Salt Lake City watershed specialist Vanessa Welsh sat in the shade of a tree near a trail above City Creek Canyon on Saturday and spotted what seemed like a harmless flower. Instead, she described the plant as an invader.

"They're everywhere and they push other native plants out," she said of Dyers woad.

By early afternoon the plant, and many more like it, were dead invaders thanks to 100-plus volunteers who spent the day toiling on trails above the canyon.

While many volunteers spent hours yanking invasive plants with such exotic names as myrtle spurge and dalmation toadfax, others spent the day removing rocks and widening trails.

The volunteers were organized by the Bonneville Shoreline Trail Committee for National Trails Day, an event launched in 1993 to promote use and awareness of the outdoors.

Saturday events were held in Ogden, Sandy and Salt Lake City, with the area above City Creek in the Morris Meadows region getting some particular TLC. Since it's so close to the city and is used by an average 300 to 500 people a day, in the estimation of trail builder Bob Piscopo, the area was in dire need of an overhaul.

Volunteers huffed and puffed their way up the trail, removing rocks, adding fill dirt where needed and widening the trail to four feet.

"We're trying to bring it up to speed without having to totally rebuild it," said Piscopo, who works with the Salt Lake Ranger District. "These volunteers out here are saving us a lot of time and money."

One of them was John Haigwood, whose shirt was wet with sweat despite the cool morning air and steady breeze as he guided a wheelbarrow full of gravel -- to fill in low spots -- up and down the trail.

Haigwood considered the effort part of his civic duty.

"Someone needs to do it, otherwise all of this just goes away," he said, looking at the network of trails that wind through the meadow. "Hauling rocks is good for me. I've met new people and at the end of the day it feels good to give back."

Salt Lake City watershed ranger John Wells said the goal was making the trail more family-friendly. Mountain bikers who enjoyed testing their technical skills on the rocks that littered the trail might not approve, but it's necessary work in an area so close to the city, Wells said.

"This area gets a lot of mixed use, a lot of family use," Wells said. "We wanted something that will attract grandma and grandpa up here."

Hopefully while they're up there, they'll snatch a few weeds out of the ground. too. At least, that was the ideal scenario for Welsh.

"I figure if they spend several hours pulling up a weed, they'll recognize it the rest of their life," she said. "I've had people tell me I've ruined them, but the idea is to keep maintaining this area. We're trying to maintain biodiversity, and this could be a good example of how it can work."

The long-term goal of the Bonneville Shoreline Trail Committee is to stretch the trail from Nephi to Tremonton, creating a 280-mile trail network. Now, fewer than 90 miles are designated as Bonneville Shoreline Trail, but taking care of what exists is as important as building more trails in the future, Wells said.

"We could use more people out here like this," he said.