Forward by David Fefferman: Do I have a treat for you! Our last bogging adventure post was so much fun that we decided to dive back into carnivorous plants in natural habitats. Today, I’m posting on behalf of Alvin Liu and Daniel DiPietro who manage CarnivorousJourney.com and are working on a book about Pinelands Drosera. These gents take their carnivorous plant hobby to the next level, and go on bogging adventures where they document wild plants and native habitats. This article is a teaser of great things to come, so keep a lookout for their tentatively-titled book Drosera of Southern New Jersey! Without further ado, here are Alvin and Daniel’s observations from Winter Dormancy in the New Jersey Pinelands:
Winter dormancy in bogs is not a topic that is discussed often, especially in the context of temperate carnivorous plants. For the most part, this makes sense; in the Southeast US, where Sarracenia are mostly found, temperatures seldom drop below freezing, so carnivorous plant habitat appears relatively boring during winter. Dormant rhizomes and browning leaves from the previous season’s growth are hardly photogenic, after all.
However, in latitudes where temperatures can regularly dip below freezing, carnivorous plant bog habitats can become truly fascinating places to visit in winter (and somewhat hazardous if you’re not careful, too!) One such example is the New Jersey Pinelands: a coastal, sandy swath of pitch pine forest that spans some 1.1 million acres over 7 counties of southern New Jersey, dotted with prime carnivorous plant habitat in the form of freshwater bogs and lakes. The NJ Pinelands host some of the densest concentrations of carnivorous plants on the East Coast, including Sarracenia purpurea, three species (and two natural hybrids) of Drosera, and numerous Utricularia.
Sarracenia purpurea is the only Sarracenia species native to New Jersey. It is also the most widely distributed, found all along the North American east coast from Georgia to northern Canada, although it only occurs in isolated patches of suitable habitat. Its squat, shapely pitchers are characteristic features of carnivorous plant habitat in the NJ Pinelands. This is particularly true in winter, since the pitchers of S. purpurea can remain intact for two years; dormant plants dot the habitat with splashes of color even as most of the other bog vegetation has died back.
S. purpurea tolerates freezing exceptionally well during dormancy. Plants can often be observed partially or fully submerged during the winter, frozen in solid blocks of ice. The foliage darkens to a deep red or maroon as temperatures drop – it is at this time that one can truly appreciate the meaning of the plant’s specific epithet purpurea (Latin for “purple”).
The NJ Pinelands represent a region where the ranges of the northern subspecies S. purpurea ssp. purpurea and the southern subspecies S. purpurea ssp. venosa overlap. Thus, many of the plants are intergrades that exhibit features of both – for example, pitchers that are squatter than those typically expected of the northern subspecies, but more glabrous (lacking hair/fuzz) than those of the southern subspecies.
Temperate Drosera undergo more dramatic changes during winter. They exhibit predictive dormancy, which is triggered by lower temperatures and the decreasing photoperiod during late autumn. At this time, the plants cease growth for the year and prepare for the onset of winter. In New Jersey, dormancy for Drosera, along with most of the other bog flora, begins around late October to November. Growth resumes in late April to May once temperatures remain consistently above freezing.
The dormancy process for Pinelands Drosera begins with the termination of all new growth; with no leaves to serve as replacements, existing leaves will gradually blacken from the tip downward, ultimately accumulating in a tangled black skirt around the base of the plant. The growth point itself develops a protective structure known as a hibernaculum, which is composed of modified, scale-like leaves wrapped in a tight, protective sheath around the growth point.
Hibernacula of D. intermedia and D. rotundifolia are not as tightly arranged as those of D. filiformis and tend to be much smaller. Rather than forming a singular, tight bud like D. filiformis, the hibernacula of D. intermedia and D. rotundifolia are composed of looser, modified leaves. They are mostly similar in color to the hibernacula of D. filiformis, occurring in shades ranging from green to golden-tan to reddish-brown. They can be extremely difficult to locate if flower stalks from the previous growing season are not present. Decaying stumps in open, sunny cedar bogs in the Pinelands are often dotted with D. intermedia and D. rotundifolia hibernacula, which may be found nestled among the remnants of their growth from the summer.
Drosera hibernacula are easily capable of surviving deep freezes provided that they are not subjected to desiccation or repeated freeze-thaw cycles. The hibernacula are often hidden in mats of frozen Sphagnum, with only the remnants of the previous season’s flower stalks visible to indicate that dormant plants are present. The Sphagnum mats provide additional insulation against desiccating winds. Drosera hibernacula may also inadvertently derive some benefit from the moss’s thermoregulatory properties, as the mats tend to remain frozen even as daily temperatures may fluctuate above and below freezing point. The Sphagnum itself, when situated above the waterline, remains in a mostly dehydrated state for most of winter. Ice will commonly crystallize around the moss heads and give the moss a stiff, brittle characteristic.