In the early 1870s an enterprising nurseryman in Southern California imported a tall, clumping grass with distinctive feathery plumes to his ranch. Over the next several decades he created an entire industry for the plumes of the plant called pampas grass. At the height of the plume boom, he was exporting 500,000 plumes a year throughout the United States and Europe, influencing Victorian-era fashion. By the close of the 19th century, pampas plumes were dyed different colors to fill vases, decorate women’s hats, and cover parade floats. Eventually the trend ended, but pampas has been used in landscaping ever since.
This invasive grass is anything but fashionable. Now, rather than topping hats and decorating parade floats, the ten-foot-tall feathery plumes top clumps of razor sharp leaves throughout California. Pampas grass blocks beach access, fuels wildfires, and invades native ecosystems. Introduced to Maui in the 1920s, pampas has proven invasive here as well.
There are two species in Hawaii known as pampas grass, Cortaderia selloana and Cortaderia jubata. Both species of pampas grass have been planted widely in landscaping throughout California; now every backyard population has become a seed source for this invasive plant. Both species are also found on Maui and jubata has become extremely invasive. It finds a foothold in any bare soil or disturbed areas, and has invaded many different ecosystems from the dry rocky soil in Haleakala Crater, to the boggy rainforest of East Maui, and the eroded cliffs of West Maui. Control of jubata first began in 1989 by staff of Haleakala National Park and is continued by Maui Invasive Species Committee (MISC). Field crews attack pampas any way they can, hovering along cliffs with helicopters, camping in the rainforest for weeks, knocking on doors, and lining up across the slopes of Haleakala to search for the distinctive plumes.
But efforts to control the invasive Cortaderia selloana have been stymied by a confusion that began in California in the 1970s. When pampas grass was first recognized as being invasive, scientists thought C. selloana was only slightly weedy, whereas its cousin, Cortaderia jubata, was deemed to be an immediate and serious threat based on its ability to reproduce.
A single jubata plant can readily produce fertile seed with no need for pollination. The downy light seeds float on the wind and jubata quickly escapes garden plantings. The selloana plant, however, requires both a male and female plant to produce fertile seed. Resource managers thought that only female plants were on Maui, making selloana a safe landscaping alternative to jubata because it wouldn’t be able to spread. But C. selloana turned out to be a wolf in plume’s clothing. A keiki selloana was found on Maui in 2006; the identification was confirmed by genetic analysis of a sample sent to the University of California-Davis, establishing that selloana is reproducing here.
Given evidence from California we can expect that selloana will be an even more aggressive invader than jubata. Over the past 60 years in California, the selloana population has expanded twice as fast as jubata. Selloana is increasingly able to invade native vegetation.
What was the “good” pampas in Maui backyards is now recognized as an invader lurking on the horizon. Please do not grow any kind of pampas grass on Maui. If you know of a population of pampas grass, or have it on your property, please call MISC (573-MISC) to have it removed free of charge.
Article by Lissa Fox Strohecker
Originally published in the Maui News, September 12th, 2010 as part of the Kia‘i Moku Column.
You can find all the articles in the Kia‘i Moku series http://www.hear.org/misc/mauinews/