Everyone knows that plants have evolved to protect themselves, but few appreciate just how cutthroat the things really are. They constantly plot and scheme to destroy competitors, often more fiercely than animals. Because plants are generally immobile, they must use more subtle methods.
Many plants contain toxins that ward off animals, such as coffee plants which developed caffeine as an insecticide. Some plants poison the ground around them to keep other plants away. Vines have been known to strangle and smother trees. Plants put out a variety of lures to trick animals into spreading their seeds, such as flowers or fruits.
To my mind, the dirtiest of all dirty tricks in the plant world is perpetrated by pine and eucalyptus trees.
It is well known that pine and eucalyptus trees are resistant to fire. Indeed, many species of pine require fires to open up their cones and release the seeds. Most other tree species are not as resistant, which is a fact the pines and eucalyptus use to cruel advantage.
Pine trees contain a highly flammable resin, and their needles burn particularly well. Eucalyptus oil is extremely flammable, and some trees have been observed to actually explode during severe fires. This is not an accident. These trees have evolved specifically to burn. That may sound odd, but it is a crushing advantage.
Recently burned forest puts a lot of nutrients into the soil. Plants will quickly try to move into the are, to take advantage of the soil and the access to light provided by the missing vegetation. However, these resources are easier to seize if one is already there. To do this, the pines and eucalyptus are both highly flammable and fire tolerant. They will build up a huge store of very burnable wood, over the years providing enough fuel for massive forest fires. When the fire does come, it will burns the resins and oils in the wood, creating fires hot enough to kill all other plants, but not quite hot enough to kill all the pine or eucalyptus trees. They will remain, having destroyed all of their competition. The fires also cause the seeds to emerge, and the seeds fall onto ground specifically prepared to be as welcoming as possible.
By using a literal scorched earth policy against other species, pine and eucalyptus trees have developed a compelling advantage. They are plotters of the worst sort.