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TOPIC: mistletoe
http://groups.google.com/group/entstrees/browse_thread/thread/917b854fb43824c0?hl=en
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== 1 of 3 ==
Date: Sat, Dec 22 2007 4:56 pm
From: ForestRuss


ENTS:

This came to me via another list and I thought some of you might like
learning a little more about mistletoe.

Russ

Mistletoe has it all!

Mistletoe is a parasitic plant of the genus Phoradendron, with at least 24
species native to the United States, Puerto Rico and the Virgin Islands. It's
considered medicinal by some and invasive by others. Myths and folk uses of
mistletoe abound as part of many ancient and modern traditions around the
world. Here is an article by the USGS that highlights many of the interesting
facets of mistletoe. I've also included several links at the end to other
articles that venerate or denigrate this famous (or infamous) medicinal plant:

USGS 2007: Not Just for Kissing: Mistletoe and Birds, Bees, and Other Beasts
http://www.usgs.gov/newsroom/special/mistletoe/

Perhaps some of you have already experienced a sweet holiday smooch or two
under the Christmas mistletoe, enjoying this fairly old kissing ritual for
people. But mistletoe is important in other vital ways: it provides essential
food, cover, and nesting sites for an amazing number of critters in the United
States and elsewhere. In fact, says Rob Bennetts, a USGS research scientist,
some animals couldn't even survive without mistletoe, including some birds,
butterflies, and insects. But first, a little bit about the plant. The
white-berried Christmas mistletoe we hang so hopefully in places where our
sweethearts will find us lingering, is just one of more than 1,300 species of
mistletoe worldwide. Globally, more than 20 mistletoe species are endangered. Two
kinds of mistletoes are native to the United States: the American mistletoe (the
one commonly associated with our kissing customs) and the dwarf mistletoe.
American mistletoe is found from New Jersey to Florida and west through Texas.
The dwarf mistletoe, much smaller than its kissing cousin, is found from
central Canada and southeastern Alaska to Honduras and Hispaniola, but most
species are found in western United States and Mexico. Mistletoe is no newcomer
to this country: excavations of packrat middens reveal that dwarf mistletoes
have been part of our forests for more than 20,000 years. Some fossil pollen
grains even indicate that the plant has been here for millions of years. Says
Bennetts: "Mistletoes should be viewed as a natural component of healthy
forest ecosystems, of which they have been a part for thousands, if not millions
of years."

Thief of the Tree
The thing that all mistletoes have in common is this: all grow as parasites
on the branches of trees and shrubs. In fact, the American mistletoe's
scientific name, Phoradendron, means "thief of the tree" in Greek. The plant is
aptly named: it begins its life as a handily sticky seed that often hitchhikes
to a new host tree on a bird beak or feather or on mammal fur. In addition to
hitchhiking, the dwarf mistletoe also has another dandy way of traveling to a
new host tree: the seeds of this mistletoe will, like tiny holiday poppers,
explode from ripe berries, shooting a distance as far as 50 feet. One
researcher said that if you put ripe berries in a paper bag and shake it, it sounds
just like popping popcorn. For the most part, the mistletoe is pretty darn
cavalier about what host tree it finds -- dwarf mistletoes like most kinds of
conifers; American mistletoes are found on an incredible variety of trees. Once
on a host tree, the mistletoe sends out roots that penetrate the tree and
eventually starts pirating some of the host tree's nutrients and minerals. In
actuality, though, mistletoes are not true parasites; instead they are what
scientists call "hemi-parasites" because most of them have the green leaves
necessary for photosynthesis. Still, it seems like a pretty lazy life for most
mistletoes: a little photosynthesis here and there and a lot of food and water
stolen from their unsuspecting benefactor trees. Eventually, mistletoes grow
into thick masses of branching, misshapen stems, giving rise to a popular
name of witches' brooms, or the apt Navajo name of "basket on high."

Birds and the Mistletoe Trees
The plant's common name -- mistletoe -- is derived from early observations
that mistletoe would often appear in places where birds had left their
droppings. "Mistel" in the Anglo-Saxon word for "dung," and "tan" is the word for
"Twig." Thus, mistletoe means "dung-on-a-twig." Yet even though bird droppings
cannot spontaneously generate mistletoe plants, birds are an important part of
mistletoe life history -- and vice versa. A surprising variety of birds use
or rely on mistletoe. In Bennetts' and other studies, a high abundance of
dwarf mistletoe in a forest means that more kinds and numbers of birds inhabit
that forest. Also, since the lifespan of mistletoe-laden trees is considerably
shorter than trees where the plant is absent, a higher number of tree snags
occupy mistletoe-laden woods. Not surprisingly, this means that more -- one
study documented at least three times as many -- cavity-nesting birds live in
forests with abundant mistletoes. The phainopeplas, a silky flycatcher, are
beautiful birds that live in the desert areas of the Southwest and West and are
especially dependent on mistletoe. Diane Larson, a USGS researcher, studied
mistletoes and birds in Arizona. "I found that phainopeplas, which rely on
mistletoe almost exclusively for food during the winter, were also the species
most likely to disperse the mistletoe seeds to sites suitable for germination
and establishment. Both the bird and the plant benefited from this
relationship," says Larson. This year, USGS is beginning a study on phainopeplas and
mistletoes that live on acacia and mesquite trees in the desert. Todd Esque, a
USGS researcher, said that his goal is to understand the distribution of the
host trees in relation to mistletoe patterns and bird behavior. "We know the
relationship is mutually beneficial for both species," said Esque. Some
research indicates that if mistletoe-berry production is poor, these birds may not
breed the following spring. But the phainopepla is just one of many birds
that eat mistletoe berries; others include grouse, mourning doves, bluebirds,
evening grosbeaks, robins, and pigeons. Naturalist and writer John Muir noted
American robins eating mistletoe in the mountains of California in the late
1890's. Wrote Muir: "I found most of the robins cowering on the lee side of
the larger branches of the trees, where the snow could not fall on them, while
two or three of the more venturesome were making desperate efforts to get at
the mistletoe berries by clinging to the underside of the snow-covered
masses, back downward, something like woodpeckers." Birds also find mistletoe a
great place for nesting, especially the dense witches' brooms. In fact, northern
and Mexican spotted owls and other raptors show a marked preference for
witches' brooms as nesting sites. In one study, 43 percent of spotted owl nests
were associated with witches' brooms. Similarly, a USGS researcher found that
64 percent of all Cooper's hawk nests in northeastern Oregon were in
mistletoe. Other raptors that use witches' brooms as nesting sites include great gray
owls, long-eared owls, goshawks, and sharp-shinned hawks. Likewise, some
migratory birds also nest in witches' broom -- gray jay, northern
beardless-tyrannulet, red crossbills, house wrens, mourning doves, pygmy nuthatches,
chickadees, Western tanagers, chipping sparrows, hermit thrushes, Cassin's finches,
and pine siskins. "A well-disguised nest provides protection against
predators such as the great horned owls," Bennetts said.

Bees, Butterflies, and Others
According to butterfly expert and Colorado State University professor Paul
Opler, three kinds of butterflies in the United States are entirely dependent
on mistletoes for their survival: the great purple hairstreak, the thicket
haristreak, and the Johnson's hairstreak. The great purple hairstreak, says
Opler, is the only butterfly in the United States that feeds on American
mistletoe, the Christmas mistletoe. This beautiful butterfly lays its eggs on the
mistletoe, where the resulting caterpillars thrive one a mistletoe diet. The
caterpillars of the other two butterflies feed on dwarf mistletoes. The Johnson'
s hairstreak, restricted to just the Pacific states, is usually found in
association with old-growth conifer forests, the same places spotted owls
prefer. The caterpillars of these butterflies closely mimic the appearance of the
mistletoe with their mottled green and olive shades. Like people, the
butterflies of these species use mistletoe for courtship rituals. After courting and
mating in the mistletoe high in the canopy, the adults leave their eggs
behind in the mistletoe. The adults of all three species drink nectar from the
mistletoe flowers. Mistletoe is also important nectar and pollen plant for
honeybees and other native bees, says Erik Erikson, a bee researcher at the USDA
Bee Research Lab. Mistletoe flowers, says Erikson, often provides the first
pollen available in the spring for the hungry bees. "We look upon it as an
important starter food source for the bees," said Erikson. Wind and insects are
important mistletoe pollinators. Although hundreds of kinds of insects carry
mistletoe pollen, only a few dozen are important pollinators; these include a
variety of flies, ants, and beetles. Yet other insects eat the shoots,
fruits, and seeds of the mistletoe, including some that feed exclusively on the
plant. Exclusive mistletoe-eaters include a twig beetle, several thrip species,
and a plant bug whose coloration mimics dwarf mistletoe fruits. In addition,
at least four mite species seem to be exclusively associated with dwarf
mistletoe.

And Then There's the Mammals
Don't try it at home, kids and grown-ups -- mistletoe is toxic to people,
but the berries and leaves of mistletoe provide high-protein fodder for many
mammals, especially in autumn and winter when other foods are scarce.
Researchers have documented that animals such as elk, cattle and deer eat mistletoe
during winter when fresh foliage is rare. In Texas, some ranchers even consider
mistletoe on mesquite as an insurance forage crop, which the ranchers remove
from the trees for cattle food when other forage is scarce. Other mammals
that eat mistletoe include squirrels, chipmunks, and even porcupines, some of
which are deliriously fond of the plant. A variety of squirrels, including red
squirrels, Abert squirrels and flying squirrels often use witches brooms for
cover and nesting sites.

A Blessing or a Bane?
Not everyone likes mistletoe. Many commercial foresters consider the dwarf
mistletoe as a disease that reduces the growth rates of commercially important
conifer species, such as the ponderosa pine. Ecologists, though, point out
that mistletoes are not a disease; instead, they are a native group of plants
that have been around thousands, or even millions, of years. Blessing or
bane, it is certain that mistletoe is not spreading like wildfire -- in fact,
mistletoe spreads only about 2 feet per year. One study indicated that a
1.5-acre patch of mistletoe took about 60 to 70 years to form. Likewise, the death
of an individual tree from dwarf mistletoe may take several decades, and
widespread infestation of a forest stand may take centuries. Bennetts believes
that the conflict with forest management and the perspective of mistletoes being
a forest disease really only comes into play when the management objectives
are to maximize timber harvest. Otherwise, he says, mistletoes have many
positive attributes, including tremendous benefits for native wildlife. Thus, he
says, when not in conflict with commercial timber management objectives,
mistletoes should be viewed as a natural component of healthy forest ecosystems.
Says Bennetts: "I had the privilege of working with a biologist who had spent
more than 50 years working on mistletoes. He began his work with the intent
of finding a way to control this 'forest pest,' but in his later years, he
even introduced dwarf mistletoe to some of the trees in his yard because he
had grown to love this plant for what it is . . . a fascinating and natural
part of forest ecosystem."

For More Information Contact:
Catherine Puckett
email: catherine_puckett@usgs.gov

Todd Esque
email: todd_esque@usgs.gov 

The USGS serves the nation by providing reliable scientific information to
describe and understand the Earth; minimize loss of life and property from
natural disasters; manage water, biological, energy, and mineral resources; and
enhance and protect our quality of life.
***USGS***

More information on mistletoe:

Genus: Phoradendron
USDA-NRCS PLANTS Database (2007)
http://plants.usda.gov/java/profile?symbol=PHORA 

Non-wood products from organisms associated with temperate broad-leaved
trees: Mistletoe
Ciesla (2002)
http://www.fao.org/DOCREP/005/Y4351E/y4351e0d.htm 

State trees and state flowers
U.S. National Arboretum (2006)
http://www.usna.usda.gov/Gardens/collections/statetreeflower.html 

What Does Mistletoe Have To Do With Christmas?
Tainter, Frank (2002)
http://www.apsnet.org/online/feature/mistletoe/ 

'Tis the Season for Mistletoe
MSU Extension Service (1997)
http://msucares.com/newsletters/pests/infobytes/19971202.htm 

Mistletoe: Good for More Than Free Kisses
HerbalGram. 2005;68:50-59 American Botanical Council
http://content.herbalgram.org/youngliving/herbalgram/articleview.asp?a=2901 

== 3 of 3 ==
Date: Sat, Dec 22 2007 8:58 pm
From: James Parton


Russ,

I myself was reading on mistletoe just a couple of days ago. It really
is a fasinating plant. This post is a great blend of facts & mistletoe
traditions rolled into one. Great!

James Parton.

See also Pliny;s Natural History