(Beforehand I'll excuse myself for my english. If you didn't need to know that you can just ignore it)

There's a network of root-like life forms in the top layers of my planet. They use some kind of synthetic bacteria to get energy out of chemical compounds. Also they use the warmth of the planet to grow... The outer forks of these systems are thinner than human hair. They only start growing when they detect materials the "mother system" can use to mine it and transport it. If a big fork isn't needed any longer it dies and gets eaten by smaller ones.

The biggest roots serve as storage and also function as reliable transport routes through harsh terrains like a desert or even an ocean to link two big systems together.

When two big systems "find" each other, the two biggest roots start winding around each other to share as much surface as possible over which they can pass resources. Eventually they will build towers like that. These "root towers" are the most important part to me because their iconic design should set the background theme of my world. Many animal-like creatures will use them in many different ways. The problem is that I want them to be very thick and up to higher than a mile. I don't worry as much about how the towers can get this high because there's enough carbon and network with trillions of roots will have enough energy left. I worry about why the roots would evolve this way. Now...

Why would they grow like that?

I only have a few explanations and they can't stand on their own.

  1. I'd explain that they grow vertically because the root systems would use pressure and vacuum supported by gravity to send and receive resources.

  2. Another attempt is that they would have to grow way up to reach gases and sunlight which they need to build certain molecules. The system would use these molecules to get a picture of where their resources should be sent to. The higher the concentration of these molecules in a root, the more of the requested resources it gets.

  3. This sounds silly to me, but the root system could use these towers to protect a big (and very high) store of reserves from creatures that eat roots underground but not on the surface. Not energy efficient, but hey...

What I want

I want one single solid explanation to why the towers would grow this big. The readers shouldn't ask themselves much more about the towers and they should just accept that they are a scientifically logical thing to exist.

How far off do you think I am?

Do you have a better explanation than any of mine?

Do you have any other advice for me?

Thank you in advance

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    $\begingroup$ Welcome to worldbuilding. I am not sure you are asking us help with a defined problem, or just submitting your concept for troubleshooting. We can help you with the first, not with the last. Please take the tour and visit the help center for more info. $\endgroup$
    – L.Dutch
    Dec 13, 2018 at 14:53
  • $\begingroup$ One explanation is that during the process of "meeting" one another, as they wind their roots around one another and the growth forces them to grow upwards. $\endgroup$
    – ThatCamal
    Dec 13, 2018 at 15:56
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    $\begingroup$ By fork, do you mean thin root, right? $\endgroup$
    – Mołot
    Dec 13, 2018 at 16:45
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    $\begingroup$ One major consideration: roots cannot share resources faster than they can move them. There's going to be some ratio between the cross sectional area of a root and the surface area of the mating surfaces of the root tower. You'll need to explain why they don't use a simpler solution, such as that of the placenta to create a huge amount of surface area very rapidly in a small volume $\endgroup$
    – Cort Ammon
    Dec 13, 2018 at 17:10
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    $\begingroup$ Typically "towers" are associated either with reaching towards a resource (such as solar energy) or fruiting bodies (like mushrooms) which can spread seeds further. $\endgroup$
    – Cort Ammon
    Dec 13, 2018 at 17:11

3 Answers 3


In a competitive environment such as forests and jungles, plants on Earth need to grow vertically and quickly to outcompete neighbours in the quest for light, which for a plant is essentially food and therefore survival. Extending your canopy above others not only gives you more light, but also restricts the light (and therefore growth) of the plants around you and gives you an advantage in offspring and longevity.

In your world however these plants appear to grow from 'thermal energy', presumably from the ground. So there may be several logical reasons why they need to form towers:

  • Competition - such as Size-Asymmetric competition - The ground is already saturated with existing competing plants, and it is easier to attain 'thermal energy' from atmospheric / sunlight than to displace and compete with them.

  • Reproduction purposes - many large trees have the ability to cast their seeds far and wide. In fact, the further the seed travels, the more resilient the species. Height gives you an advantage in this respect, being an enabler of 'helicopter seeds', spores or transmission of seeds through animals or other inhabitants, whereas on the ground you are severely restricted.

  • Sexual purposes - plants on Earth developed very slowly until Sexual Reproduction, enabling much more biologically diverse and resilient species. Flowering plants are an example, where insects pollenate successful trees, spurring on competition and eliminating mediocre species. In your world, your tower roots may be another form of Sexual Selection, attracting pollinators (or attracting / catching spores or some other gametes) via increased height and capability. This is a strong driving force for evolution, taking precedence in many cases over survival.

The world of plants is wide and varied, and I would not be surprised if you find a close example already extant on Earth.

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    $\begingroup$ + for reproduction. What is described is much like fungi. Then 2 individuals meet each other and produce a reproductive structure. Reproductive structures are usually temporary but just because it is not being maintained it might not disappear. These structures would exist alive and in various states of decay. You might need to have the parents die when they produce this structure, plowing all resources into its generation like slime molds do. $\endgroup$
    – Willk
    Dec 15, 2018 at 15:49


While your plants can grow and thrive underground and just above ground level, they only flower and fruit in high altitude. Originally they existed in more mountainous regions but they have evolved to grow taller as the moved (via seed or root) to lower elevations.

They can spread with roots alone but reproduction via seeds is necessary for their long-term health and for genetic diversity. Animals can eat fallen fruit if these plants are rooted in high altitude regions but of course there's nothing left if fruit falls a mile. So animals have evolved synergistically with the plants to be able to climb or fly high enough to reach the fruit. They spread the seeds through their excrement. Some survives the fall but other amounts aren't excreted until after the animal returns to the ground and goes elsewhere.

Why the plants wouldn't evolve to be able to fruit in lower altitude is a mystery but evolution sometimes takes twists you don't expect. Your world may have, as you suggest, gasses that separate out by air pressure that the plants need. Or it may have a cloud or ozone layer that the plants must go above.


For the Plant species to Survive, they've been forced to chase the sky

These structures are used in mating and seed propagation, which requires pollinators to accomplish.

Previously these pollinators were able to live close to the ground, but for some reason, evolution pushed these pollinators high into the sky. Possibly due to their diet becoming skybound, a new predator scaring them off, or an environmental change that forced them skyward.

As time progressed, these pollinators only fly higher and higher, to where the plant structures then had to reach ever higher to perform their reproductive purposes.

These structures may be topped by nests of these pollinators, potentially being the only safe home for these beings today.


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