Home Environment Encyclopedia of Cultivated Plants: From Acacia to Zinnia
A carnivorous plant, the butterwort is in the genus Pinguicula, Latin for “little greasy one.” The name derives from the greasy texture of the leaves. Some people have likened this texture to the slipperiness of melted butter, a circumstance that gave rise to the name butterwort. Before scientists understood its carnivorous habit, the people of Northern Europe rubbed butterwort leaves on the wounds of cattle. This treatment was effective because butterwort leaves produce an antiseptic secretion. Others used the leaves to curdle goat’s milk into cheese. Norwegians used the leaves to make a thick milk. One tradition hold that a girl who puts butter- wort leaves beneath her pillow will dream of her future husband.
No one apparently appreciated that the butterwort was a carnivore until the 19th century. In the early 1870s, W. Marshall—his first name and occupation may be lost to history—noticed a butterwort whose leaves were covered with insects. He informed British naturalist Charles Darwin of this find. In 1875,
Darwin amassed the evidence that the butterwort and several other species of plants were carnivores. Journalists and religious leaders mocked Darwin for this conclusion. Objections to the idea that plants may be carnivores go back at least to the 18th century, when Swedish naturalist Carl Linnaeus took up the crusade against this heresy.
For more than a century, the carnivorous habit of the butterwort has fascinated scientists. The leaves appear unremarkable to the casual observer, but close inspection reveals that glands cover them. Many of the glands support short hairs atop, which are globules of mucilage. Sunlight makes the mucilage sparkle, and this effect may attract insects. Moreover, the leaves emit an earthy aroma, which may attract insects. It is also possible that insects perceive the leaves as landing pads. Whatever the reason, an insect that alights on a leaf finds itself stuck in mucilage, which is an adhesive. The butterwort therefore functions as flypaper, though it has the capacity to digest insects whereas flypaper is a passive trap. As an insect struggles to free itself, it contacts other hairs and becomes entangled in a film of mucilage. An insect may struggle so violently that it loses a leg, but its efforts are usually futile. Covered in mucilage, an insect drowns or suffocates, though hours may elapse before death conquers the suffering arthropod.
As soon as an insect is caught, the sessile glands, which are inactive when a leaf is bereft of prey, begin to secrete digestive juices, which contain acids and enzymes and which liquefy the innards of an insect. The glands produce copious amounts of these juices, and they might run off a leaf but for the fact that the leaves of temperate species curl to prevent the loss of juices. Curiously, the leaves of tropical bladderworts do not move. In hours or at most days, the digestive juices accomplish their task. The sessile glands absorb the liquefied insect, leaving only the exoskeleton, which may remain adhered to the mucilage. The exoskeleton may break apart, or wind or rain may remove it. Because butterwort leaves are small, they trap tiny insects: gnats, springtails, and fruit flies. A springtail may succumb after contacting just two hairs on a leaf. Large, strong insects may break free, though butterworts have captured flies and craneflies. One specimen even captured a praying mantis.
Diversity of Species
Butterworts inhabit a range of ecosystems. They grow as far north as the Arctic Circle and may be found in North America, Central and South America, Europe, Asia, and Africa. Species native to the tropics produce flowers as striking as those of orchids and African violets. Flowering in spring, they yield one bloom per stalk. In the arid lands of Mexico, they grow alongside cacti. In parts of the Northern Hemisphere, they may be found with the sundew and pitcher plant. Tropical but- terworts are most diverse in Mexico, Central America, and the Caribbean. More species of butterwort grow in Mexico than anywhere else. In the dry season, tropical butterworts are not carnivorous, producing leaves that do not capture insects. Some species grow at elevation, enduring chilly nights during winter and hot, wet summers. Flowering over several months, the tropical Pinguicula morenesis blooms twice per year, issuing forth pink or white flowers. The plant flowers in winter and spring and again in late summer. Pinguicula esseriana, despite its tropical habit, tolerates frost. Pinguicula heterophylla and Pinguicula macro- phylla are dormant during the dry season. Pinguicula filifolia, native to western Cuba, grows in sandy soil near lagoons, yielding white, blue, purple, or lilac flowers. Pinguicula albido, Pinguicula jackii, and Pinguicula lignicola also inhabit Cuba. An epiphyte Pinguicula lignicola grows in trees and bushes. Pinguicula cladophila is native to Haiti.
Temperate butterworts survive cold winters by dying down to buds known as hibernacula, meaning “hibernate.” They may lose their roots during winter, allowing flowing water to move them. The movement of temperate butterworts in this way may account for their diverse geography. Dormant in winter, temperate butterworts resume growth in spring. They flower in spring, yielding purple, violet, or white flowers. Growing in wet, acidic peat in North America and Europe, they may be found with ferns. Along with the pitcher plant, temperate butterworts inhabit rocky soil near the Great Lakes. Some temperate species grow in neutral or alkaline soil. They do well in full sunlight, though planted near grasses and ferns, the latter will shade them.
The temperate butterwort Pinguicula vulgaris is renowned as the species Darwin studied. It grows in North America, Europe, and Northern Asia. Preferring rocky soil, it grows near lakes in acidic or basic soil. Pinguicula macraceras inhabits the western United States, Canada, Japan, and Russia. One subspecies may be found with the Darlingtonia pitcher plant in the Pacific Northwest. Pinguicula grandiflora inhabits the hilly regions of Ireland, France, Switzerland, and Spain. Pinguicula alpina grows in the mountains of Europe and in Scandinavia and Scotland. The rare Pinguicula remosa is an indigene of northern Japan. Nearly extinct in the wild, only two colonies remain. Cultivation may be the only way of perpetuating this species. Perhaps because it is so rare, the Japanese have memorialized it on a postage stamp. Pinguicula villosa inhabits the Arctic regions of Asia, Northern Europe, and North America.
Some temperate species, dubbed “warm temperate butterworts” by one gardener, are accustomed to warm weather, surviving in the subtropics. They tolerate frost, but a hard freeze may kill them. Preferring wet, acidic soil, several of these species inhabit the American Southeast with the pitcher plant, the sundew, Venus’s Fly Trap, and the bladderwort. A bog plant, Pinguicula coerulea, known as the violet butterwort, inhabits the southeastern United States from North Carolina to Florida. Pinguicula primuliflora and Pinguicula plenifolia grow from the Florida panhandle to Louisiana. Growing in wet peat or sphagnum, Pinguicula primuli- flora inhabits land near streams and ponds. Native to the American South, Pinguicula pumila grows from the Carolinas south to Florida and west to Texas. Pinguicula lusitanica grows in wet peat in Britain, Spain, and northwestern Africa.
Temperate butterworts prefer a soil of two parts peat, one part sand, and one part perlite. Warm temperate species should be given a soil of equal parts peat and sand. Tropical butterworts like a mixture of sand, perlite, vermiculite, and peat. To these ingredients one may add dolomite, gypsum, lava rock, and pumice. Temperate and warm temperate plants may be potted with the pot placed in a saucer of water. In addition to this method of watering, the gardener should wet the soil by pouring a container of water on it. Cool water is best. Tropical butterworts should also receive water from a saucer and a container in summer and autumn, but they should have less water in winter. Pinguicula gypsicola, Pinguicula heterophylla, and Pinguicula macrophylla must have a dry soil in winter. Cuban species should be kept wet year-round with slightly less water in winter. All butterworts relish abundant sunshine. Pinguicula morenensis is among the most popular species in cultivation and may be grown by a sunny window, in a greenhouse, or in a terrarium. Warm-temperate butterworts do well in a greenhouse with or without heat. In cultivation, Pinguicula lusitanica may be found in greenhouses with or without heat, terrariums, a sunny window, or a bog garden outdoors. Most temperate plants do poorly indoors unless kept in a greenhouse. The gardener may feed indoor plants fruit flies, small ants, and dried insects. Butterworts bereft of insects may receive fertilizer. Temperate species may be sprayed periodically with dilute fertilizer. Tropical butterworts should be sprayed twice per month with fertilizer at one- quarter strength. The gardener should confine fertilizer to the leaves because it may discolor flowers.
Barthlott, Wilhelm, Stefan Porembski, Ruediger Seine, and Inge Theisen. The Curious World of Carnivorous Plants: A Comprehensive Guide to Their Biology and Cultivation. Portland, OR: Timber Press, 2007.
Camilleri, Tony. Carnivorous Plants. Sydney: Kangaroo Press, 1998.
D’Amato, Peter. The Savage Garden: Cultivating Carnivorous Plants. Berkeley, CA: Ten Speed Press, 1998.
Lecoufle, Marcel. Carnivorous Plants: Care and Cultivation. London: Blandford, 1989.
Pietropaolo, James, and Patricia Pietropaolo. Carnivorous Plants of the World. Portland, OR: Timber Press, 1986.
Rice, Barry A. Growing Carnivorous Plants. Portland, OR: Timber Press, 2006. Schnell, Donald E. Carnivorous Plants of the United States and Canada. Winston- Salem, NC: John F. Blair, 1976.
Slack, Adrian. Carnivorous Plants. Cambridge, MA: MIT Press, 1979.
Temple, Paul. Carnivorous Plants. London: Royal Horticultural Society, 1993.
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