Silver Sword
The silver sword is a shrub that is endemic to the Hawaiian Islands. The botanical name of this plant is Argyroxiphium caliginis. Since it is only found in Hawaii, the silver sword is not an invasive species. (To the left: Map showing Hawaii as habitat. www.plants.usda.gov) According to The Ecology of Plants: 2nd edition, the silver sword is considered an annual plant; it reproduces once in its lifetime. However, there have been rare cases where this plant has flowered repeatedly. This shrub gets its name from the “silver-like” leaf tips. Those leaves are used in helping the plant survive. According to www.kaahelehawaii.com, a web site dedicated to Hawaii’s native plants, the silver sword is strong enough to withstand the most brutal mountain storms and also the blazing heat throughout the summer.(Middle picture: silver-like leaf tips. http://images.jupiterimages.com/common/detail/77/36/23453677.jpg) But, be careful! Even though the silver sword can deal with practically any kind of temperature, one reason why it is an endangered plant is because of humans. Reported by www.kaahelehawaii.com, this shrub is so delicate that oil from human skin or your finger tip can damage the fine hairs on the silver sword which protect it from dehydration and too much sunlight. Not only that, if you come across a silver sword do not get too close. The shrub’s roots are located right under the surface and the weight from people’s feet can crush the brittle roots.
How big does a silver sword grow?
Usually, a silver sword will reach about half a meter in diameter. Once it has reached that size, flowers will blossom that can reach up to two meters tall, as reported by www.kaahelehawaii.com. (To the right: Full grown silver sword with flowers. http://www.dkimages.com/discover/previews/921/50196258.JPG)
How have humans used this plant?
According to www.kaahelehawaii.com, people have used the silver sword for their own use. However, none of the usages seem to be reasonable. People have uprooted these plants for “dry arrangements”, to start fires, and sometimes just for sport. Because of this, the silver sword is an endangered plant in Mauna kea, Mauna Loa, and Haleakala.
Other random facts about the silver sword shrub
Since the silver sword population lives in Hawaii, it has to do deal with some very dry conditions. According to Plants: Diversity and Evolution, the silver sword shrubs have large “water-retaining gels” in their inter-cellular spaces. The gels act as water storage for the silver sword.
The Biome of a Silver sword
The silver sword is a shrub that is native to the Hawaiian Islands. Because of the dry climate it lives in, the silver sword is part of the “Tropical and Subtropical Grasslands, Savannas, and Shrublands” biome. According to www.worldwildlife.org, this shrub lives on some of Hawaii’s highest peaks in alpine deserts which can have some of the coldest and some of the hottest weather conditions. They can survive in habitats such as “exposed lava, dry scrub, dry woodland, moist forest, wet forest, and bogs” as stated in the Biology of Plants by Peter Raven. In all of those habitats, the yearly precipitation can range from 40 centimeters to more than 1230 centimeters (Raven210).
The silver sword, Argyroxiphium caliginis, is found mostly on the “upper cinder slopes of Haleakala Crater on the island of Maui” (Raven210). At this location, the shrub becomes exposed to very high levels of solar radiation and very low humidity (Raven210). Through the extreme weather conditions, the silver sword is a great example of adaptive radiation. This is the process in which a species changes its characteristics to fit its new habitat (Raven210).
The silver sword shrub gets its name from the silver-like hairs. The hairs protect the plant from strong solar radiation (Raven211). Not only that, but they also help the plant conserve moisture (Raven211). The green sword, Argyroxiphium grayanum, which is also found in Hawaii, does not have the silver hairs (Raven211). However, the green sword lives in wet forests (Raven211). Because it does not live in such a dry environment, it does not need the hairs because it does not have to deal with as much solar radiation.
Since the weather can change so much, silver swords have to be ready for different environmental challenges. The dryer the environment is, the greater the tolerance to water stress will be (Raven211). Plants that live in wet or moist habitats will not have such a great tolerance. Also, the dryer the habitat, the more elastic the cell walls are on the leaves (Raven211). This will enable plants to maintain a “higher turgor pressure” than its relatives under a dry condition (Raven211).
It has been reported by www.kaahelehawaii.com that a silver sword begins to flower when it reaches a diameter of about half a meter. Once the flowers are present, the shrub is ready for pollination. The silver sword is pollinated by flying insects (www.kaahelehawaii.com). To prevent crawling insects from reaching the pollen and nectar, the flower area is covered with “sticky glandular hairs” (www.kaahelehawaii.com). If any insect tries to crawl in, they will get caught on the hairs and not be able to reach the nectar. A healthy silver sword is capable of producing thousands of seeds on a single stalk (www.kaahelehawaii.com). However, it will die shortly there after. If the stalk is damaged before re-seeding, it will not produce anymore seeds (www.kaahelehawaii.com).
There are certain things other than humans that pose as a threat to the silver sword community. Since it is such a dry area, wildfires are known to be a threat, according to www.worldwildlife.org. Also, whenever new plants are introduced into a new environment, they are considered to be competition. With more and more plants in a certain area, only the strong will survive.
Since the silver sword shrub is only found in one place on earth, we must do our best to keep it from extinction. Humans pose as a threat because of recreational activities performed close to the plant. Be careful what you do; the silver sword is such a unique shrub and we must do all we can to help the population grow.
Why did I choose the silver sword?
I have not studied plants too much so I did not have any idea of what plant to research. After seeing a picture of a silver sword in class, I realized how cool and how unique this plant looks. Also, I have never been to Hawaii but it has always been somewhere I have wanted to travel to. If I ever am fortunate enough to go to Hawaii I will make sure to check out the silver sword!
Works Cited
Gurevitch, Jessica and Samuel M. Schneider and Gordon A. Fox. The Ecology of Plants: Second Edition. Sunderland (MA): Sinauer Associates, Inc. p.118-119.
Ingrouille, Martin J. and Bill Eddie. Plants: Diversity and Evolution. Cambridge (UK): Cambridge University Press. p. 307-308.
Raven, Peter H. and Ray F. Evert and Susan E. Eichhorn. Biology of Plants: Seventh Edition. New York: W.H. Freeman and Company. p. 210-211.
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