Sundews in the Sand Dunes


Drosera filiformis, or the threadleaf sundew, tend to grow in sandy and wet areas on Long Island, usually near or around coastal plains ponds. They also surprisingly grow among the sand dunes of the south fork of Long Island. Some of these dunes can reach 80 feet high, and shift with the winds, marching steadily across the landscape. In these dunes, there are swales, and there is one that reaches down to the ground water table. This keeps the sandy soil consistently wet with fresh water, and cranberry, Vaccinium macrocarpon, and pitch pine trees, Pinus rigida, grow throughout this swale. Other interesting plants grow here as well, such as the bog orchids Rose Pogonia, Pogonia ophioglossoides, and the Grass Pink, Calopogon tuberosus. Then there are the carnivorous plants, the spoonleaf sundew Drosera intermedia, and of the most interest here, the threadleaf sundew, Drosera filiformis.
In the first photograph, we see a swath of Drosera filiformis, growing in nearly pure sand and exposed to continuous sunlight throughout the day. The second photograph shows a closer look at this population, and the sandy soil where it grows. The color of the plants appear to be a curious orange color, where Drosera filiformis are known as mostly green, or completely red, in the case of certain populations in Florida. For the third photograph, we have a detailed view of an individual plant from this population. With closer inspection, we see that its leaves are still green, but very much a yellow-green color. Perhaps because of the long-term continuous exposure to strong sunlight, the green color of the leaves of these plants, have shifted to become more yellow. The trapping tentacles are the typical red color, and when seen from an average viewing distance, it seems that the yellow tinge of the leaves, combined with the red tentacles, give the plants the pleasant orange hue we see here. This is observed at one specific spot in this dune swale location, the other Drosera filiformis nearby, being more typical in character. Other locations on Long Island can have plants with an orange tinge to their hue when exposed to strong sunlight, just never quite as brilliant as these particular plants in this little swath in the great dune swale.
The fourth photograph shows the flower of Drosera filiformis from this population, and the final photograph shows the flowers being pollinated by a bee-mimic hoverfly, perhaps a species of Sphaerophoria. The carnivorous traps seem precariously close to their flowers, yet when the hoverfly was observed, it went directly from flower to flower with focused purpose, and no distraction. There are other nearby locations where Drosera filiformis grow within sand dune swales, although this is the most brilliant of them all. Strange as it may seem, that surrounded by dry sand, with no visible fresh water, and with the salt-water of the sea mere hundreds of yards away, plants that are normally found around ponds can flourish with such great vigor and numbers. Though here they are, another wonderful surprise in the unusual and bizarre world of carnivorous plants.


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