The cobra plant is a herbaceous perennial consisting of a rhizome, with fibrous roots. Tubular pitcher leaves arise directly from the rhizome, forming a rosette. In this species, the hood of the pitcher is well developed to form a dome, with the pitcher opening facing downward. The pitcher lid is modified into a two-lobed, fishtail-shaped appendage projecting downward from the frontal edge of the opening. A peculiar feature of the plant is that the leaves twist about one half turn as they grow. As a result, the pitcher openings tend to face outward from the plant center. This conceivably provides wider coverage for prey acquisition. Based on my casual but numerous field observations, the direction of the twist is just about even between clockwise and counter-clockwise, though within a given individual the direction is fixed.***

In a typical natural habitat, a mature pitcher leaf stands between 40-60cm tall. Leaves reaching 100cm are found in some low-light conditions. Seen in the field, the overhanging hood of the pitcher leaf gives the impression of a deadly cobra poised to strike in imminent defense, hence the common name.  Other names for the plant include "cobra lily" and "California pitcher plant".

The distribution of cobra plants is limited to montane seeps in northern California and the coastal bogs along the adjacent western part of Oregon. The colonies are highly localized in characteristic marshy habitats often with fresh, running waters. 

OK - Habitat

Leaves of the cobra plant sprouting out in the thousands on grass-covered slopes in the mountain habitat -- with their cobra heads glowing in a golden hue -- offer a truly spectacular sight in nature.

Streams flowing through mountain meadow create an ideal habitat for this remarkable species of the pitcher plant family. Cold waters from the mountain springs rush through a mild mountain slope in a sparsely populated coniferous forest, forming a wide band of marshy surface along the water path. It is in such an exacting setup that the colonies of the cobra plants thrive. The plants' fondness for this particular setup is clearly seen / manifested in the astonishing similarity of many a montane habitat throughout their range.

Many cobra plant sites are also known to be located on or near serpentine rocks, providing continuous stream flowing through serpentine rock formations in the region. The soils in these habitats are poor in nutrition, providing a competitive advantage to the cobra plants possessing a carnivorous lifestyle.

Many populations are found in the montane habitats at an altitude of up to 2500m, although some vigorous stands of cobra plants can be seen a few feet above the sea level along the Oregon coast. The plants seem to be tolerant to this climatic variation (Juniper, et al. 1989).

Rondeau recognizes two kinds of primary habitats for Darlingtonia: A typical montane habitat is what is duly described as a seep, often with a moderate slope, having constant water flow on the soil surface. The plants also grow in what can be described as "Darlingtonia bogs", which are only found along the coastal plains in Oregon, with near-zero slope, but with external water input and drainage (Rondeau 1995).     

As for accompanying carnivorous plants, cobra plants are often found with Drosera rotundifolia (round-leaf sundew) in northern California and southwestern Oregon. There are some colonies in southern Oregon where Pinguicula macroceras ssp.nortensis (butterwort) grows extensively alongside Darlingtonia. 

In summer, the daytime temperature may reach 35 degrees Celsius in some localities. However, the running water where the root is submerged rarely exceeds mid-20 degrees Celsius on the same day. This constant supply of cold water from mountain springs seems essential for the healthy and vigorous growth of the cobra plant. The plants are rarely seen in standing water in nature. Because of this extreme intolerance to high temperature at the root, the cobra plant is not a very easy plant to maintain in cultivation. Even if you live within the perimeter of the cobra plant's natural distribution in Oregon and California, it is unlikely that you would have great success with growing cobra plants if you just leave them in a water-filled tray; you need to drop an ice cube or two on the pot everyday during the hot summer days!  

On the other hand, in the inland localities of northern California, cobra plants endure extremes of low temperature during the winter months, sometimes covered with frost, ice, and snow!

There is some debate as to which direction the cobra plant colonies face. From field observations, it is easy to see that Darlingtonia enjoys plenty of sunlight. Plants growing in a sunny location assume a colorful tint on the domed hood toward the orifice and the fishtail appendage -- a definite advantage in attracting prey -- that is absent in all-green, shade-grown plants. Many major colonies face south-east. Rondeau (1995) attributes this to local hydrology of the region more than any other factors.  There are many fine colonies in the mountain meadow whose slope is so slight that it is rather academic to speak of colony orientation (in relation to the amount of sunlight the plants receive). And there are some colonies facing north. We also find large colonies that are over-grown by shrubberies and conifers, with rather limited sunlight, regardless of their orientation. Darlingtonia seems to persist well in those low-light conditions as long as there is plenty of water supply, though the long-term health of such colonies is uncertain.

OK - Rebecca M. Austin

Throughout the recorded history of Darlingtonia, Rebecca Austin was the first to study the plants in detail and make pioneering field work. (Juniper, et al. 1989)  Moving to northern California with her husband and their three young children, Rebecca Austin was fascinated by this unique California pitcher plant. Living near great cobra plant sites, including Butterfly Valley (now a protected nature preserve), she spent many days observing the plants in the field, sometimes carrying her sewing to the colony, even putting out a tent for overnight observations. She also pursued her observation in the midst of a violent thunderstorm, convincing herself that the rainwater did not enter the pitcher. From 1875 to 1877, she diligently communicated her detailed field observations to W. M. Canby, a botanist in the East. Canby sent stationery to help her work and encouraged her observations. The then-newly-published book "Insectivorous Plants" by Charles Darwin was sent to her to aid her studies.  Rebecca Austin had already noted that the plants required plenty of cold water for healthy growth.

Trap Structure and Attraction 

The pitcher looks light yellow-green on the domed hood and gets darker green toward the base. The area around the pitcher opening leading to the fishtail appendage assumes a reddish coloration in plants growing in the sun.

The basic trap structure of the pitcher leaf is similar to that of the eastern pitcher plants. Together with the attractive colors of the leaf, prey is lured to the trap by nectar-secreting glands scattered over much of the pitcher exterior. To attract crawling insects on the ground, there are nectar trails around the pitcher tube leading to the pitcher opening.

The fishtail appendage provides a convenient landing site for flying insects. It is a perfect feeding ground as well for the nectar secretionsis abundant. Its surface is covered with short, stiff hairs, pointing toward the pitcher opening. This encourages the insect to ascend its way along the fishtail. The dome and the upper part of the pitcher are scattered with many areoles, called fenestrations. These patches are completely void of chlorophyll and other pigments, forming truly translucent windows. Seen against a blue sky, the brightly lit ceiling of the dome persuades the insect, already enjoying nectar on the fishtail appendage, to venture into the dome interior. 

The leaf edge of the orifice rolls inwards, forming the “nectar roll” around the pitcher opening. This is  where the nectar production is most abundant. Once inside, the fate of the insect is almost decided. The rolled-up inner margin of the pitcher opening somewhat conceals the true exit from insect's view, and the light windows provide the illusion of false exits. The hooded dome interior is covered with short, stiff hairs (1 mm) all aligned in the direction toward the spiral tube. The insect, instinctively seeking an exit in the direction of light, often slams against the dome ceiling in its attempt to fly through, and tumbles down into the spiral depth of the cobra leaf.

Right below the dome interior extends a hairless, detachable waxy zone which offers an extremely poor footing for the insect. Further down along the pitcher, as the tube gets narrower, there grow long, intermeshing, down-pointing hairs designed to prevent insect's ascent. This retention zone continues almost to the end of the pitcher. At the very bottom lies a short, smooth zone where there is no glands. At the end of the summer season, pitchers in the field retain numerous exoskeletal remains of insect bodies at the tube base.

A younger pitcher leaf tends to assume a more tilted angle, with the forked appendage often touching the ground. In this posture, the appendage serves as a ladder leading to the pitcher opening for crawling insects, such as ants.

OK - Digestion and Absorption

The cobra plant normally retains small amount of liquid at the bottom of the pitcher. The well-developed domed hood structure of the leaf all but precludes the possibility of rainwater entering the pitcher. In Darlingtonia, an unopened pitcher retains some liquid.

Unlike most species of the eastern pitcher plants, the cobra plant does not possess any digestive glands in the pitcher interior and no enzyme secretions has ever been detected. The digestion of prey is carried out solely with the aid of externally introduced bacteria.

"In Darlingtonia", Juniper et al. note, "which we consider to be a relatively primitive carnivore in some respect, there are nectar glands, but the glands of the digestive zone do not appear to secrete enzymes. Thus, nectar secretionsmay have developed before enzyme secretions in a species which relies on a larval-protozon-bacterial chain breakdown for digestion of prey. " Juniper et al. also note, "...nectar secretionsmay more readily develop than enzyme secretions because it was probably based initially on the exudation of phloem contents already present, needing only to become more concentrated. A mechanism was already present in floral nectaries."

In spite of the absence of enzyme production on the part of cobra plants, it is a mistake to consider the trap merely a passive pitfall. Studies have shown that a certain chemical stimulation (like beef broth) precipitates a large amount of fluid secretions into the pitcher. The cobra plants respond quickly to chemical stimulation as the result of prey falling into the pitcher and actively causes a copious increase of pitcher fluid, as reported by Austin and others, in order to aid the digestion by bacteria.

The bottom part of the pitcher, where the liquid is usually retained and where the digestion takes place, does not possess any special glands. The permeability of the inner wall due to cuticle discontinuity allows the absorption of digestive material into the leaf tissue.

In the pitcher fluid, many white worms are often found, apparently feeding on the captured prey. This observation was first made by Rebecca Austin. I have made similar observations. She described it as "recently captured insects rapidly covered with white 'worms' - hundreds of such 'worms' in some tubes" (Juniper, et al). Rebecca Austin also reported white larvae in unopened pitchers.

..... PHOTO of worms

OK- Inflorescence

In one of nature's most spectacular floral displays, colonies of cobra plants throughout California and Oregon are covered with eerie red flowers during the months of early spring. A flower bud forming in the rosette center during the cold winter months develops into a tall scape, often reaching a height of 70-80cm at the time of flowering. A red solitary flower blooms in April-May in a pendulous position at the tip of the tall scape.

The dainty flower has five petals, which hang from the base of the dangling flower. A pale-yellow petal is heavily lined with red veins, making the flower appear bright red.  The tip of each petal comes together to form a slightly elongated sphere. Each petal has a small notch on each side two thirds of the way down from the attached base. When the corolla sphere is formed, each adjacent notch pair creates one circular opening, five in all. Five elongated yellow sepals softly overhang the red corolla. Inside the corolla hangs a bell-shaped ovary surrounded by 15 or so stamens. At the ovary base grows a tiny, five-lobed stigma. 

Just before the opening of the flower, the sepals tightly fold the down-pointed spherical corolla.  PHOTO IF BUD

Upon opening, as the sepals loosen, the anthers shed an ample amount of pollen. (The anthers continue dehiscing pollen for 11-23 days, according to Elder 1994). A slight tap of the flower causes the massive amount of powderly pollen to fall out from the corolla opening where petal tips meet. The flower appears to be protandrous, that is, the stigma does not become receptive initially. This is a common strategy seen in flowering plants to avoid, or discourage, selfing.

In northern California, flowering starts in early May and lasts for a month. Red petals still remain on the flower for another few weeks. When I visited the site in early June, no pollen remained in the flower and my attempt to observe the corolla interior readily broke off the now somewhat dry petals. In the same habitat, a colony located in the shade appeared to be blooming late by a few weeks compared with the population in the open, sunny location. In southwestern Oregon, the bloom typically starts a few weeks earlier than in California habitats, in mid-to-late April, and continues through the month of May.

The age of the flowers are measured to be close to each other, a phenomenon often interpreted to be a strategy against unpredictable pollinators (Elder 1994). Also, Darlingtonia is one of early bloomers of the field in northern California habitats, possibly an attempt to avoid competition with other flowers (Elder 1994).

One observation I made is that the flower has a rather distinct smell, something of green vegetation freshly cut. It is a pleasant scent, of a fragrance of perfume, and fairly strong, too, for a freshly opened flower. The scent lasts for a week or two. 

Pollination

An insect pollinator enters the corolla through one of the five circular openings. When the flower opens in a pendulous position, the five-lobed stigma projecting under the bell-shaped ovary is located right at the same level as the circular openings. This causes the pollinator to brush the stigma immediately upon entry and deposit the pollen collected from the previously visited flower. Fifteen or so stamens hang around the ovary base inside the corolla. As the insect pollinator ascends in the corolla interior in search of nectar, it now collects pollen of that flower. When the insect is ready to leave the flower, it does so by sliding down the ovary slope and exiting the flower either through one of the circular openings or by pushing the petal tips. This way, it is unlikely the insect will touch the stigma again -- which is somewhat hidden under the expanded bottom of the bell-shaped ovary. This structure seems to encourage cross-pollination by reducing the chance of selfing.

Though significantly different in appearance from the pitcher plant flowers of the East, a petal of the cobra plant flower also has a tiny notch, as in Sarracenia flower, both serving as a pollinator entrance. It is intriguing to speculate that this may suggest some evolutionary commonality between these two pitcher plant genera belonging to the same family.

Elusive Pollinator

There is no field report supporting the above pollinator scenario. It is a common observation for those who have visited a colony in September that countless scapes stand in the cobra field, holding fruit capsules filled with thousands of viable seeds. Whoever is responsible for the abundant crop of seeds of the cobra plants, the unidentified pollinator somehow succeeded in eluding discovery for the past 150 years.

Rebecca Austin, through her keen observations, suspected the ever-ubiquitous spider to be a pollinator of cobra plants. Many observers after her witnessed spiders and their webs in the cobra plant flowers. Indeed, it is often difficult to find a flower totally free of spider web. This observation holds true for both Oregon and California habitats.

Schnell (2002) bets pollination biologists will one day identify a bee to be the yet-unknown pollinating agent for the cobra plants, as for Sarracenia flowers in the East. Rondeau (1995) points out the total lack of investigation on nocturnal creatures.  Some entomologist claims the unpleasant odor of the flower clearly suggests pollination by flies (Rondeau 1995).****

In April 6 though June 16, 1996, a research attempting to identify the pollinator of the cobra plants was conducted in Oregon (Nyoka 1999). Only a few sightings of insects actually entering the flower have been recorded during the daytime observations. Using sticky trap cards and aerial netting in a large cobra plant colony in southwestern Oregon, nearly 1800 flying insects have been captured and analyzed. Of 27 species found to carry pollen, only 8 individual insects representing 4 species carried Darlingtonia pollen. Ten of 14 arachnid species, totaling some 80 individual spiders, collected in and adjacent to the flowers were found to carry Darlingtonia pollen. The report concluded that the evidence of pollination by several insect species was obtained, though noting the insect pollination may be infrequent. The report also suggests that the spiders may be playing a roll of pollinators for the plants.

Could the spiders be a real (legitimate) agent of pollination for which the flower has evolved over millennia? When it comes to cobra plant flowers, delicate petals are twisted by the web, sepals and bracts tied together, the stamens inside often bundled together by the spider web. I have seen some flowers where the stigma is completely shielded by the web. Many observers may feel that this is not a matter of a flower-pollinator arrangement. Rather, this is more like a case of massive spider infestation! Virtually all flowers in the field are occupied by spiders. It is way too risky to enter the flower. Yet-to-be-identified pollinators are prevented from rendering the service because of the uninvited arachnid visitors.

Is the fertilization of the flower already completed by the time the spider commandeers the flower? In 2004, I attempted to answer this question. In early May in northern California, flowering season had just started, as evidenced by some flower buds among open flowers. I arrived at a cobra plant colony very early in a morning. The flowers were still covered with morning dews. The air was chilly. As I looked around, almost all flowers were tendered by spiders, sometimes three, four small spiders per flower. A fierce web construction had already been well underway. On one flower bud, I noticed a spider hiding under a bract near the crooked scape, waiting for the flower to open. In a matter of a week or so, no flowers would be free of webs. As the sun rose, the spider activities subsided. Perhaps they were hiding in the flower. Flies, bees, butterflies, and dragonflies were seen, but none landed on the flower. As the darkness enveloped the cobra plant blossom, moths started to fly over the grassland. Many crane flies were also observed near the water. I sat alone, being gazed at by hundreds of silent, eerie red faces, in the darkness of the forest. Every year, a couple of deer falls victim of the mountain lion, a forest ranger had told me. No promising nocturnal pollinators were observed on this day....

Conclusion

In the absence of other creatures transporting pollen, at least not in sufficient frequency, do we have to conclude that the spiders are indeed the major pollinators of the cobra plants? I am hard pressed to accept this conclusion. If the spiders are freely walking around inside the corolla, how is it possible to avoid self-pollination? The unique floral structure, coloration, fragrance... all these have evolved to attract spiders for their pollinating service?

Could it be that the original insect pollinators have been chased away by the massive invasion of spiders in the course of evolution? And, as it turned out, the plants are benefiting from this arrangement, as seen in the healthy crop of the seeds?    

 Glistening silver silk, blowing in the gentle spring breeze, in the blossoming cobra plant colony tells us the complexity of the ecosystem.

Germination & Growth

In nature, the seeds set by September. A tall scape (that stands 80cm at the time of flowering) grows further after fertilization as it straightens itself from pendulous to erect posture, often reaching 100cm or more in height. Each mature fruit capsule contains a large quantity of seeds (1160 seeds on average, on unmanipulated flowers, and more than 2000 if extra pollen added manually, according to Elder, 1994). A characteristic seed has numerous tiny projections for animal dispersal. Floating seeds in the stream may find new colonies down the stream.

Seed Stratification

The Darlingtonia seeds require stratification. That is, the seeds have to be exposed to low temperature before germination. In nature, the seeds do not germinate until spring to prevent the loss of new seedlings during the winter months. One may find tiny seedlings in the field with juvenile leaves which are tubular with a narrow pointed tip. In cultivation, the seeds can be forced to germinate in the same year by storing them in the refrigerator in a damp medium for a few weeks prior to sowing.

The cobra plant, for its size, is a rather slow grower.  After germination, it takes two to three years for juvenile, hollow, pointed-end leaves to assume the characteristics of a mature pitcher.  A few more years are required for the plant to flower. The plant continues to grow, producing larger leaves every ensuing year until it reaches its size maturity in 7-10 years from the seedling. 

The cobra plant also shows vigorous vegetative reproduction. The mature plant sometimes produces another growth point in the rosette center, eventually growing into two plants. In addition, the plant habitually produces long underground runners, or stolons. The tip of the stolon develops into a new plant. This ability of the plant to reproduce asexually often results in rather dense growth characteristics as typically seen in the wild cobra plant populations throughout their distribution.

OK - Pollinator/Prey Dilemma

A strange sense of similarity between flower and trap of this species was felt by workers observing the plants in the field. If this dual attractiveness also extends to the insect world, a pollinator/prey paradox may arise. Are the flower and the pitcher designed to attract the same insects? If so, aren't they competing for the same visitors to the plants, leading to a potential pollinator/prey dilemma? Given the average height of a mature pitcher leaf in the range of 40-60cm in nature, a tall scape typically grows to 70-80cm in height. This seems to offer some "spatial" separation between pollination and prey-trapping zones. Although varied depending on the locality and perhaps also on the severity of the previous winter, field observations show a relatively small number of functional traps remain at the time of anthesis. This does offer a "temporary" separation of a month or so for fertilization, before new pitchers become fully grown and functional. I have seen some large colonies in Oregon where pitchers of the previous season were well preserved into flowering, though key attractants such as nectar and brilliant coloration were not present.

Anthocyanin-Free Population "Othello"

A population of anthocyanin-free plants has been found in California (Elder 1994, Meyers-Rice 1997). The flower has no red venation and is totally yellow. The pitcher is also all-green to yellow, without any red pigmentation. The plants are identical to the normal variety in all other aspects. Meyers-Rice (1998) gave the plants a cultivar, Darlingtonia californica "Othello". (The cultivar is a "cultivated variety" that is registered with an International Registration Authority, such as International Carnivorous Plants Society.)   

Compass Plant

May blossoms are soon to be followed by a rush of fresh, green, tubular leaves shooting up from the rosette center, signaling the onset of a trapping season in the cobra plant country. These are the first leaves of the season and are the tallest of all the leaves to follow.  PHOTO

It is Rebecca Austin who first reported the compass nature of the cobra plant. She observed that the plant always produced pitcher leaves in pairs, a total  of 10-18 new leaves each year. The first two large leaves in the spring would face the north-south direction, with the first leaf always being the tallest of the year. The next two would emerge in the east-west direction, thus, the first four pitchers of the season pointing in the direction of the four major axes of the compass. Some others confirmed her observations. These four leaves stand far above all the subsequent leaves.

Schnell (2002) noted his cultivated plants obeyed this compass rule. He then turned the pot 90 degrees. The plants produced the leaves according to the old orientation in the first year but adjusted to the new orientation the following year.

My field observation confirmed this compass tendency, though occasional violators have been noted. It should be mentioned that it is not always easy to distinguish individual plants in the field especially when plants are forming a dense colony. Also, since a Darlingtonia rhizome itself tends to grow horizontally in one direction, which way the emerging leaves are pointing to is sometimes not so clear. Incidentally, the emerging direction of the leaf (presumably governed by the compass rule) and the characteristic "spin" of the pitcher are two separate things. Thus, the final orientation of the cobra head (or the direction the fishtail appendage points to) is the sum of the initial leaf direction and the leaf twist (which can be 90-270 degrees, Rondeau 1995). 

In Darlingtonia,  as noted by Rebecca Austin, all the leaves are not the same height. Indeed, the leaf size within a given mature plant varies dramatically, from full 40-60 cm at the tallest end all the way down to less than a few inches. Unlike the pitcher plants in the east which produce more or less the same sized adult leaves from the rhizome, the cobra plant produces progressively small er pitcher leaves during its yearly growth cycle. The cobra plant produces the tall leaves early in the season, and the subsequent leaves tend to be shorter than the previous. The very first leaf to emerge right after the flower is the tallest of the new season and the next one the second tallest. (Based on the compass nature, this first pair of leaves presumably point to the north-south orientation.)

A field observation I made in northern California in one spring, choosing a mature, flower-bearing specimen, that was retaining the previous year's pitchers fairly well, yielded the following. ==========

Total 19 leaves (prev years) - 45,37,33,33,28,20,18,17,17,14,14,13,12,11,10,10,9,5,5.

New leaves 25 & 9 and the second bud 20 & 2.

Scape 60 cm

3 stolons - 40-50cm long each -- each having 4,5 leaves of 3-7 cm high.

OK - Health of Habitat

Some of the large cobra plant habitats are more than 150 years old. "One might expect that the improvement of the soil, resulting from the sustained capture of insects, would result in the competitive invasion of more vigorous species.” Juniper et al. notes, referring to the constant streams flowing on the soil surface, "That this is not the case with Darlingtonia may be due in part to the dynamic nature of its habitat, forever removing the nutrient-rich humus that it produces. In this respect, Darlingtonia differs from its relative Sarracenia and many other carnivores which continually destroy their own habitat."

The rejuvenation benefit of carnivorous plant habitats in general due to periodic, naturally occurring fires is recognized by various authors. Just as in the eastern pitcher plant habitats, Darlingtonia also benefits from the natural fires in their habitats. The low intensity ground fire is said to pose little damage to the established cobra plant colonies.

 ----
* See Rondeau 1995, for the history of how this unique plant from the West was "named for a man who never saw it, never collected it, and never even visited the golden state!".

**  Some feel the three genera (Sarracenia, Darlingtonia and Heliamphora) of New World pitcher plants currently comprising the entire family Sarraceniaceae are distinct enough, in terms of both floral and vegetative structures, that the creation of the separate families are warranted.  (Also see Phylogeny)

*** I have noted that a plant from an underground stolon can have the opposite twist. One large cobra plant I observed had several runners, from the tip of which had emerged a new young plant. Still connected to the parent plant by stolons, two of them exhibited counter-clockwise twist while the rest of the pack, including the parent, all have clock-wise leaf twist.