A Circumboreal Butterwort

The name "butterwort" may sound quite silly to most but those who have seen one in person can attest to the fact that there is nothing silly about the group of plants this name has been given to. Hailing from the genus Pinguicula, my favorite butterwort is Pinguicula vulgaris.

Referred to as the common butterwort, this species is sometimes hard to find if you live in North America. It has a circumboreal distribution and seems to be much more common in Europe and parts of Russia. Like all butterworts, P. vulgaris is a carnivore, though at first glance this may not be very obvious. The fleshy rosette of leaves are covered in mucilaginous glands that trap hapless insects. The leaves will sometimes roll in along the edge to pool the digestive juices around their prey.

Unlike more familiar carnivorous plants that can be found in acidic soils, P. vulgaris is a calciphile. It is most often encountered in fens, alvars, and other areas with limestone bedrock and alkaline waters. These types of habitats pose a different set of challenges for plants when it comes to obtaining nutrients. Phosphorus becomes bound to sediments in these alkaline conditions and research has shown that most butterworts respond best to supplemental phosphorus additions, though other nutrients like nitrogen are absorbed from prey as well.

If their carnivorous habits weren't interesting enough, the flowers of P. vulgaris (and all butterworts for that matter) are gorgeous. Sitting atop long stalks, the spurred blooms are a deep shade of violet. The nectar spur suggests that this species is pollinated by either long tongued bees or butterflies. Either way, they are presented well above the sticky leaves to reduce the chances of the plant eating the insects it needs for pollination.

Like all plants in the northern hemisphere, P. vulgaris needs to deal with winter. As temperatures and light levels begin to drop, P. vulgaris reverts to a cluster of buds called a hibernaculum. It has no roots and can easily blow around if exposed. This may serve to transport plants into new locations. Due to rampant habitat destruction, this plant is quite vulnerable in North America and threatened or endangered in many parts of its range.

Further Reading:
http://plants.usda.gov/core/profile?symbol=PIVU

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1984.tb04105.x/abstract

http://mnfi.anr.msu.edu/abstracts/botany/Pinguicula_vulgaris.pdf

http://www.snh.gov.uk/docs/B823176.pdf