Saturday, April 14, 2007

Maxwell's Silver Sword

My parents just came back from a cruise in Hawai’i1, and I felt compelled to ask if they found any exciting wildlife. They had, in fact, found a plant with this blog in mind. Instead of saddling Florabot with this one, I figured I’d write my first plant post.

Image from Dad
Image by Dan Yaussy

The Hawaiian Silversword (Argyroxiphium sandwicense) is a spiky, once-flowering relative of asters and sunflowers. There are two subspecies, the Halekala Silversword (ssp. macrocephalum), shown above, and found on Maui, and the Mauna Kea Silversword (ssp. sandwicense), which is found on that mountain on the Big Island. There are some differences between the subspecies. This means, that to tell which one you’re looking at, it helps to have a botanist and a dichotomous key.

The Silversword gets its name from the sharp, sword-like leaves that are covered with silvery hairs. These hairs reflect the hot Hawaiian sun, cooling down the plant, and the bristly leaves protect the center from predation. They grow on the sides of volcanoes with very shallow roots. They spend fifteen to fifty years growing as a short, sharp rosette, and then send a single stalk up to nine feet high with fifty to six hundred flowers2, set seed, and die.

Since the roots are so shallow, goats, sheep, and cattle easily uproot this plant when trying to eat it. Other invasive species, like Argentine ants, are also causing problems. Hikers can accidentally do same, or intentionally. Apparently, hikers used to pick them as proof they climbed the mountains where they grow. There’s no information on when “used to” was.

Lots of people are working on saving this prickle-ball. For example, people at the University of Arizona are currently working on making sure the Mauna Kea Silverswords don’t become terribly inbred after only a few were saved in the late ‘70s. Also, better signage and visitor education has helped remove some threats.

1I suppose I really can’t complain.
2They’re fairly small flowers.


IAMB said...

If I remember correctly from my last visit, the pigs also play hell with the plant... just like they do with every other damn thing on the islands. It's really too bad, since Hawaii has some of the most interesting wildlife anywhere on the planet if you're a guy like me (carnivorous inchworms kick ass).

Greg said...

Hey, thought you might find these articles interesting . . .

The Province
Edmonton Journal