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Issue No. 158 - April 3, 2005
by Sue Sweeney
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There should be a national skunk cabbage day. Skunk
cabbage is a wonderful native plant, first to bloom
after the witch hazel, the silver maple, and the
crocus, as much a symbol of woodland spring as the
returning robins. This ancient, lovely and
mysterious guardian of the wetlands is a plant about
which many lies are told.
Common wisdom is that skunk cabbage is a stinky,
ugly trash plant. Wrong. I have read that the smell
comes only from the leaves that only unfold after
the flowers are done but that the smell's purpose is
to attract pollinating insects. Not possible. It is
said that you can eat raw skunk cabbage leaves after
boiling; other reports indicate that you'd do better
to invite an actual skunk into the kitchen because,
then, at least the skunk would (possibly) enjoy the
process. |
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picture: skunk cabbage heralding
spring at the Bartlett Arboretum, Stamford CT, March
2005 |
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FAMILY: Our native eastern skunk cabbage,
Symplocarpus foetidus, is in the Arum family (Araceae),
like the native jack-in-the-pulpit, and the tropical calla
lily. The first interesting think about skunk cabbage is
that even though it is as common as the mud in which it
grows from Southern Canada to Northern Georgia, there's only
one species of it. It is so suited to its environment that
part of the clan has not evolved into a genetically separate
species. (The yellow-spathe western skunk cabbage,
Lysichitum americanum, is also in the Arum family but
different genus, so it is a cousin, not a sibling, and has
different qualities.) Tropical Arum cousins that you might
be harboring at home include philodendron, dieffenbachia (dumbcane),
and aglaonema (Chinese evergreen).
IMMORTAL?: Eastern skunk cabbage has such an
amazing survival strategy that botanists theorize
that the plant's central rhizome could live for at
least thousand of years, if not indefinitely.
Specimens several hundred years old have been found.
It is believed that the "limiting factor" for the
life of a skunk cabbage is that it requires a
year-round muddy bed, and, after hundreds of years,
swampy places tend to dry up as the accumulation of
decomposing plant litter raises the ground level.
(Too bad the same can't be said from most Arum
houseplants – they're tough but not nearly
immortal).SEEDS: Eastern skunk cabbage
doesn't appear to be able to spread from the roots;
so to make new plant colonies, it needs to make
seeds. So, we'll start there. The hard, pea-size
seeds ripen in late summer, and drop into the mud.
Some are carried away by animals or floods, the rest
either die or germinate in place. |
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pictures:
Young skunk cabbage seedling
putting down roots in the foreground; older
plant with erosion-exposed roots in the water.
Second picture (below): The
rarely seem stem of a skunk cabbage spathe –
generally this have been pulled underground by
the contractile roots. Both pictures: the
Bartlett Arboretum, Stamford CT, March 2005 |
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CONTRACTILE ROOTS: Most plants are
doomed to live (or die) exactly where and
how the seed falls but the eastern skunk
cabbage is blessed with a mobility device
called "contractile roots". The roots grow
downward, then contract, pulling the plant's
crown (a thick underground stem called a
"rhizome") deeper into the mud. Each year,
the plant digs itself deeper into the earth
and extends its anchor-roots farther down.
The young plants only have a few leaves: the
very old ones, many. You generally can't see
the plant's leaf or flower stems because
they've been pulled underground. The roots
of a mature plant are said to be so massive
that trying to dig them out is a complete
waste of time. |
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picture: particularly beautiful skunk cabbage
spathe, the Bartlett Arboretum, Stamford CT,
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ENVIRONMENT: Eastern skunk cabbage
want muddy roots all year round; they'll die
in places that get too dry in summer.
Conversely, while they love romping in the
spring floods with water up to their noses,
they don't like having their crown under
water all year. Thus, they are an
edge-of-wetlands plant – and a clear sign to
the hiker to stay back or risk damaging the
fragile wetlands community, as well as
bruising the skunk cabbage's leaves and
getting a nose full of a reek alternatively
described as like a raw onion only more so,
a skunk or rotting meat. While the smell
warns animals that the leaves are too high
in unpleasant compounds to be edible, it
also warns the human invader to back off the
wetlands. FLOWER: Eastern skunk
cabbage, like most Arums, has a hood
surrounding the flower stalk made from a
modified leaf. The hood is called a "spathe".
Inside the hood is a flower stalk, called a
"spadix", which is covered with tiny, light-colored
flowers with no petals. Since the hood never
opens much, you have to peek inside to see
the flowers. The flowers are said to be in
"bloom" when the stamens have grown above
the tiny flowers and are covered with yellow
pollen. |
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| picture: Close up of the blooming female
flower, the Bartlett Arboretum, Stamford CT, March 2005 |
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Actually, the botanists say that the female
flower parts ("pistils" or pollen receivers)
bloom first before the male parts ("stamen"
or pollen makers). In addition, the flowers
bloom from the top of the stalk down. Thus,
when the first female flowers are blooms,
they can't be pollinated from the same plant
since none of the male pollen-bearers are
blooming yet. What the plant ideally will
get is cross-pollination from an
earlier-blooming (and stronger?) plant. As
we seen time and again, many plants insist
on cross pollination to keep the species
strong. The eastern skunk cabbage, though,
is very smart. What if there's no other
plant or no other earlier blooming plant
around? It appears that if all else fails,
the eastern skunk cabbage should be able to
self-pollinate later in the season. (I
haven't seen this confirmed with a
biological study but there very well may be
one).
SPRING RITUAL: To get a head start
in spring, before the trees leaf out and
shade the ground, the eastern skunk
cabbage's flower-to-be forms in the summer
in the middle of the plant's crown. Look
down between the leaves, the round nub of
the spathe is there, curled and waiting.
Also made-ahead are the leaf cones. By early
winter, you'll often see next year's
cone-shaped furl of leaves poked up next to
next year's spathe, ready and set, just
waiting for the "go" signal.
Once the days lengthen enough to say
spring might come someday, the skunk cabbage
starts moving, literally. First, the spathe
rises so fast that the heat thrown off by
its growth can melt surrounding ice and
snow. Technically, the process is called
"respiration". (The heat is produced by
burning oxidizing carbs stored since last
summer in the rhizome – same as when you
exercise, assuming that you do, only you
don't have a rhizome to keep your fat out of
sight.) The eastern skunk cabbage's ability
to create heat, and then hold the heat in
inside the spathe is legendary among
botanists.
Apparently, the plant actual can keep the
tiny "room" inside the spathe at about 70F
for a period of about 2 weeks while the
plant is in active growth. Somehow the plant
senses temperature drop and speeds up
respiration. The theory is that the heat,
plus a faint carrion odor, attracts
pollinators, particularly flies. It
certainly does result in the early-waking
insects such as small flies, honey bees,
gnats and spiders having a warm place to go
at night. Some say that the attracted
insects drown in water accumulated in the
base of the spathe and then provide
nutrients for the plant. There are many
native bog carrion-consuming plants but the
weight of authority seems to be that the
skunk cabbage is not first and foremost an
insect-trapper.
The above-ground parts of the skunk
cabbage, being a very fast grower, are made
mostly of water and air, with very little of
the fibrous cellulose that stiffens woodier
plants. The resulting air pockets in the
spathe's walls make it a good insulator to
hold the heat, and the wall's dark color
helps absorb solar radiation. In addition,
the shape of the spathe creates a vortex so
that cold air flows in the wide opening
toward the bottom of the spathe, warms and
rises out the narrow top opening. This draws
insects in at the bottom and releases
insect-attracting odour out the top. |
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picture: Skunk cabbage's leaf
cone above the spathe, the Bartlett
Arboretum, Stamford CT, March 2005 |
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LEAVES: It is often said that the
leaves do not unfurl until flowering has
finished. However, it is probably more
accurate to say that the leaves start
unfurling once the outside temperature is
consistently warm enough to protect the new
leaves from frost damage. The furled leaf
cone, made with last summer's sun and water,
contains all of the plant's leaves for the
season. The plant, basically, just needs to
unfold the package and inflate the leaf
cells with air and water. Accordingly, the
leaves quickly reach massive proportions –
up to 3 feet long. Again, to grow this fast,
the plant uses mostly water and air. Hence
the need to grow in a swampy area where
there's plenty of fresh water in during the
early growing season.
This year, take the time to check out the
iris-like spiraling pattern of the opening
leaves. The leaves are an attractive green
anyway and the physical arrangement makes
then even nicer. But look fast. Skunk
cabbage leaves lack the thick, waxy skin
("cuticle") that most plants use to keep in
moisture. Consequently, skunk cabbage are
constantly sucking water from the ground, up
the stems, and through the leaves, then
transpiring the water into the air. Most
plants only transpire (sweat) when there's
too much relative water pressure in the
leaves due to the surrounding air being too
dry or the plant having sucked up too much
water. But the skunk cabbage has no choice
but to keep pumping water up and out. While
you're checking the leaves, see if you can
sense a difference in the humidity near
these plants.
But easy come is easy go. By early
summer, the trees have leafed out and are
shading the skunk cabbage's leaves so much
that the skunk cabbage's leaves are no
longer "profit centers" for the plant. The
leaves no longer get enough sun to produce
more food than they use, so the plant cuts
them loose. It walls off the capillaries
that once gave the leaves food and nutrients
from the ground in return for food
manufactured by the leaves using
chlorophyll, air and sun. As soon as the
water source is lost, because the leaves can
not stop transpiring, the leaves deflate
just as rapidly as they inflated in the
spring. Small holes appear; the leaves
droop. The next thing you know, there's just
a slimy, black smudge left on the ground,
like the Wicked Witch of the East. |
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pictures: skunk cabbage
spathe with leaf cones; all pictures: the
Bartlett Arboretum, Stamford CT, March 2005 |
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FRUIT: The eastern skunk cabbage
spends mid-summer, in the cool moist shade
of the tree canopy, sucking whatever
energy's left out of the deteriorating
leaves and making the leaves and spathes for
next year. It's also ripening the fruit made
by the pollinated flowers on the spadix. By
late summer, this year's spathe is long
gone. The fruit clustered along the spadix,
now open to the air but still just above
ground level, have turned the dark red to
black. The fruit will either fall as the
spadix itself disintegrates or will by eaten
by birds and furry critters.
USE: Skunk cabbage obviously pulls
its weight in the eco-chain by providing
early-spring board and room for the
pollinators, anchoring the soil against
erosion, keeping hikers out of the wetlands,
and enthralling botanists. In addition, a
few animals are not as bothered by the
calcium oxalate crystals in the leaves, and
other plant parts as we are. While few
humans die from ingesting Arum plant
substances, few choose to repeat the
experience of a "strong inflammatory
reaction in the mouth and esophagus" (means:
it burns a whole lot!). Black bears, wild
turkey, and Canada geese are reported to be
among the animals brave enough to eat the
young leaves, buds or roots. (As far as I
can tell, deer and rabbit won't touch it.)
The seeds are said to be eaten by squirrels
(of course), other wood rodents, ring necked
pheasants, ruffed grouse and bobwhite. |
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| picture: skunk cabbage spathe and several
leaf cones peak from behind a decaying birch log, the
Bartlett Arboretum, Stamford CT, March 2005 |
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Native Americans did use the leaves and
roots for food and medicine. Apparently, the
trick is to dry the stuff for at least
6-months before use. There are a bunch of
other in's and out's to human consumption,
so don't try it without reading up
thoroughly first. Lastly, I've read that the
smell from the raw crushed summer leaves
will ward off insects, useful, though, only
if you're not warded-off first. |
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| picture: skunk cabbage spathe , the
Bartlett Arboretum, Stamford CT, March 2005 |
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