April 6, 2017
The plant was discovered in 1841 by William D. Brackenridge, assistant botanist of
the U.S. Exploring Expedition, in a marsh a few miles south of Mt. Shasta in
northern California. John Torrey, a distinguished botanist of the 19th
century, recognized a close relationship to the eastern pitcher plants yet a
clear difference in floral characteristics, and established a new genus in the
pitcher plant family, naming it Darlingtonia californica, in honor of his friend and
botanist, William Darlington.* The genus Darlingtonia is
monotypic, i.e. only one species in the genus.
The pitcher plant family Sarraceniaceae contains two
other genera, Sarracenia (Eastern North American pitcher plants) and Heliamphora
(the marsh pitcher plants, from South America).**
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-like appendage projecting
downward from the front edge of the opening. A peculiar feature of the plant is
that the leaves twist about 180 degrees as they grow. As a
result, the pitcher openings tend to face outwardly from the plant center. This
conceivably provides wider coverage for prey acquisition. The
direction of the twist seems to be just about even between clockwise and
counter-clockwise in nature, though within a given individual the direction
In a typical natural habitat, a mature pitcher leaf
stands between 40-60cm tall. Leaves reaching 100cm
(etiolated) are found in some
low-light conditions. Seen in the field, the overhanging hood of the pitcher
leaf gives an impression of a deadly cobra about to strike in imminent defense,
hence the common name. Other names for the plant include "cobra lily" and
the California pitcher plant.
The distribution of cobra plants is limited to
northern California and the adjacent southwestern part of Oregon, where the colonies
are highly localized in characteristic marshy habitats often with fresh, running
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 present 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 setting that
the colonies of the cobra plants thrive. The plants' fondness for this particular
setup is clearly manifested in the astonishing similarity of many a montane
habitat throughout their range.
Many sites are also known to be located
on or near magnesium-rich (but nutrient-poor) serpentine outcrops — with
ultramafic rock formations containing elevated amounts of chromium and nickel
(which may be toxic to plants). The soils in these habitats are acid and poor in
nutrition, in general conformity with other carnivorous plant habitats. These
nutritionally poor and phytotoxic soils provide a competitive advantage for
cobra plants possessing a carnivorous lifestyle.
Many populations are found in the montane habitats at an altitude of up to 2400m, although some vigorous stands of cobra
plants can be seen almost at the sea level along the
Oregon coast (south of the city of Florence). The plants seem to be tolerant to this climatic
variation (Juniper, et al. 1989).
As for accompanying carnivorous plants, cobra plants are
often found in the company of Drosera rotundifolia (round-leaf sundew) at the southern end of its range
(Rondeau 1995). In southern Oregon, there are some colonies where Pinguicula
macroceras ssp. nortensis (butterwort) grows extensively alongside Darlingtonia.
Rondeau (1995) 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.
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).
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
happen to live
within the perimeter of the cobra plant's natural distribution in Oregon and
California, it is unlikely that you would have great success
in 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!
other hand, in the inland localities of northern California and adjacent Oregon,
cobra plants endure extremes of low temperatures 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 locality assume a colorful tint on the domed hood toward
and the fishtail appendage -- a definite advantage in attracting prey, that is absent in
all-green, shade-grown plants, in nature or in cultivation. 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 view of the amount of sunlight the plants receive). And there are some colonies
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.
Rebecca M. Austin
Throughout the recorded history of Darlingtonia, Rebecca
Austin was the first to have studied the plants in detail and made 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 Californian 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.
She continued her observations for several years, from 1873 to 1879.
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 assist in her studies.
Trap Structure and Attraction
The domed pitcher looks light yellow-green on the hood and
gets darker green toward the base. The area along the pitcher opening through
the fishtail appendage assumes a reddish coloration in plants growing in the
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
The forked, fishtail appendage has numerous nectar glands.
Its surface is covered with short, stiff hairs, all pointing toward the
pitcher opening. For a flying insect, the fishtail appendage provides a
convenient landing site, as well as a feeding ground. Further toward
the domed hood, the insect finds more nectar around the pitcher opening. 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.
The hooded dome interior is covered with fine hairs.
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 the blue sky, the brightly-lit ceiling of the dome
encourages the insect,
already enjoying nectar on the fishtail appendage, to venture into the dome
Once inside the dome, 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 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
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, downward-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
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).
In the field, at the end of the summer season, pitchers are
often seen half-filled with exoskeletal remains of insect bodies, attesting to the
trapping efficacy of the pitcher leaves.
Digestion and Absorption
The cobra plant normally retains small amount of liquid
at the bottom of the pitcher. Unlike the eastern pitcher plants, 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. Studies have shown that a certain
chemical stimulation (like beef broth) precipitates a large amount of fluid secretions into the pitcher. The insect prey falling in the pitcher equally causes the
fluid level to rise. This reaction to the chemical stimulation is also seen in
some eastern pitcher plants.
Unlike most species of the eastern pitcher plants, however,
the cobra plant does not possess any digestive glands in the pitcher interior
and no enzyme secretions has 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 secretions may have developed before enzyme
secretions in a species which relies on a larval-protozon-bacterial chain
breakdown for digestion of prey. Presumably this dependency could have been the
integral feature in the development of present-day highly adapted species."
Juniper et al. also note, "...nectar secretions
may 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."
The bottom part of the pitcher, where the liquid is
usually retained and the digestion takes place, does not possess any
special glands. The permeability of the inner wall due to cuticular discontinuity
allows the absorption of digestion
products 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. She described it as ...
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 May through June. A flower bud forming in the rosette center
the cold winter months develops into a tall scape by spring, often reaching a height of 70-80cm. A red,
solitary flower blooms in May in a pendulous position at the tip of the tall scape.
Though significantly distinct in structure from the
pitcher plant flowers of the East, the cobra plant flower seems to exhibit some
evolutionary commonality with those of the eastern pitcher plants. (See below for a
tiny notch on the petal serving as a pollinator entrance, as in Sarracenia)
The dainty flower has five petals, which hang from the base
of the dangling flower. 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.
pale-yellow petal is heavily lined with red veins, making the flower appear
bright red. Five elongated yellow sepals softly overhang the red corolla. Inside the corolla a
bell-shaped ovary hangs at the base,
surrounded by 15 or so stamens.
An insect pollinator enters the corolla through one of the
five circular openings. Since the five-lobed stigma projecting under the
bell-shaped ovary is located right at the same level as the circular openings,
the pollinator is bound to brush the stigma immediately upon entry and deposit the pollen collected from the previously visited flowers.
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. 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 and reduce the chance of self-pollination.
There is only a few field observations
of pollinator visitation. It is a common observation for those
who have visited a colony in September that countless scapes stand in the cobra field,
supporting capsules filled with hundreds of viable
seeds. Whoever is responsible for the abundant crop of
seeds, the unidentified pollinator has eluded discovery for the past 170 years.
Rebecca Austin, through her keen observations, suspected the
ever-ubiquitous spider to be a pollinator of cobra plants. In the
field, it is quite common to see spiders and their webs on the cobra plant flowers. Indeed, it is often difficult to find a flower totally free of
spider web. Glistening silver silk, blowing in the gentle spring breeze, in the
blossoming cobra plant colony tells us the complexity of the ecosystem.
Schnell (2002) bets pollination biologists will one day
identify a bee to be the yet-unknown pollinating agent for the cobra plants, as
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).
My personal observation is that the cobra plant flowers have a very pleasant,
rather strong, sweet fragrance, especially when the flowers are freshly opened..
Germination & Growth
The May blossom is 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
the tallest of all the leaves for the year.
In nature, the seeds set by September. A tall scape
(that reaches a height of 80cm at the time of flowering)
further after fertilization as it straightens itself from pendulous to erect
posture, often reaching 100cm or more in height. Each flower capsule is filled
with hundreds of viable seeds. A characteristic seed has numerous tiny,
air-filled projections for wind dispersal. Floating seeds in the stream may find new colonies
down the stream. The seeds germinate the next spring. One
may find tiny seedlings in the field with juvenile leaves which are tubular with a narrow pointed tip.
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 stolons, or underground runners. The tip of these
stolons develops into a new plant. This
ability of the plant to reproduce asexually often results in rather dense growth characteristics as typically
in the wild cobra plant populations throughout their distribution.
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" isolation of a month or so for fertilization, before new pitchers become
fully grown and functional -- though I have seen some large colonies in Oregon
where pitchers of the previous season were well preserved into flowering.
of anthocyanin-free plants has been found in California by C.
L. Elder (1994). The flower has no red venation and is totally yellow.
The pitcher also lacks any red pigmentation and remains all-green to
yellow. The plants are identical to the normal form in any other respect.
Meyers-Rice (1998) gave the plants a cultivar, Darlingtonia californica
"Othello". (Cultivar is a "cultivated variety" that is
registered with an International Registration Authority, such as
the International Carnivorous
This variant has since been formally described as
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,
and these four large leaves standing far above all the subsequent ones. Some
others confirmed her observations.
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. Incidentally, the emerging direction of the leaf
(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 (90-270 degrees, according to Rondeau 1995).
Health of Habitat
Some of the large cobra plant habitats
are more than 100 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
danger 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.
*** I have noted that a plant from an
underground stolon can have the opposite orientation. My large cobra plant has
produced several runners, from the tip of which has emerged a new young plant.
Still connected to the parent plant by stolons, two of them exhibit
counter-clockwise twist while the rest of the pack, including the parent, all
have clock-wise leaf orientation.