Yucca
glauca
Photo
taken
June 10, 2000
Turkey Canyon Ranch
, CO
SPECIES:
About 30 species in the genus Yucca are found in
North America
.
Only Yucca glauca is common and native to the western great plains.
It is found from
South Dakota
down through western
Nebraska
,
Kansas
, and
Oklahoma
.
Because of the lack of moisture, plants are spaced out across the
dry semi-arid hills. Yucca
glauca only produces from 20-60 white flowers per stalk.
The common yucca found around towns and graveyards in the eastern
plains and across the Midwest
is Yucca filamentosa.
Also known in nursery catalogs as Yucca smalliana, Y. filamentosa
is a cultivar that is native to the humid southeastern
U.S.
It occurs in the central
U.S.
only where planted and disperses
only a short distance from where it was planted.
The greatest variety of yuccas live in the southwestern
U.S.
where they evolved as successful
semi-desert plants.
Arizona
is home to 14 species, including
the Spanish bayonet and the Joshua tree.
There are also many yucca moth species in that area to pollinate
the wide range of yucca species. Because
of the great variety of yuccas and their moths in the southwestern
U.S.
, biologists believe this is the
region where most of the evolution of these groups occurred; a process
called adaptive radiation.
Yuccas have co-evolved with their moths.
The yucca plant has not ability to reproduce seeds without the
moth. Yuccas can propagate
small rosettes around the parent plant, but these vegetative sprouts are
copies of the parent. Over
decades, the plant cannot move but a few feet, and there is no possibility
for genetic variation. Without
the moth, the whole flowering effort is a total waste.
The only pollinator of the plant is the yucca moth; bees are not
attracted and neither wind nor bees can pick up the sticky pollen.
The
yucca moth is likewise dependent on the yucca plant.
There are no alternate host plants known for the yucca moth; the
yucca mother caterpillars must eat yucca seeds or starve.
Without the plant, the moths die off in one generation.
Without the moth, the plant cannot reproduce variation or disperse;
give any major climate changes, it too will go extinct.
It is a tight system of co-evolution.
You can watch yucca moths pollinate flowers between dusk and
midnight
(though I have not seen this).
The female gathers pollen from the flower anthers by using he
specially adapted mouthparts, called palps.
She forms the sticky pollen into a ball, which she carries under
her chin. The pollen ball is
then stuffed or combed into the stigma of the various flowers she visits.
The stigma is the receptive tip of the female pistil.
Without this process, the yucca flower will not develop into the
fruit or pod with seeds.
It has been speculated by biologists that ancestral yuccas were plagued
with small moth caterpillars that fed inside plant shoots.
As with modern moths, there is some variation in each generation,
and a few eggs are laid beyond the stems on blades and flower parts.
Eggs laid in fertilized flowers discovered an untapped developing
supply of seeds rich in protein, and their young survived in high numbers
and reinforced this population of flower-inhabiting larval moths.
The variant larval moths that ate seeds added a burden to the
plant, but moths that moved from flower to flower also carried pollen with
more accuracy than casting pollen to the wind.
Such a tradeoff, perhaps only slightly in the plant’s favor at
first, became even greater as moth variants became more skillful at
transfer of pollen, especially by selection for palps and behavior to comb
the yucca pollen from anthers. Meanwhile,
the yucca could save much energy by forming pollen that is gummy rather
than fine and wind dispersed.
HISTORY: New Mexico
selected the Yucca glauca as its
state flower in 1927. It is
sometimes called Spanish bayonet for its long, sharp leaves. Other
nicknames are beargrass and soapgrass.
Yuccas are native to the
West Indies
and the word yucca comes from the
island
of
Haiti
.
One of its species, the Joshua tree, can grow as tall as 30 feet.
HISTORIC USE: The yucca has a
long history of use as a folk remedy employed for treatment of arthritis
and rheumatism and is cultivated as an important medicine plant and staple
food in
South America
.
Native Americans used the soapy leaves from yucca as poultices or
for baths for skin sores and sprains as well as to treat burns and
abrasions. Inflammation
of all sorts, including joint inflammations and bleeding were also treated
with yucca. Some report that
Native Americans washed their hair with yucca to fight dandruff and hair
loss. Black ashes of yucca
were made into a paste by mixing them with water.
The paste was smeared over the entire body to help break a fever.
PARTS USED: The stalk, root,
and leaves are commonly used.
ACTIVE
CONSTITUENTS: The saponins
from yucca are the main medicinal agents in the plants.
They have both a water-soluble and a fat-soluble end and therefore
act like soap.
PREPARATIONS & DOSAGE: One-quarter
ounce of the root can be boiled in a pint of water for 15 minutes.
Under guidance of your herbalist, three-five cups of this tea can
be taken per day. It can cause
loose stools in some who should simply reduce the dose.
Two-four capsules per day is also a common dose.
ACTIONS: The yucca root is
rich in steroid-like saponins that elevate the body’s production of
cortisone, possibly explaining the herb’s ability to aid in arthritic
pains. Saponins also provide
anti-inflammatory relief as well as the ability to break up inorganic
mineral obstructions and deposits. Yucca
also has laxative properties and is also used to establish a flora balance
in the GI tract. It is also
speculated that yucca saponins block release of toxins from the
intestines, which inhibit normal formation of cartilage.
Both leaves and root function well as diuretics and emetics.
Extracts from one species of yucca has been found to fight melanoma
cells in test tube studies.
PRECAUTIONS & ADVERSE REACTIONS:
Yucca and other saponins can cause red blood cells to burst (known
as hemolysis) in test tubes. The
level to which this occurs when the saponins are taken by mouth is
unknown. Yucca has also been
known to cause stomach distress and to be useful to induce vomiting.
However, yucca is approved for use in foods as a foaming agent
(particularly in root beer). Since
there have been no reports of problems with hemolysis in root beer
drinkers, we can assume that yucca herbal supplements are generally safe.
CLINICAL USE: Yucca root is a
therapeutic anti-inflammatory phytosterol.
Its primary use has been in pain relief for arthritic and joint
pain and sediment caused by inflammation such as gout, rheumatism, and
cystitis. It also has
moisturizing qualities, is a potent anti-irritant and has
hair-strengthening capabilities. Studies
have shown that yucca extracts increase the moisture content of the skin
by 22% and increase the smoothness of skin by 48%.
A yucca extract evaluated on 10 individual strands of hair
increased break strength by an average of 43% and elasticity by an average
of 62%. Yucca may also be useful for the GI tract, as a laxative and to
re-establish normal flora balance. It
has also been used to for asthmatic relief.
