Carnivorous Plants of New Caledonia

Laurent Legendre

University of Reims • France

New Caledonia is a small French territory located in the southern pacific ocean, 1500 km east of the Australian coast. It comprises a large number of tropical islands, but only the main one (called "la grande terre" over there) hosts carnivorous plants. More precisely, most carnivorous plants thrive in the southern tip of this island, in or around a large bog called "la plaine des lacs". Five taxa have been described: Nepenthes vieillardii, Drosera neocaledonica, Utricularia uliginosa, U. gibba and U. novae-zelandiae. Even though I was unable to witness the presence of the latter two Utricularia species or confirm their existence with the specimens stored at the herbarium in Noumea (capital city) or with the ones local botanists showed me, I was lucky enough to make several interesting observations on the three other carnivorous taxa. These observations stem from the visit of several hundreds of stations of each species three years in a row, each time around Christmas eve, in the middle of the summer, just before the start of the rain season.

N. vieillardii grows from sea level up to an elevation of 500 m. It favors open, sunny and well drained areas. It clearly benefits from the passage of cyclones, mining activity, road works and deforestation thanks to its carnivorous habit and its tendrils which do not allow it to climb on the surrounding vegetation but rather attach to it so that its liana do not break off under high wind or rain. Under sunny conditions, the plants bloom extensively, and develop light green and thin leaf blades, each of which produce a pitcher. The slightest shade will, however, slow growth and force the plants to stop flowering. Such plants will produce leaves that are 4 to 5 times longer, dark green, with thick leaf blades and no pitcher. This Nepenthes species is a case study for carnivorous plants enthusiasts as it develops 4 types of easily distinguishable pitchers: juvenile, lower, intermediate and higher. The pitchers exhibit a large color variation. Even though lower or older pitchers are always more red than higher or younger ones, it has become clear to me that different clones thrive on this island. Plants on the west coast (Mont Koghi) are all in the greens and reds while the pitchers of some plants on the southern locations (port Boise) are dark purple or all green with a black peristome, and plants on the east coast (Prony) have yellow-brown pitchers. It has also become apparent to me that, on the west coast, some plants only have all green pitchers while some see their pitchers go from green to red as they age or when they are located lower on the branch. Even though both populations often live at the same spot, no intermediate coloration can be seen, red plants are always more numerous and the presence of sun or shade does not seem to influence coloration.

But what is more intriguing is that the flowers of these plants also exhibit color variations. Male and female flowers can indeed be either green or red independently of the color of the pitchers. While dissecting some pitchers, I discovered that lower pitchers eat more creeping insects while higher pitchers preferably catch flying ones. Many live mosquito larvae could be seen floating in the pitcher fluid of lower and sometimes intermediate pitchers. A still unknown solitary large caterpillar with funny-looking antennas was also found to be living at the bottom of the fluid of the lower/intermediate pitchers.

The base of the stems of this Nepenthes species is visibly swollen all the way down to 10 cm below the ground and may serve as a water storage organ to survive through the dry season, a period during which the plants stop growing This rest period is also observed when the plants are cultivated all year long under warm and humid conditions. In cultivation, the top portion (ca. 10 cm) of the root only starts to thicken six months after seed germination.

D. neocaledonica is endemic to New Caledonia. Contrary to N. vieillardii, it displays no color or shape variation. It grows at elevations comprised between 100 and 500 m close to fresh water lakes and thus may be covered by water during the rainy season and stay bone-dry during the dry season. It prefers flat, sunny places and benefits from seasonal fires that clear its habitat from the bog weed Xyris pancheri. Even though many seedlings could be seen, the germination of seeds seems to be a problem in cultivation. It, however, propagates well via leaf cuttings.

U. uliginosa is usually found below the water surface (even at more than one meter below the water surface) and sometimes at the water edge. Flowers will not open unless they are above the water. They display a large panel of color variation from pure white to pink and blue. These color differences are retained under cultivation. The leaves are lanceolate and vary in length from a couple millimeters all the way up to 10 cm, a character which is lost under cultivation. I still do not know which factor controls the final size of the leaves. These will be whiter in full sun and greener in shaded areas. Some of the longest leaves form segments at the junction of which new leaves or flower stems may develop. The high leaf variation of this species as well as the fact that entire clumps can be unearthed and cleaned during heavy rain falls is, in my opinion, the origin of many misidentifications on New Caledonian Utricularia.

Even though carnivorous plants are common in New Caledonia, the future of all Drosera and Utricularia is threatened by the construction of a chemical plant to treat Nickel right at the center of this unique bog where most of them live. Let us hope that many clones will soon go into cultivation to preserve the rich genetic diversity present on this island.