Specimen of the Month: "Crane-Berry"

I slipped into a local bog one evening last week, while the sunshine still stuck around long enough to hamper the autumn chill. I arrived with intent, but dismissed that and the encroaching darkness for a bit to take a look at some cotton grass momentarily bowing in the wind. Sitting on a clump of moss, I changed out my hiking boots for rain boots, then plunged into the bog, taking long, careful strides. I didn't want to let the cold water into my boots, but I also didn't want to overlook the shiny red pearls that I came to find. 

Cranberries (Vaccinium macrocarpon) produce the tart treat often associated with this time of year. The market supply of edible cranberries now comes from commercial sources in states like Wisconsin, Massachusetts, and New Jersey, but until the mid-1800's, people had to venture into natural habitats to find them. The red fruits of cranberries are conspicuous enough, and the dainty pink flowers resembling cranes are easily recognizable early in the summer. Still, the plant itself is small and delicate. One should probably dedicate a good portion of the day--not simply an hour after the work day--to investigate what lies within the sphagnum hummocks of our local bogs. 

The fruits of cranberries dot sphagnum hummocks
with shiny red during a cold October evening.

Cranberry plants are low-growing perennials with small, ovular leaves that can remain green throughout the year. The cranberry is not a real berry at all. Rather, cranberry plants are actually "epigynous," having false berries. They are the product of a 16-month growth cycle that begins with the initiation of a flower bud. Changing day length will trigger these buds, sometime during July, to enter dormancy. This then lasts until the following spring when buds are exposed to enough “chilling hours” of 32 to 45 degrees. Flowers grow into the characteristic shape of a crane's head and beak, which inspired the name "crane-berry" that was eventually modified to "cranberry." During flowering mid-summer, native bees help to pollinate. Bumble bee species are the most effective at this as they buzz pollinate--using their flight muscles to literally shake pollen from within the flowers. Others, like leaf cutter and mason bee species, use their legs to drum on the flower to release pollen. Thanks to these pollinators, cranberries ripen by mid-autumn and support various animals who enjoy the fruits.

Although small, the bright pink cranberry flowers stick out against various
green sedges and shrubby plants in a bog. 

The Museum's only herbarium specimen of a cranberry plant was collected over forty years ago during July flowering. In 1975, this particular specimen grew in an area outside of Drummond noted as a "large floating bog on [an] open lake...creeping over sphagnum, [on the] edge of water." I have yet to visit this site--the density of wetlands like open bogs and fens here hasn't required that I do much more than take a short walk down the road from my home. 

Herbarium specimens and their associated information help to capture a
snapshot of plant life in a particular time and place. 

Bogs are not confined to northern Wisconsin, but often form in the glacial depressions left many years ago when glaciers altered our landscape. The thick distribution of cranberry plants here directly reflects the abundance of its habitat. Still, I find it quite miraculous that wild cranberries and their bog habitat have sustained, as they are dependent on very particular conditions that are not easily mimicked. Without such a unique wetland habitat, we would (nor will) not have such unique plants as cotton grass, charismatic sundews and pitcher plants, or the wonderful cranberry.