimes gives an insight), I did a search for: 

     [ palm tree height ] 

and looked at Images.  It was pretty much what you'd expect.  Looked like this in the center of the SERP: 

That scatter plot chart in the middle made me think--perhaps there's something interesting here! 

Turns out that this chart comes from a scientific paper about the age and height of oil palm trees, Tree height and crown shape as results of competitive games (J. of Theoretical Biology, January 1985) and that made me think about doing a search in Google Scholar.  

In Google Scholar: 

     [ palm tree height ] 

led to a bunch of fascinating papers (which time and space prevent me from summarizing, but there's a fun intellectual rathole to explore one day).  

But the paper Competition from below for light and nutrients shifts productivity among tropical species
seemed to potentially hold the answer to our question.  Turns out that it didn't... exactly... but it DOES make the fascinating observation that 

"...In 2 cases the novel competitive mechanism responsible for the shift was reduction in crown volume, and therefore light-capturing capability, of overtopping deciduous trees by intrusive growth from below a palm." 

Which kind of captures what we found elsewhere.  

Why are palm trees so tall?  Answer: Palms compete for light by growing tall and fast.  In this case, they overreach the (ordinary) deciduous trees by growing up and through the canopy to reach the pure sunlight above the shade cover of the deciduous trees.  But in palm forests they're competing with their peers...  where they compete just as hard.  


Search Lessons 

This Challenge points out a couple of lessons to learn and take to heart. 

1. Looking across a number of different sources is valuable.  I know I keep saying this, but as a skilled SRS-er, do NOT lock in on any single result, especially if it confirms your beliefs.  A better strategy is to look broadly across a number of results and look for insights that are reported consistently across a number of different authors, different sources, and different perspectives.  That's one way to find your way to truth.  

2. Try different sources to get a different perspective.  Here I did another (but related) search on Google Scholar (after having been prompted by seeing a scientific chart in an image), and found lots of high-quality (but sometimes dense) articles on palm trees and their growth behaviors.  

Hope you enjoyed this romp through palm tree botany.  As always, there's a LOT more to say about this topic.  (If you're interested, a great query is [ varieties of palm trees ] -- they're an amazing group of plants with wildly varying shapes, sizes, and niches.  As they say, worth a trip...)  

Search on!  


  1. #TheJoyofSearch and also the one that comes reading your answer is always great. Plus reading and learning with other SRS searchers help us to grow.

    Palm trees are amazing. Also are "Patas de Elefante" (Beaucarnea) which I am also SearcreSearching more after this Challenge and one friend's question

    I'll visit the links you share and also like that you added a comment about those sites. With that, we can know more about the answers posted. As you say different sources and perspectives are always welcome. And even more after we know the angle they are covering.

    About the font. I liked it on mobile phone

    1. Today I found 2 interesting articles.

      The first related to Monarch Butterfly :

      The second is about 🌲 Amazon's new tallest tree

    2. I kept SRS after reading Dr. Russell's answer. Tried:

      [Palm trees transversal cut] in all and images. Alamy shows different trunks.

      Also interesting: Palms never stop growing.

      Then with [Palm trees resilience] found why we need to be like Palms and


    3. Hello Dr. Russell
      I like the new look of the post and the new color. Font looks much better in all devices.

    4. Glad you like it. Turns out that the typography issues were caused by an old (and out-of-date) template. I had to update in order to fix the layout issues. Took this chance to update everything!

    5. Thanks Dr. Russell. Also happy you found the issues. Thanks for that too and the new updated photo, color and style.

      I was wondering if it is possible to change for a darker color the links. Sometimes, specially in small screens letters are not as clear to my vision as are with the green in title or the red in Search Lessons

    6. Changed to dark blue. Does this work better for you?

    7. Dark blue is perfect. Thank you 😀

      I usually enter the blog first using ?m=1 and then read the whole part. Also, love that now with the update we have again the way to share in social media (I didn't saw in the previous version for the last months. Although, it could be that I and we were already not noticing because familiarity with the layout.

      Thanks again for the changes and the dark blue

    8. uhhhhh, Dan
      find the new template a tad jarring — a little hard to read, but the variety of colours is nice… ;˚P
      could it be a result of the PG&E cutoffs? it will be a more tranquil world once electricity is punished/banished for all its transgressions…
      a map of earth wind & fire
      PGE page

    9. Remmij -- If that's your screen... you have bigger problems than my theme color choices!

    10. copy that, Dr. Russell… think you hit the nail on the head!
      there's a very outside chance such views -if they really existed- could be Catalina related?, but I'm sure an update is on the way… (the very subtle sound of S.P. Jobs spinning…)
      perhaps the follow-up volume could be "The Joy of Focus" (despondent emoji) ¯\_(ツ)_/¯. glitch happens.

  2. Dan, YOur book now in hand. I had assumed that you meant how did the palms survive SO well in captivity. j

    1. Good news about the book!

      And while that's a plausible interpretation, I meant VERTICAL growth!

  3. Dan heard back from high school classmate who has some serious botany/horticultural cred. Anne and I researched why palm trees in LA in particular grow so tall and this is what my classmate had to say (and felt that reaching out to an expert was OK)
    "From what I know and researched, Washingtonia robusta are not the best for dry, drought areas, even though they come from the drier areas of northern Mexico. They particularly thrive where there are deep pockets of moist soils in there native environments. In public spaces in LA, like you said, they likely get maintenance attention (including irrigation) which optimizes their growth compared to when subjected to the climate stress of northern Mexico."
    So hopefully this helps to answer why these trees grow so tall specifically in LA!