Everybody knows what plants are. They’re those boring green things that always die because you forgot to water them. They don’t do much. Mostly they sit around and get eaten by the cat, or if you’re lucky they bloom with a flower every so often or drop an apple from a branch. Some of them are good for building houses or bonfires, and that’s about it. While that may be mostly true for houseplants and the tame little trees humans grow in orchards, plants in the wild have a life of their own, and some of them have answered the struggle for survival by getting up to some strange stuff.
1. Eat Animals
Anybody who’s ever killed a fern can tell you that plants have needs. Plants need sunshine and water, and most of them require some dirt to suck nutrients out of through their roots. Ordinary people, as opposed to plant scientists, usually only have a sketchy idea of what plants extract from the soil, but we know the kind of dirt they thrive in is expensive and comes in bags from the hardware store. It turns out that most of what plants are getting from that pricey dirt is nitrogen, which they use to something-something-plant-chemistry. In environments where the soil is deficient in nitrogen, however, the native plants have had to turn to an alternative source of fertilizer: animals.
Several plants have evolved the knack of eating animals, and in every case, it feels like a violation of the natural order, like those creepy spiders that eat birds. One species of carnivorous plant we’re all familiar with is the Venus flytrap. These small plants live on the East Coast of the United States and use a unique folded leaf structure to “bite” down on small crawly things that get too curious. Inside the plants’ maw, little hairs wait for the slightest brush. When a fly (or whatever is small enough to fit in there) trips one hair, nothing happens. When it triggers the second hair, however, a rapid chemical cascade changes the leaf’s shape and slams the trap closed. Conveniently positioned thorns act as teeth to keep the fly inside, where it dies and fertilizes the plant, not in that order.
Other carnivorous plants include the pitcher plant, which lures in bugs with sweet-smelling nectar and then drowns them, and the whopping 194 different species of Drosera, known as sundews, use a kind of sticky glue to imprison insects. If you’re relaxed about this because you’re not a stupid bug, don’t celebrate yet – there are an Indonesian species of carnivorous plant that grows as tall as a house and eats mice.
2. Walk Around
If the thought of meat-eating plants doesn’t faze you, it’s possibly because no matter how flesh-crazed they get, they’re still just wild plants; it’s not like they can chase you around. Well, nobody has ever found a fast tree before, but one species of South American palm does seem to be able to walk, and it does seem to do this in response to hunger, albeit for sunlight.
The Ecuadorian walking palm grows in the late-secondary rainforest, which is what you get when a virgin rainforest burns down or gets cleared, and new, fast-growing plant varieties creep in. This is a competitive environment, with every green thing trying to grow fast and throw shade on every other green stuff. Here and there, the ground is dappled with sunlight that manages to peep through. The walking palm needs sun like every other plant, but it grows too slowly to reach the canopy first, so it has a frankly disturbing solution to the problem: it walks toward the sunlight.
Not fast, of course. The palm has a trunk that terminates near the ground in a bunch of small branchlike structures, its “legs.” When one side of the palm is in the shade for too long, the roots on that side die and fall off, while new roots grow out of the sunny side and seek the ground. Throughout about two or three years, the main trunk gradually shifts onto the new center, having displaced by up to a few feet. The palm can keep this up all its life. It should be noted that some killjoy scientists say this is a myth, and they have important papers written in a university to prove it, while other, far cooler scientists who live near these things say they’ve seen it with their own eyes.
3. Stockpile Chemical Weapons
It’s a jungle out there, literally. If a plant is going to survive the rough world without being able to move around (some trees excepted), they’re going to have to fight dirty. When German and Allied armies found themselves rooted in fixed locations during World War I, they tried to break the stalemate with noxious chemical warfare that left the enemy gasping and dying. Plants, in a similar trench war with herbivorous animals, have hit on the same solution.
Some plants try to get an edge in the struggle over turf by literally poisoning the soil around them to kill off weeds, which in this context means everything that might send out roots to take their precious nitrogen. Walnuts and hickory trees, for instance, often have little rings of bare soil around their base, and sometimes this dead zone reaches out as far as their branches can go. This is because almost every part of these plants is dripping with a toxic herbicide called juglone (5 hydroxy-1,4- naphthoquinone, if ya nasty) that strangles potential rivals in their cradle. The chemical leaches out of the trees’ roots and exudes from dropped leaves and nut hulls, and the phenomenon has been known to wreck the careful plans of suburban gardeners who want a beautiful walnut tree on their lawn.
Other, more proactive killers use a pesticide called tannin to deter animals from eating their leaves. Acacias are especially rich in tannin, which they seem to stockpile in response to giraffe predation. The acacia and the giraffe have been locked in an arms race for at least hundreds of thousands of years, where the acacias have grown huge thorns, and the giraffes have grown tough 18-inch-long tongues to get around them. The acacias have overproduced tannin, to the point that almost nothing in the world can eat them now, only to have the giraffes evolve large livers that can detoxify the leaves during digestion. The average acacia now stocks enough tannin (the chemical in red wine that gives you a migraine) to kill dozens of humans, if those humans were stupid and ate all the leaves of an acacia.
4. Communicate With Each Other
The race between acacias and giraffes doesn’t end with Alien-style acid blood for the trees. They’re also coordinating their poison production to stick it to the giraffes once and for all. Tannin, like any other chemical, takes a certain amount of energy to produce in any quantity. Production on the insane level acacias are obliged to undertake very costly for the plants, and that’s energy that could be put to better use making seeds and leaves, rather than brewing poison like a Japanese cultist (too soon?). Ideally, an acacia would be able to produce enough toxin to make a giraffe sick and then keep it around until it’s needed.
That’s where communication comes in between trees. Acacias grow in groves, and when a group of giraffes shows up to start eating them, the first tree to get bitten squeezes its tissues to push as much tannin as possible into the leaves. This takes a few minutes, during which the plant is helpless against the assault. Its close relatives in the grove, however, can pick up the scent of tannin in the air, and they respond by kicking their tannin production into high gear, whether they’re getting eaten at the moment or not. This way, when the first tree gets too toxic even for a giraffe, the animal will move on to the next tree and find that it’s already just as toxic as the first. Of course, now the giraffes have developed the trait of eating the trees from downwind up, so the arms race, it appears, is not over yet.
5. Set Fire to Themselves
The term “burning bush” is a loaded phrase, coming as it does from the Bible. In Genesis, the burning bush was God’s way of saying hello to Moses for the first time, and in the story, Moses was so impressed with what he saw that he had to take off his sandals, change his job from shepherd to high priest, and eventually get himself circumcised. Given that he already lived in an area with a bush that routinely sets itself on fire, one wonders what was so different about this one.
Throughout Europe, North Africa, and the western bits of Asia, there lives a single species of the genus Dictamnus. Late every spring, this plant starts leaking a sticky, oily resin all over its leaves and stem that makes it shine in the sunlight and gives it a faintly lemony scent. The plant is acrid to eat, so nothing does, and the oils it’s covered itself with protect it from most insects. Those oils also contain petrochemicals, and in the hot summer months, the whole bush is liable to burst into flames at the slightest provocation. It isn’t clear exactly why the bush does this, but it does have a lovely purple pyramid of blossoms in the spring, so it’s famous for home gardens. If you’re thinking about getting one, you might want to plant it away from any overhang and make sure your fire insurance is paid up.
6. Set Fire to Other Plants
Few words are as alarming to forestry officials as “fire.” Every year, forest fires destroy over 7 million acres of land (and over 2,500 structures) just in the United States. Countries that have developed economically to the point of caring about preserving their forests annually spend billions of dollars trying to prevent a fire from sweeping away in a week the natural heritage that took years to grow. So it’s a little annoying when a tree like a eucalyptus comes along and starts a fire itself.
Eucalyptus trees, which are endemic to Australia but grow almost everywhere else in the world now, grew up in the proverbial lousy neighborhood. To fight off competition from other plants, they’ve evolved the trick of oozing highly flammable oils from their leaves and trunks into the surrounding soil. This oil builds up for years until a grove of eucalyptus trees will be sitting on top of a huge incendiary bomb. When the smallest spark contacts the fumes from this, the resulting fire scours the landscape, killing every sapling, blade of grass, and other potential rivals. The eucalyptus itself almost always comes through okay – the living part of the trunk is deep inside the bark, so after a fire, they sprout new foliage and enjoy the wide-open, the utterly decimated landscape they have to themselves.
If there’s one thing that plants do well, it’s holding still. Even the walking palm, above, doesn’t walk, so much as slowly drift a bit over the years. If there’s any verb that doesn’t ever apply to a plant, it’s fly. But that’s precisely what the Javan cucumber has learned to do, or at least its seeds have.
Despite its name, the Javan cucumber is a creeper vine, related to the pumpkin, that climbs to the top of established tall trees in the Indonesian rainforest. When it’s time to breed, the cucumber drops seeds from as high up as possible to let them drift in the wind to a new home. Lots of other plants do this too, but the cucumber’s seeds beat them all by growing a wing-shaped membrane that’s as thin as a human eyelash, but large and strong enough to provide lift across the entire surface. The seeds look like stealth bombers, but better – wing-shaped craft have stability problems, which the cucumber overcomes in such a complicated way that we’re just going to dump a quote right here:
“[W]ithout automatic stabilizers, ‘flying wing’ aircraft are difficult to control. The Alsomitra macrocarpa fruit, however, has overcome this design weakness by having a center of gravity located close to (but in front of) the aerodynamic center of the wing due to the swept planform. At the same time, elastic deformation of the wing provides a twisted washout and dihedral, which helps it fly in a straight path and prevents ‘spiral instability’”
8. Hunt Other Plants
Plants are what are known as “autotrophs,” which means they can make their food out of sunlight and water. That’s unlike us “heterotrophs,” who need to eat food that’s already been made by either a plant or an animal body. This has given plants a friendly, harmless aspect that lies at odds with the image of a, for instance, slithering snake hunting through the undergrowth for a victim.
Enter the dodder vine, a.k.a. “strangleweed.” This parasitic vine doesn’t go to the trouble of putting down roots or growing leaves it doesn’t collect sunlight at all – and instead hunts other plants like a vampire. A vampire, as when it reaches your tomato plants it wraps around the stem and injects feeding pods that suck out all the juices. For creepy bonus points, the dodder shows an uncanny sense of direction when seeking out its victims. This it does by smelling them, and then growing in their path until contact is made. The dodder even can discriminate between targets; one study found that the vines almost always went after nearby tomatoes, but were put off by wheat.
9. Grow as Big as a Housing Development
Right in the middle of Utah, just south of Interstate 70 and about a mile or so from FishLake, there’s a small forest of trees with white trunks and bushy yellow foliage. As you move through this grove, it might eventually strike you as odd that the environment is so monotonous. Only one type of tree grows in this patch, which covers more than 100 acres, and everywhere you look there are just more quaking aspen trees. There’s just one tree, period. It’s a male aspen tree called Pando, and every one of the 47,000 trunks in the forest is a genetic clone of all the others. Because each shot is connected to a shared root system that crisscrosses the entire area, scientists regard the whole forest as being just a single, unbelievably large organism.
Nobody knows how or why Pando got started, but it’s known that conditions in Utah aren’t ideal for trees of this species to fertilize each other and successfully drop seeds, so it’s believed that the original colonist in this area just gave up on doing that. Today, Pando doesn’t bother trying to mate with other aspens in the area (which have gotten pretty scarce since the last ice age) and sends out its roots in all directions instead. At intervals along this root system, the grove sends up vertical shoots that can get up to 100 feet tall and live for centuries. When an individual shoot dies, it falls and fertilizes the soil, where another shoot will go up in the sunlight. Together, it’s estimated that this single organism weighs 6,600 metric tons, which is over 30 times heavier than a blue whale.
10. Live Forever
When we said above that nobody knows when Pando started, it isn’t because scientists haven’t tried to calculate its age; it’s because the tree’s age defies standard dating methods. Tree rings can only give the ages of individual shoots, which tops out at a couple of hundred years. Analysis of the root system suggests maybe 80,000 years, based on complicated science stuff, but some papers suggest that – because male trees live longer than females, and trees at Pando’s altitude (almost 2 miles above sea level) grow very slowly – the thing might be as much as 1 million years old. In theory, it could just keep growing forever, as the name Pando (Latin for “I spread”) suggests.
Pando isn’t the only super-old plant out there. These things are everywhere. There’s a colony of seagrass in the Mediterranean Sea that may be up to 200,000 years old, a group of creosote bushes in the Mojave Desert that seems to be 12,000 years old, and some plants in Tasmania that have a Pando-like colony that’s at least 40,000 years old. Even some seeds have gotten into the immortality race – a Judean date palm is currently growing in Israel from a seed that was lying around in the dirt for 2,000 years, roughly the time when the whole species went extinct. Between that and the colonial monsters like Pando, it seems some plants might be the Highlander.