invasive ornamental grasses — Maui Invasive Species Committee (MISC)

Steve Perlman examining invasive pampas grass in Kauaʻula Valley. — MISC file photo

With plumes that bring to mind ostrich feathers, pampas grass first became popular in the Victorian era. Fluffy seed heads decorated the most fashionable hats, homes, even carriages. Interest surged again in the mid-1960s and the plant became a fixture in some yards and golf courses on Maui.

Today, pampas is taking over Instagram feeds: the plumes are used to add a Bohemian/Southwestern flavor to wedding bouquets, centerpieces, and home décor. But here on Maui, this ornamental grass is associated with a different trend: loss of habitat for threatened and endangered species and destruction of the watershed.

“But here on Maui, this ornamental grass is associated with a different trend: loss of habitat for threatened and endangered species and destruction of the watershed.”

Pampas can grow on nearly vertical slopes, displacing native plants that support populations of threatened and endangered animals and disrupting watershed function. With seeds that can travel 20 miles in the wind, ornamental plantings can infest far away forests. — MISC file photo

Pampas is a clumping bunchgrass native to South America. The leaves are razor-sharp, dying back each year but leaving dry foliage that accumulates and can fuel wildfires. The decorative plume is the seed-head and a single plant can spread millions of tiny seeds on the wind – in some cases, as far as 20 miles. Seeds germinate readily on bare soil, but with enough moisture, the invader finds footholds in patches of moss or tree bark. The plant competes with native vegetation and could replace habitat and food resources used by native birds and in doing so disrupting the layered structure of the rainforest so important for aquifer recharge.

This grass knows no limits – it has been found growing from sea-level to the rim of Haleakalā Crater at 9000 feet. Water, or lack thereof, doesn’t seem to be a key determinant for where pampas lives. It will (and does) grow in the wettest rainforests and on the driest hillsides, often emerging in rain-drenched bogs and wind-scoured cinder slopes.

Pampas grass has been a target for eradication on Maui since the mid-1990s when staff from Haleakalā National Park started finding feathery plumes in the crater. MISC has been working to stop pampas since the inception of the program. Through continued control efforts, the East Maui population has been in steady decline but without consistent support and control efforts, progress could stall.

MISC employee scoping out pampas. Invasive plants don’t always grow in easily accessible areas. The slopes of West Maui are so steep that efforts to remove plants like pampas grass necessitate the use of helicopters. — MISC file photo

The West Maui pampas population has always presented challenges. Much of the difficulty lies in the rugged terrain and weather, limiting access for much of the year. On East Maui, crews can access much of the known pampas infestation by timing helicopter flights early in the day and camping and hiking to access plants from the ground, but the slopes of the West Maui Mountains are more vertical than anywhere else in Maui, affording few camping sites and making ground access difficult or impossible. Pampas, on the other hand, thrives on the bare soil of the erosion-prone slopes. When that happens, our crews depend on helicopters to seek out and remove the invader.

Thanks to funding from the National Fish and Wildlife Foundation, MISC crews have been scouring the cliff faces of West Maui over the last year. They are looking for pampas plumes and the tell-tale growth pattern of the plant before it goes into flower. If they find the plant, they record the location by on a GPS and then return by helicopter but this time loaded down with an external tank and 80’ long line and weighted sprayer attached. This allows the pilot and crew to hold hover over the plant and remotely trigger a tiny spray of herbicide directly to the grass below.

Despite nearly constant rescheduling of flights due to weather or a need for the helicopters to go fight a brush fire, crews have flown over 15,000 acres on West Maui from 2017 to the summer of 2019. This coverage has led to the detection and removal of nearly 1,900 pampas plants from the mountain slopes– a huge leap forward in the effort to stop this invader from taking over prime habitat for native birds, plants, and invertebrates.

You can help. First, become familiar with what pampas grass looks like (mauiinvasive.org/pampas/). Second, never plant pampas grass or import it for décor or floral arrangements. The Division of Forestry and Wildlife has designated pampas as one of Hawaiʻis most invasive horticultural plants. Finally, report any pampas grass you find. You can report it to MISC: 573-6472, miscpr@hawaii.edu, or online at 643PEST.org

Lissa Strohecker is the public relations and education specialist for the Maui Invasive Species Committee. She holds a biological sciences degree from Montana State University. Kia’i Moku, “Guarding the Island,” is prepared by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that can threaten the island’s environment, economy, and quality of life.

This article was originally published in the Maui News on September 14th, 2019 as part of the Kia‘i Moku Column from the Maui Invasive Species Committee.

Read more Kiaʻi Moku articles.

Pampas grass plumes were once so popular they even decorated parade floats, such as this 1st prize winner in a parade in Colorado at the turn of the century. Photo courtesy of Denver Public Library, Western History Collection.

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 19^th 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.

This stand of Cortaderia jubata plant, or pampas grass, was found in Haleakala Crater and removed in 2008. Pampas grass is an invasive species, and a variety thought not to be a local threat at one time has turned out to be one. Maui Invasive Species Committee photo.

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/

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