By Agustin Franco, Ph.D., Sydney, N.S.W., Australia
This article is dedicated to those who spend their lives growing this beautiful, but unusual carnivorous plant.
Cephalotus follicularis (labillardiere, 1806), commonly known as the West Australian pitcher plant, Albany pitcher plant or Australian ground pitcher, is the only species of the genus Cephalotus. The word “Cephalotus” comes from the greek “kephalotos” meaning "headed", which refers to the filaments of the stamens. The word “follicularis” refers to follicles or small sacs, which describes the shape of the carnivorous pitchers [Fig. 1].
Fig 1. Cephalotus follicularis in the wild. (Photo courtesy of Mrs. Pat Johns, Wildflowers Society of Western Australia)
The plant’s original habitat is Southwestern Australia, its range of distribution is about a 400 km strip from regional Albany to Eusselton (Western Australia). This plant naturally grows in a meso-mediterranean climate characterized by cool and wet winters followed by hot summers. However, the temperature fluctuations in this area almost never reach below 5ºC in winter and hardly exceed 25ºC in summer, but it can rise up to 40ºC (Cheers, 1992)
As most carnivorous plants, it prefers a humid environment and loves to grow amongst grasses and shrubs. In other words, it prefers shaded areas. If the plant grows under direct sunlight, it accumulates anthocyanin, a pigment responsible for the red colouration of the pitchers. In nature, Cephalotus mainly grows in a mixture of sand, grass, and peat while dieting on mainly crawling insects such as ants.
Cephalotus follicularis has two types of leaves: non-carnivorous and carnivorous. The non-carnivorous leaves are usually spear-shaped; even though, during the winter, round non-carnivorous leaves are produced. The carnivorous leaf or pitcher is one of nature’s masterpieces. It has a peristome or mouth filled with inner pointing teeth. The lid has translucent segments alternating with darker ones and has three functions: The first one involves attracting insects by showing the reflection of the water at the bottom of the pitcher through its semi-transparent segments. The second function is to keep the rain-water out of the pitcher; and the third function is to maintain the internal humidity in hot days, by superimposing over the mouth of the pitcher. As the levels of humidity return to normal, the lid would move back to its original position.
The outer walls of the pitcher have a T-shaped central rib with hairs along the sides and two lateral ridges also with hairs that serve as ladders for the insects attracted by the sweet nectar contained within the pitcher. The mouth or peristome has around 24 inward pointing teeth (Lloyd, 1976) . Mature pitchers have these teeth of up to 4mm long in the center of the mouth, while other varieties with similar size pitcher have smaller teeth of up to 2.5 mm long. The inner wall of the pitcher is coated with wax creating a very slippery surface. The inward pointing teeth, in combination with the slippery inner surface of the pitcher, makes any insect’s attempt to escape futile. The lid also varies in shape. While some Cephalotus have an inverted spoon-shaped lid, others have a half shell-shaped lid. The pitcher is filled with bacteria and digestive enzymes, which will break down and absorb proteins and other nutrients from the prey. (Lowrie, 1998).
There are some variations in the shape of the pitcher as well. The most common pitcher type has an elliptical-shaped mouth. There is another variety with a very narrow and cylindrical mouth and a sausage-shaped pitcher. This variety of Cephalotus produce fairly long pitchers (up to 5 cm long) and wide non-carnivorous leaves (Phill Mann’s collection).
One of the most interesting topics amongst carnivorous plant growers is Cephalotus follicularis pitcher size. The “typical form” of Cephalotus follicularis pitcher size ranges from 1 cm (less than ½ inch) to 5 cm (1.96 inches) with an average of 2.5 cm (1 inch) in length (Lowrie, 1998) . However, several experts in the field do recognize that some plants of Cephalotus follicularis can have pitchers that measure more than 5 cm long, but they also imply that this event is very unusual (Cheers, 1992; Lecoufle, 1990; Lloyd, 1976) [Fig. 2].
Fig 2. Young Giant Cephalotus follicularis plant of unknown origins. The pitcher shown in the picture is next to a large size egg. Average size of a large egg (6.5cm). Average size of pitcher is 4.9 cm. (Photo courtesy of Mrs. Julie Jones, Ponsanooth, England)
Measurements of Cephalotus pitcher size have generally been taken from the bottom of the pitcher to the uppermost portion of the lid. For practical purposes, in this article, measurements were taken from the bottom of the pitcher to the mouth, since the lid can move up and down, depending on the relative humidity levels. Final pitcher size was calculated based on object-size proportion.
In September 1986, an American carnivorous plant grower by the name of John Hummer, received about a half-dozen of mature plants from a pen pal in Adelaide-Australia named Stephen Beckwith. All had a nice maroon colouration and their pitchers were at least 5 cm (1.96 inches) in length that had over-wintered from the previous year’s growing season. The plants had been dormant and were starting their growing cycle once again. He distributed the plants to some of his colleagues and started growing the rest in a terrarium. Couple of years later, John Hummer obtained plants with pitchers around 6 cm (2.4 inches) in length and 2.5 cm (1 inch) in width. He has been propagating and distributing this plant all over the world [Fig. 3].
Fig 3. Cephalotus follicularis “Hummer’s Giant”. Size comparison with an American quarter. Average large pitcher size (5 cm) or 2 inches. (Photo courtesy of Mr. Jeff Mathesson, Rhode Island, U.S.A.)
Under artificially controlled conditions, this plant can reach up to 8 cm long (3 inches) (Bill Mclaughlin of the US botanical Gardens). John Hummer has established this plant as a cultivar, naming it Cephalotus follicularis “Hummer’s Giant”. He coined the name in April 3rd, 2000; even though this cultivar name has been used years prior this date (Hummer, 2000) .
Mr. Stephen Beckwith obtained the Hummer’s Giant clone from another cp grower by the name of Michael Ceple who used tissue culture to grow his collection of carnivorous plants, including Dionea, Darlingtonia, etc. Unfortunately, Michael Ceple passed away several years ago; therefore, the exact growing conditions, as well as, the region of Western Australia where this Hummer’s Giant clone was picked up from remains a mystery. (Stephen Beckwith, personal communication).
Hummer’s Giant growing conditions
Mr. Jeff Mathesson, a very successful Cephalotus grower, uses 2 parts peat moss to one part sand and one part perlite. The plant in Figure 3 grew under natural light, but with at least 75% humidity. He has attempted to use fluorescent lights, but he never had the same results as those obtained with natural sun light. When fluorescent light is used, the lights are on for at least 14 hours a day. He recommends dormancy to achieve maximum pitcher size. The clone Hummer’s Giant, according to him, is different from other large Cephalotus plants. The T-shaped ridge, which goes along the central portion of the pitcher, grows very wide and long early on during development.
Cephalotus follicularis ‘giant form or true giant’
A year after John Hummer had received his Hummer’s Giant, another well-known cp grower by the name of Harold Weiner introduced another giant variety form to Germany. This particular plant has pitchers that can reach over 8 cm long and it is often referred as the as “giant or true giant” [Fig 4].
Fig 4. “True giant” form of Cephalotus follicularis: Palmengarten, Frankfurt, Germany.
Top: Adult plants. Size comparison of the pitchers and the tree logs.
(photo by Andreas SieglerÓ, Lohr am Main, Germany)
Bottom: Young “true giant”.
(photo courtesy of Dr. Heilke Steinecke, Palmengarten)
Jan Schlauer, a cultivar registrar from ICPS (International Carnivorous Plant Society) contends that Harold Weiner may have had this clone many years before it was commercially available in Germany. Several attempts were made to contact Harold Weiner without success. He left Germany in the late 80’s and he is living in Mamba Village, Kenya, where he is directing a carnivorous plant botanical garden. Mr. Weiner, according to his former colleague and friend, Helmut Kibellis, never used tissue culture techniques to grow his plants.
Furthermore, Harold Weiner and John Hummer have never met and there is no evidence to suggest that either the “true giant” is the same as the Hummer’s Giant. Furthermore, empirical knowledge from many Cephalotus growers suggest that the “true giant” grows very slowly while the Hummer’s Giant grows like the “typical form” (Tony Paroubek, Martin Reiner, Jan Schlauer, and Charles E. Brewer, personal communication). Recent pictures shown at http://www.Cephalotus.info clearly shows the differences between Harold Weiner’s and John Hummer’s clones. The former has a relatively thin T-ventral rib and smaller size teeth than the latter.
Cephalotus follicularis “true giant” growing conditions
The medium used in Palmengarten, Germany, according to Dr. Hilke Steinecke, consists of a mixture of peat moss and sand in nearly the same proportions with some sphagnum moss placed under the soil and some on the soil surface. The medium is highly humid, but plants are not waterlogged. The plants grow with quicksilver vapor bulbs (600 Watts). The bulbs are switched on for 12 hours every day, all year round. Whenever the sun is out, the computer controlled lighting system is switched off. The time it takes for the plants to reach maximum size depends a lot on the local weather conditions. In Frankfurt, the weather is highly variable, so it is difficult to give an accurate amount of time. However, plants grown from cuttings may take 4-5 years to reach maximum size.
Why are there giant Cephalotus?
While there is no immediate answer as to why giant Cephalotus clones exist, many carnivorous plant growers believe that the so called “giant forms”, are due to excellent growing conditions of the “typical forms” which include optimal potting mixture, humidity, light, and temperature. These, in turn, will have a dramatic effect on pitcher size. This hypothesis is based on the fact that in many instances, as witnessed by some Cephalotus growers, the “giant forms” don’t develop full size and these are only up to 10% larger than the typical form. On the other hand, what is considered “typical form” of Cephalotus follicularis plants, can have pitchers up to 5 cm long or perhaps more, again if the conditions are optimal for their development [Fig 5].
Fig 5. Large Cephalotus follicularis plant. (Photo courtesy of Mr. Jeno Kapitany, Paradisia Nurseries, Victoria, Australia)
One important aspect is not being considered though; many believe that because Cephalotus follicularis is the only member of the genus Cephalotus, homogeneity in the genetic make up of these plants is obligatory. In other words, it is expected all plants to be the same or look the same. This statement without doubt is erroneous. There are variations in pitcher and lid shape, not to mention pitcher size within the same plant (polymorphism). As result, Cephalotus plants in Denmark, W.A. for example, are expected to have some minor genetic differences from those found in Albany, W.A. The presence of minor variations in a specific gene coding sequence, as well as variations in gene content, form part of a “gene pool”. Whether these differences are obvious to the eye or not is irrelevant, because genetic variation almost always exists within any plant or animal population. This hypothesis is supported by the fact that humans or Homo sapiens belong to one species, but yet there are different races within this species as well as small differences within one race. Doesn’t this mean we must look the same? : Obviously not.
The never-ending debate of environmental conditions vs. genetic make up applies to Cephalotus as well. Both play a role in the development of a plant.
There are plants with the predisposition to develop large pitchers, but if these are not in an environment that encourages optimal growth, these will never reach maximum size. On the other hand, a so called “typical form” plant might be subjected to optimal growing conditions for pitchers to reach maximum size, but if the parent plant only produces small pitchers up to 3 cm long, the next generation of pitchers from the same plant will be no more than 3 cm long (Mendelian genetics).
The existence of “giant forms” of Cephalotus may be nothing more than a man-made selection of clones that are predisposed to reach maximum size under ideal, but artificial growing conditions. As a matter of fact, tissue culture techniques to propagate plants have been performed at least since the late 1960’s. The propagation of seedlings and cuttings in vitro promotes the doubling, tripling, and even quadrupling of chromosomes in plant cells (Demoise, 1969) . This phenomenon is known as polyploidy. When plants have extra chromosomes, they usually have larger characters: larger fruits, flowers, and leaves. Furthermore, The use of alkaloid chemicals in horticulture such as colchicine, a known polyploidy inducer, naturally produced by a plant Colchicum autumnale or Autumn crocus, has been a common practice since the mid 1940’s to improve physical characteristics of plants (Dawe, 1998) . It is by no means implied that the origins of the “Hummer’s Giant” and the “true giant” are due to chromosome duplication or to exposure to polyploidy inducers. Scientific data is needed to confirm or discard the hypothesis of chromosomal duplication. It is, however, a very plausible explanation on how these giant clones arose, keeping in mind that the general consensus regarding Cephalotus follicularis pitcher size is that they are small and no larger than 5 cm (1.96 inches).
The growing conditions found in nature are limiting factors; therefore, the pitchers may never reach maximum size, due to the constant competition for nutrients by other plant and animal species co-inhabiting with Cephalotus such as Drosera hamiltonii. As a matter of fact, the development of plant carnivory may be the result of plant adaptation and evolution in relatively nutrient-poor soils, where the plant needs to use alternative sources of nourishment. There must be a fine balance between the energy spent and the energy acquired by a plant. In a nutrient deficient environment, a plant can not afford to spend much energy in developing large size pitchers. Perhaps this is why Cephalotus plants with pitchers larger than 5 cm in length are very difficult to find in the wild bush of Southwestern Australia, but it does not mean they don’t exist. It would be interesting to find out why some of these plants have a predisposition to develop large pitchers, while others don’t, when the presence of a large pitcher phenotype is apparently not needed for the survival of the species. After all, Cephalotus’s victims are generally very small in size. How many of these would a Cephalotus plant need to trap to satisfy their nutrient requirements, considering that each plant has usually more than one pitcher?. Obviously these questions will need further study.
I would like to thank all who contributed to the completion of this article: John Hummer, Jan Schlauer, John Mathesson, Hilke Steinecke, Julie Jones, Andreas Siegler, and Stephen Beckwith for useful information. Special thanks to Allen Lowrie, Gordon Cheers, and Mr. Charles E. Brewer for helpful discussions.
Cheers, G. 1992. A Guide to Carnivorous Plants of the World. Collins Angus Robertson, Sydney. 174 pp.
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Demoise, C.F., Partanen, C.R. 1969. Effects of subculturing and physical condition of medium on the nuclear behavior of a plant tissue culture. Amer. J. Bot. 56:147-152.
Hummer, J. 2000. Cephalotus "Hummer’s Giant". International Carnivorous Plant Society. 29:119-120.
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Lecoufle, M. 1990. Carnivorous Plants. Cassell Villiers House, London. 144 pp.
Lloyd, F.E. 1976. The Carnivorous plants. Dover Publications, Inc., New York. 354 pp.
Lowrie, A. 1998. Carnivorous plants of Australia. University of Western Australia Press, Nedlands. 285 pp.