Bracken ferns are a true success story if there ever was one. They occur in temperate and subtropical regions of every continent on the planet except for Antarctica. They very well may be one of the most widely distributed ferns on the planet. In late spring, their unmistakable fiddle heads poke up out of the soil like some sort of alien life-form and quickly unfurl into a giant, beautiful frond.
Known scientifically as Pteridium aquilinum, some authors treat all common bracken fern as a single species. Others feel that the group should be broken up into something like 10 different species. That will be a debate for another day. The fact of the matter is, bracken are very robust plants. As long as they can get enough light, bracken can handle a wide variety of habitat conditions. They thrive on human disturbance and thus are considered rather weedy or even invasive in many habitats.
With ambling rhizomes these plants can rapidly spread to saturate open habitats. Large populations are often referred to as bracken barrens. Their establishment and persistence is aided by the production of allelopathic chemicals, which can limit the establishment of other plants. This is especially true following fires. However, where forests are sparse, dense stands of bracken can actually provide a shaded haven for woodland herbs that would otherwise not be able to establish.
Bracken is not only toxic to plants, it is also highly toxic to animals. Bracken produces hydrogen cyanide when young fronds are damaged, quickly poisoning whatever may be munching on the frond. It also contains chemicals that cause uncontrollable rapid molting in insects, leading to a quick demise for any bug unlucky to have fed upon this fern. They also produce a chemcial known as ptaquiloside, which is highly carcinogenic in mammals.
With ample defenses and a hardy disposition, it is easy to see why these ferns are so successful. Coming across a large patch of these plants is, to me, a beautiful sight. It is the ultimate irony that we continue to create the very conditions that cause them rise to invasive status. If anything, they stand as a reminder that we humans are simply part of a greater ecological system, not masters of it.