In Larry Niven's novel Ringworld, there is a scene over the field of "sunflowers" that badly burn Speaker.

Won't those plants eventually take over the whole of Ringworld? Or do they have some sort of natural enemy?

  • Seems to me that the question kinda assumes that none of the hominid species currently inhabiting the Ringworld could possibly take effective steps to stop sunflower expansion; only a hypothetical "natural enemy" of sunflowers could possibly make a lasting difference?. My faith in human (or "hominid") ingenuity is rather greater than that. (Even setting aside the question of what happens if protectors or any spacefaring "immigrants" to the Ringworld decide to take an active interest in dealing with the problem.)
    – Lorendiac
    Dec 16, 2016 at 1:22
  • I don't mean to assume that, but yes that what I was thinking. They way I read it, they are impervious to almost everything short of some space ship with ray guns. Would the primitive tech of the humanoids be enough to stop them?
    – Caleb
    Dec 16, 2016 at 19:02
  • And thanks @Blackwood for the edit. Didn't notice that it split up the words.
    – Caleb
    Dec 16, 2016 at 19:04
  • @Caleb Interesting. In my interpretation, ray guns are one of the few things they would be impervious to. Other than their mirrored petals and crude sensory and motor faculties, they seem to just be regular herbaceous plants, and completely helpless at night. Dec 16, 2016 at 20:05
  • Indeed. I misspoke. I simply meant some sort of weapon beyond primitive ballistics. A ray gun would be pretty useless wouldn't it!
    – Caleb
    Dec 16, 2016 at 20:11

2 Answers 2


As explained in World of Ptavvs, the sunflowers are under the control of the Tnuctip, something that Kzanol is too dim to figure out but that Greenberg does. So whether they have a natural enemy is only one part of the question, and to an extent besides the point. They are artificial, and have a control interface. An enterprising hominid species simply needs to find it and hit the off switch.

As for "natural" enemies: A hominid who doesn't know their control interface but that finds them a threat to itself, its family, or its species, is their enemy. Never underestimate the ability or the will, to just kill off stuff wholesale, of the group that is responsible for the Holocene Extinction.

And sunflowers do appear to be a genetically engineered monoculture. Our enterprising hominids, adept at such biological warfare as the use of myxomatosis to kill rabbits, just needs to find the right strain of Sunflower Root Rot, or Bulb Blight. A sunflower will have a spot of difficulty attacking a disease that is transmitted below ground.

Then there's the minor point that they are obviously vulnerable when the shadow squares are hiding the sun. Our enterprising hominids know how make mirrors and dig tunnels, moreover.

They also know how to farm, and the joy of hyperintensive agriculture. Give them a nice source of ultra-tough reflective stuff, and before you know it they'll be sewing together shiny protective suits made of harvested sunflower leaves and doing to sunflowers what they do to bananas, tea, wheat, cotton, rice, olives, and oranges.

Sunflowers have a good defence against predation; but that does not mean that they are invulnerable, or that they lack predators. Or that they stand much of a chance against hominids that have decided that We like your species; we think that we'll like you on the wall over the fireplace, stuffed.

Nor should we ignore the possibility that they could acquire a parasite plant or two. "What? You'll send lots of juicy sunlight my way in a vain attempt to kill me and you'll kill off all of my competitors? Why, thank you very much, M. Host Plant!" Think of it as evolution in action. ☺

  • 1
    Your comments about shadow squares and tunneling are pretty much what I was thinking. Hominids are much smarter than flowers. If a society with lots of manpower felt severely threatened by sunflowers spreading toward the homeland, it could dig tunnels into the edge of sunflower territory, go in there at night, chop down sunflowers like crazy, and retreat through the tunnels so the warriors are out of the sunflowers' line-of-sight when the sun reappears. Repeat the process nightly for a few years, and you've reclaimed a lot of territory. Doesn't require "control codes" or biological warfare.
    – Lorendiac
    Dec 17, 2016 at 18:07

They could...but not completely.

Tor.com on Sunflowers (on the 40th Anniversary of Ringworld)

Even so, sunflowers will never take over the entire structure’s land area. Sunflowers need carbon dioxide to live and this comes from microbes and animals. There are no geological processes on the Ringworld to hold and recycle carbon dioxide, except the Spill Mountains.

So, while sunflowers can eventually take over much of the Ringworld they need to let at least microbes survive. This doesn’t mean that there wouldn’t be animals, and that they wouldn’t be sentient. After all, since the sunflowers don’t have any way to maintain the Ringworld, they need to leave some sentients around who can maintain the place.

  • 1
    The article you've quoted seems to be almost completely speculative, imagining all kinds of abilities the sunflowers might have, irregardless of whether such things are mentioned in the text.
    – Valorum
    Dec 15, 2016 at 23:20
  • 3
    @Valorum is right. And while I can see sunflowers and soil microbes reaching some balance, "they need to leave some sentients around" demonstrates a really bad understanding of evolution.
    – Spencer
    Dec 15, 2016 at 23:57
  • 1
    Not only is the article speculative, it is incompetent speculation. For instance, postulating sunflower fields as high-resolution imaging interferometers shows a complete lack of understanding of how such an instrument works. At the least, maintaining relative phase between individual flowers to fractions of a wavelength is pretty ludicrous, not to mention sharing relative phase shifts between flowers. Dec 16, 2016 at 0:19
  • 2
    @Valorum While I agree that the article is speculative, I think the speculation might be reasonable if we just assume that sunflowers need carbon dioxide. If sunflowers killed off too many carbon dioxide producers, they would themselves start to die off from lack of carbon dioxide. That kind of biological equilibrium is common. I do agree that there is nothing to say that the surviving carbon dioxide producers need to be sentient.
    – Blackwood
    Dec 16, 2016 at 1:04
  • 3
    How would flowers know to leave some animals alive to balance the ecosystem? Dec 16, 2016 at 2:18

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