The menace most likely to lay waste to the cherished forests of Point Defiance Park is a plant. A pretty one, at that.
The shiny, pointed leaves of Hedera helix, more commonly called English ivy, make for a deceptively lush carpet.
But this wolf in sheep’s clothing has overrun slopes and gullies on the east side of Point Defiance. Despite volunteer efforts to beat it back, ivy threatens to sack other undeveloped areas.
“Ivy is proving to be the most ominous threat to our woodlands. … If we want natural Douglas fir and hemlock forests in the future, the ivy must be controlled,” says a 1995 Point Defiance forest management plan.
Ivy is what weed-control experts call an invasive species, a botanical bully that dominates its surroundings, smothering less tenacious native plants. Left unrestrained, mature ivy strangles trees.
“It kills everything in the understory. That’s the worst thing. Nothing can out-compete it,” said Robert Van Pelt, a University of Washington forestry expert.
The 1995 report recommended that park managers cut out ivy from trees and remove it and other nonnative plants from the park’s forests.
No one has documented the extent of the ivy trouble. But the plant is a far more forbidding enemy than other invasive species, those familiar with the park said.
“I swear it grows 5 feet in a day. It’s horrible,” said Bill Hicks, chairman of the American Rhododendron Society’s Tacoma chapter.
For the most part, ivy removal has been left to groups of ardent volunteers, primarily American Rhododendron Society and Sierra Club members, who have devoted hundreds of hours to the job.
“I would like to see more ivy pulling, but it’s a never-ending task,” said Kathy Van Pelt, Metro Parks urban forester and Robert Van Pelt’s former spouse.
Other aggressive, nonnative plants also endanger native species. Patches of nasty Himalayan blackberries and persistent Scotch broom grow in the sun. Holly and Herb Robert – also known as stinky Bob, a member of the geranium family – thrive in the shade.
Stinky Bob is the scourge of Tacoma’s Swan Creek Park, where Washington Native Plant Society volunteers have tried to root it out.
“Once you get it really bad, it’s almost impossible to control,” said Catherine Hovanic, plant society administrator, who lives in Fircrest. “It should be a real priority for … (Point Defiance) to go after those small populations while they still can.”
In Point Defiance, volunteers attack ivy and other invasive plants at least once a month. Climbing ivy vines are the No. 1 target, said Bliss Moore, chairman of the Sierra Club’s Pierce County chapter.
“I’m one of those gung-ho people that likes to pull that stuff,” he said. “You can actually cut its lifeline and it will die.”
Moore has lived across the street from Point Defiance Park for more than 17 years. The heart of the park’s forest is still unspoiled, but he said the ivy creeps on.
“When it gets entrenched, it’s a matter of controlling and not eradicating it,” Moore said.