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.