Alien plants pushing natives out of New York

Exotic trees, vines and shrubs have taken root and are prospering

Pipsissewa `gone, just gone'

April 30, 2001|By Barbara Stewart | Barbara Stewart,NEW YORK TIMES NEWS SERVICE

NEW YORK - The survey is not even halfway done, yet it has already revealed a disturbing trend: Immigrants are forcing old-timers out of their homes.

"The native plants that used to be here are being pushed out by development and aggressive non-native plants," said Gerry Moore, a botanist with the Brooklyn Botanic Garden.

The Brooklyn garden is cataloging every variety of plant life in the New York metropolitan area. That flora project, a comprehensive effort to determine what plants exist in a 7,650-square-mile area of New York City, northern New Jersey, Long Island and Westchester and Orange counties, is 10 years old.

The survey is expected to take another 10 to 20 years to complete.

After finding and identifying the plants, the researchers compare them with 100 years of historical records to see what is new, extinct, declining or increasing.

The results so far do not bode well for many native plants.

At a ditch next to Hurley Pond Road in Howell Township, in a rural section of Monmouth County, N.J., Steve Glenn, a project botanist, stepped over beer cans and into the scraggly scrub, his eyes trained on the ground. Across the road, Moore pushed through the bushes with seven wild cranberries in his hand.

`A rare one'

Glenn bent over a thin-stemmed reed with blue-green leaves and brown-and-yellow tips. "A Carex barattii, Steve!" Moore said. "That's a rare one. Amazing. Plants like this are just hanging on by their toenails."

The first category of the study - trees, shrubs and vines - has been completed. A handful of botanists and scores of volunteers have cataloged about 450 species in the metropolitan area.

Now they are working on wetlands and aquatic varieties, which number about 1,200. Next are the 2,700 types of grasses, and then ferns, wildflowers and weeds.

When it has concluded, the project will start over from the beginning, cataloging the same places to see what has changed.

Researchers hope that the survey will help them answer questions: Is it possible to track the decline in native species? How many Southern plants are spreading north, perhaps as a result of global warming? Most important, how can native species be brought back to the city and the region?

The survey has already documented the growing dominance of imported plants. The ditches by Hurley Pond Road in Howell Township provided a good example.

On one side, dark-green patches of Asian pachysandra flourished; on the other, Japanese honeysuckle was entwined with the shrubs and trees. Along the road were several swaths of land that had been cleared for construction.

One-third non-native

Throughout the region, many varieties of exotic trees, shrubs and vines that have taken root over the years are proliferating. Unlike the native species, which tend to grow more slowly and in one kind of habitat, the alien plants grow rapidly and thrive in varied habitats.

About one-third of the plants in the New York area are non-native, and some are spreading so rapidly that they are squeezing out and nearly annihilating the native ones, botanists say.

One newcomer, Oriental bittersweet, was first raised in private gardens and botanical gardens in the late 1800s.

Now that vine, with its brilliant orange fruit, is everywhere. It twists around trees and strangles them, in parks and forests and along highways.

The multiflora rose, an Asian import with delicate white blossoms, was once a flower of choice for many gardeners, and was used for erosion control. Now, it blankets summer meadows that used to be yellow, pink and blue with goldenrod and asters, and it pushes up through asphalt cracks.

"Everywhere," Moore said. "A terrible weed."

Phragmites and its smaller cousin, stiltgrass, have become a horror story for parks managers. Nearly every water bank and marsh in the region is surrounded by towering phragmites. The phragmite reeds choke ponds and lakes with roots that extend 6 or 8 feet into the ground.

Planting a monoculture

Robert Moses, the New York City parks commissioner from 1934 to 1960, was among those who planted tough foreign strains of phragmites in wetlands, which were considered disease-ridden swamps.

"It grows so aggressively that nothing can take it on," Moore said.

Wetlands where orchids once grew and lakes that had wild rice and cardinal flowers are clogged with phragmites and stiltgrass.

As Glenn pushed through chest-high reeds, he said disgustedly, "This phragmites has become nothing but a monoculture."

There are more invaders. Black locust trees, which were imported for ship masts, and tree of heaven, intended as food for silkworms, are all over, pushing their way through concrete and thriving in poor soil.

Floating water chestnut is taking over the Hudson and Delaware Rivers, and flashy purple loosestrife is crowding out native wildflowers in wetlands and meadows.

Gone without a trace

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